castle douglas flood risk assessment - dumgal

CASTLE DOUGLAS

FLOOD RISK ASSESSMENT

REFERENCE: DG/CB/190/11

FOR

DUMFRIES AND GALLOWAY COUNCIL

&

SCOTTISH POWER

Name Signed Date

Author William Hume 12th

September 2013

Checked By Steven Curran 12th

September 2013

Report No. 1168-202 Version: FINAL

Type Flood Risk Assessment Level Level 3

Revision: 1 Issue Date: 12th

September 2013

CASTLE DOUGLAS


FOR

DUMFRIES AND GALLOWAY COUNCIL & SCOTTISH POWER

TABLE OF CONTENTS

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J:\Jobs CDH\1100-1199\1168 - Dumfries & Galloway Council\1168-202 - Castle Douglas\7 - Reports\1168-202 Castle Douglas FRA FINAL Rev 1.doc

1 INTRODUCTION ....................................................................................................................... 1

1.1 PREAMBLE ...................................................................................................................... 1

1.2 OBJECTIVES OF INVESTIGATION ........................................................................... 2

1.3 REPORT STRUCTURE ................................................................................................... 2

1.4 LIMITATIONS OF REPORT ......................................................................................... 2

2 DATA SOURCES, GEOGRAPHY & HYDROLOGICAL ENVIRONMENT .................... 3

2.1 DATA SOURCES .............................................................................................................. 3

2.2 GENERAL GEOGRAPHY OF THE CASTLE DOUGLAS AREA ............................ 3

2.3 GENERAL GEOLOGY ................................................................................................... 4

2.4 HYDROLOGICAL ENVIRONMENT ........................................................................... 4

2.4.1 Galloway Hydros Scheme ................................................................................................. 4

2.4.2 Hydrological Impact of Hydro Scheme ............................................................................. 5

2.4.3 Impact of Water Framework Directive on the Hydro Scheme .......................................... 5

2.4.4 Carlingwark Lane .............................................................................................................. 5

2.4.5 Carlingwark Loch .............................................................................................................. 6

2.4.6 Watercourse Monitoring Information ................................................................................ 6

2.5 BLACKPARKS PUMPING STATION .......................................................................... 6

3 REVIEW OF RECENT AVAILABLE REPORTS ................................................................. 7

3.1 SCOTTISH POWER REVIEW OF BLACKPARKS FACILITY ............................... 7

3.2 SCOTTISH POWER BLACKPARKS FACILITY REPORT (REV 2) ...................... 7

3.3 SCOTTISH WATER SOLUTIONS CASTLE DOUGLAS WASTE WATER

TREATMENT WORKS FLOOD RISK ASSESSMENT ......................................................... 8

3.4 SCOTTISH POWER GALLOWAY HYDROS CULVENNAN LAND

DRAINAGE PUMPS .................................................................................................................... 9

4 ADDITIONAL INFORMATION INPUTS ............................................................................ 10

4.1 SCOTTISH POWER ...................................................................................................... 10

4.2 DUMFRIES AND GALLOWAY COUNCIL COUNTRYSIDE RANGER .............. 10

4.3 NATIONAL TRUST FOR SCOTLAND RANGER SERVICE ................................. 10

4.4 DUMFRIES AND GALLOWAY LIBRARIES ............................................................ 10

4.5 ADDITIONAL INFORMATION .................................................................................. 10

5 FLOOD RISK ASSESSMENT ................................................................................................ 11

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TABLE OF CONTENTS

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5.1 MODEL SETUP .............................................................................................................. 11

5.2 RIVER FLOW ................................................................................................................. 14

5.3 MODEL RESULTS UNDER EXISTING GROUND CONDITIONS ....................... 15

6 DISCUSSION AND RECOMMENDATIONS ....................................................................... 17

6.1 FINDINGS UNDER EXISTING CONDITIONS ......................................................... 17

6.2 BLACKPARK PUMP FACILITY ................................................................................ 17

6.3 POSSIBLE MITIGATION MEASURES ..................................................................... 18

6.4 GENERAL CONCLUSIONS ON POSSIBLE MITIGATION MEASURES ........... 19

6.5 OUTLINE RECOMMENDATIONS ............................................................................. 19

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APPENDIX


References

Figures & Drawings

Figure 1 – Site Location

Figure 2 – Detail of Carlingwark Lane

Figure 3a – Model Cross Section Locations

Figure 3b – Model Cross Section Locations along Carlingwark Lane

Figure 4 – 1D model cross sections

Figure 5 - Detail of Model Blocked Cells

Drawing 1168-202-C01 – Survey Data supplied by the Council

Drawing 1168-202-D1 – 1 in 2year Peak Water Depths







Drawing 1168-202-D8 – 1 in 200year +GCC Peak Water Depths


Drawing 1168-202-D1 O – 1 in 2 year with Blackpark Pumps off



Drawing 1168-202-D1 MIT1












Photographs

Tables

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1 INTRODUCTION

1.1 PREAMBLE

The physical geography around Castle Douglas is generally flatter that the surrounding

hill land with the Dee valley widening considerably to the east and west. The River Dee

thus meanders through this undulating countryside and exhibits an extensive functional

flood plain.

The Carlingwark Loch has, from earliest historical times, occupied the low lying

marshland to the south of Castle Douglas. The Loch was partly drained by the

construction of the Carlingwark Lane in 1765 to facilitate the excavation and

transportation of marl for agricultural purposes.

The development of the River Dee hydro-electric scheme (the Galloway Hydros Scheme)

in the 1930s included the linking of the Loch Doon and Clatteringshaws catchments to the

River Dee system, which results in an overall increase in water flow through the Dee.

Other elements of the system provide peak rainfall attenuation leading to a reduction in

peak river flow but an overall increase in base flow. The hydro scheme therefore brought

with it an increased seasonal risk of flooding to local farmland and, as a result, a number

of small pump stations were placed in the low lying areas to the west of Castle Douglas.

These pumps, coupled with a series of flood bunds, assisted and continue to assist the

drainage of local farmland.

Notwithstanding the presence of the Blackparks Pumping Station on Carlingwark Lane

the drainage of the area around Carlingwark Loch and Castle Douglas itself remains

highly dependent on the state of the River Dee to the north and west. Raised water levels

in the Carlingwark Loch are known to occur and present a known hazard to the town of

Castle Douglas.

Dumfries and Galloway Council, in partnership with Scottish Power, is seeking to carry

out a flood risk appraisal for the town of Castle Douglas with specific reference to the risk

posed by interaction of the Carlingwalk Loch and the River Dee. Terrenus CDH Ltd was

appointed by the Council to carry out this work.

Cognisance of a number of related flood risk and flood assessment reports for the

Carlingwalk Lane watercourse and Castle Douglas has been included in the assessment

with the effect of the Blackparks Pumping Station being a key element of the study.

The Council is seeking to gather information in order to allow informed decisions to be

made regarding the future of the pumping station and the related flood defences.

First and second drafts of the report have been presented to the Council with initial

findings. This current report represents the Final report and includes comments on a

number of issues raised by the Council and by SEPA together with additional information

where necessary. This report is provided for discussion by relevant parties and will

include data and shape files in separate electronic format.

Castle Douglas

Flood Risk Assessment

For

Dumfries & Galloway Council

& Scottish Power


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1.2 OBJECTIVES OF INVESTIGATION

From the project brief and subsequent discussions with the Council the principle aims of

the assessment are to:

“enable Dumfries and Galloway Council to make an informed decision on the criticality

of the Blackparks pump station in protecting Castle Douglas from flooding events

primarily from the Carlingwark Loch and Lane and associated catchment and some

consideration of improvements to the current situation.”

The above broad objective anticipates that a review of the current situation will be carried

out as well as detailed two dimensional flood modelling of the area as a whole under a

variety of circumstances.

Information from the investigation and watercourse modelling was used to inform

possible mitigation measures relating to Carlingwark Loch and Carlingwark Lane.

1.3 REPORT STRUCTURE

The structure of this report firstly sets out the geography and hydrological environment of

the Castle Douglas area prior to considering the historical relationship of the town to the

water environment and, specifically, the Carlingwark Loch.

The detailed model of the Carlingwark Loch, Carlingwark Lane and River Dee surface

water environment is set out and the model results presented.

Finally, potential mitigation measures to reduce the risk of flooding to Castle Douglas

whilst enhancing the local environment are considered.

1.4 LIMITATIONS OF REPORT

Terrenus CDH Ltd. has prepared this report for the sole use of Dumfries & Galloway

Council and Scottish Power, in accordance with generally accepted consulting practice

and for the intended purpose as stated in the related contract agreement. No other

warranty, expressed or implied, is made as to the professional advice included in this

report.

To the best of our knowledge, information contained in this report is accurate at the date

of issue. It should be noted, however, that this report is based on the information obtained

from the sources listed in Section 2 below. There may be conditions pertaining at the site

not disclosed by these sources, which might have a bearing on the recommendations

provided if such conditions were known. We have, however, used our professional

judgement in attempting to limit this during the investigation.

It is important therefore that these implications be clearly recognised when the findings of

this study are being interpreted. In addition, this should be borne in mind if this report is

used without further confirmatory investigation after a significant delay.

The report is not, however, suitable for detailed planning and design purposes.

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2 DATA SOURCES, GEOGRAPHY & HYDROLOGICAL ENVIRONMENT

2.1 DATA SOURCES

A wide variety of data sources were consulted during the course of the investigation

including:

The Scottish Environment Protection Agency (SEPA) indicative flood risk map;

Current Topographic Maps;

Additional topographic information for Castle Douglas as provided by Dumfries and

Galloway Council;

LiDAR data procured from SEPA via Dumfries and Galloway Council comprising a

5m horizontal grid with a vertical accuracy of +/-50cm;

Aerial Photography of the Castle Douglas Area;

Geological & Hydrogeological Maps;

Scottish Power Galloway Hydros – Culvennan Land Drainage Pumps, November

2009;

Scottish Power Blackparks Facility Report (Rev 2), April 2009;

Scottish Power Review of Blackparks Facility, November 2005;

Scottish Water Solutions Castle Douglas Waste Water Treatment Works Flood Risk

Assessment, October 2008;

Dumfries and Galloway Infrastructure Engineering Guide – Project Risk

Management;

Some Stewartry Sketches, Alistair Penman 1981;

Causewayend to Castle Douglas, Alistair Penman 1986

Discussions were also held with the National Trust for Scotland Ranger service, Dumfries

and Galloway Countryside Ranger, Hydros Manager Scottish Power and SEPA offices.

A full list of references is included in the appendix to this report.

2.2 GENERAL GEOGRAPHY OF THE CASTLE DOUGLAS AREA

The valley of the River Dee in Galloway is clearly defined throughout the hills

surrounding New Galloway and in the vicinity of Loch Ken. The southern part of the

River Dee valley around Tongland is similarly topographically well defined. The physical

geography around Castle Douglas is however generally flatter and gently undulating with

the Dee valley widening considerably to the east and west.

Although the bulk of Castle Douglas is located at a higher level, the area around

Carlingwark, which is fed by the Gelston Burn from the south east, is at a similar level to

that of the wider Dee valley. At the north western periphery of Carlingwark Loch the land

rises slightly, effectively forming a low ridge that impounds flow from the south east

towards the north west and the River Dee. The Carlingwark Lane cuts through this ridge

and allows partial drainage of the Loch.

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The Carlingwark Lane watercourse also drains the Dee Marshes and agricultural grazing

land between Carlingwark Loch and the River Dee, including the outfall from the

wastewater treatment works for Castle Douglas.

The Dee Marshes are an internationally important ecological site and are registered as a:

Site of Special Scientific Interest (SSSI);

Special Protection Area (SPA); and

RAMSAR site.

The SSSI citation notes that the marshes contain areas of swamp, fen, grassland and carr

woodland and is one of the best examples of a semi-natural freshwater system in north

west Europe. The SSSI site covers an area of some 770ha.

2.3 GENERAL GEOLOGY

The superficial deposits around the existing line of the River Dee and Carlingwark Lane

are dominated by alluvium comprising Silt, Sand and Gravel of Quaternary Period origin.

To the north and east of these deposits Fluvio-glacial deposits are recorded comprising

Gravel, Sand and Silt. Around the Carlingwark Loch the superficial deposits comprise

Glacial Till.

The solid geology below the Castle Douglas area, including the Carlingwark Loch and

Carlingwark Lane, is dominated by deep marine Greywacke sedimentary rocks of the

Silurian Carghidown Formation.

2.4 HYDROLOGICAL ENVIRONMENT

2.4.1 Galloway Hydros Scheme

The River Dee catchment is a managed hydrological environment as part of the Galloway

Hydros Scheme. This hydroelectric system, built in the earlier part of the 1930’s, has a

combined catchment of over 1,300km2 in Ayrshire and Galloway and comprises eight

dams and six power stations together with associated tunnels, aqueducts and pipelines.

Loch Doon lies at the head of the scheme and is a natural loch whose level has been raised

and augmented by diverted flow from the Water of Deuch and the Bow Burn. Prior to the

hydro-scheme Loch Doon solely fed the River Doon which flows to the north. A

compensation flow continues down the River Doon however the scheme now feeds the

headwaters of the River Dee and thus the downstream power stations.

Clatteringshaws Loch is a man-made water body created by the damming of the upper

Black Water of Dee. A compensation flow is released to this watercourse with a further

piped water supply being provided for the Glenlee Power Station. Outflow from this

power station enters the River Dee upstream of Loch Ken. Overflow water from

Clatteringshaws as well as catchment run-off downstream of the loch enters Loch Ken

opposite the village of Parton.

Loch Ken is a naturally flat bottomed valley where, historically, the River Dee has spread

out to form a shallow extent of water during periods of peak flow. The hydro scheme

barrage at Glenlochar results in Loch Ken being a larger permanent body of water which

acts as a storage reservoir for the downstream Tongland Power Station. Beyond this final

power station the River Dee enters Kirkcudbright Bay and thus the wider Solway Firth.

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2.4.2 Hydrological Impact of Hydro Scheme

Since the scheme was completed local records suggest that average annual rainfall in the

Dee catchment has increased by about 20%. In addition, Loch Doon being added to the

River Dee catchment results in an overall increase in flow.

Loch Doon and Clatteringshaws Loch together with the associated catchment connectors

provide attenuation to the peak River Dee flow effectively resulting in a reduction in peak

flow but an increase in base and less extreme flows.

Reports on the impact of the Galloway Hydros Scheme on the River Dee downstream of

Loch Ken estimate that the system increases base flows by some 6m3/s on average

although this increase is highly variable due to seasonal and annual fluctuations.

Management of the hydro scheme seeks in part to reduce the risk of downstream flooding,

chiefly by restricting the flow from Loch Doon and Clatteringshaws Loch during flood

conditions. Loch Ken has a limited storage capacity and during peak flow events the

Glenlochar Barrage is opened such that the output flow from the loch is not impeded.

2.4.3 Impact of Water Framework Directive on the Hydro Scheme

The Water Framework Directive (WFD) was introduced by the European Commission in

2000 and aims to protect, improve and ensure the sustainable management of water

resources. Under the WFD a programme of measures will be implemented in a formal

River Basin Management Plan (RBMP). The Scottish Government has adopted this

directive and, therefore, the Galloway Hydros Scheme as a heavily modified water system

will seek a ‘Good Ecological Potential’ via the provision of a maximum net environmental

benefit without impacting on the operation of the scheme.

The Galloway Hydros lies chiefly within the Solway Tweed River Basin District and

partly within the Scotland River Basin District. As a result SEPA and the Environment

Agency have a joint responsibility for co-ordinating the key areas of work.

A key hydrological impact of the drive towards good ecological potential for the

Galloway Hydros is the maintenance of adequate levels of compensation flow to achieve

the ecological wellbeing of the catchment.

2.4.4 Carlingwark Lane

Carlingwark Lane drains just under 14km2 of land around Castle Douglas, including the

Gelston Burn and the output from Carlingwark Loch.

It has been suggested in the earliest maps of the area that, prior to being partly drained in

1765 by the construction of the Carlingwark Lane, the loch was at a sufficient depth to

allow drainage to the south and the Solway Firth via the Doach Burn. A review of the

local land form and available height data suggests that this was not the case and that the

Loch has always drained to the north to enter the River Dee across the wide flood plain

around Threave Island.

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In addition to the drainage of Carlingwark Loch the Lane also accepts water from a

number of local drainage channels across the lower lying ground in the vicinity (see

Figure 2). These channels are coupled with a number of bunds that prevent the free flow

of flood waters over the area during extreme storm events. These drainage bunds are

likely to be chiefly agricultural in nature and are not thought to provide any significant

protection against the flow of water during larger storm events such as the design 1 in 200

year event.

2.4.5 Carlingwark Loch

The Countryside Ranger together with local residents indicate that vegetation growth

around the upper end of the Carlingwark Lane (around Buchan Bridge) is known to

become heavy and to impede the flow of water. A number of local residents stated that

this vegetation growth has resulted in periodic raised water levels in the loch itself.

2.4.6 Watercourse Monitoring Information

SEPA runs a gauging station immediately downstream of the Glenlochar Barrage. The

data from this station is severely compromised by the function of the barrage itself, which

controls the normal flow from Loch Ken.

A total of five Scottish Power automatic water level monitors were placed by MWH from

the upstream side of Carlingwark Loch to the confluence of the Carlingwark Lane and the

River Dee. Some 30 months of data was available for three of these monitoring stations;

two of the stations were lost or compromised.

2.5 BLACKPARKS PUMPING STATION

The station is a run of river facility placed within the Carlingwark Lane, adjacent and to

the north east of Meikle Wood Hill. Scottish Power confirms that the station comprises

two sluice gates of 1.5m wide by 1.2m high, each with flap valves which prevent water

flow from the River Dee upstream towards Castle Douglas. In addition, the station

accommodates two pumps to assist the water flow from Carlingwark Loch to the River

Dee. These pumps are rated at 1.35m3/s each and are operated automatically by means of

level switches immediately up and downstream of the pumping station. The pumps are

fully automatic however the precise start up trigger levels are not known.

Potential flood waters are prevented from circumnavigating the pumping station by means

of bunds that connect the station to Meikle Wood Hill to the south and the Blackparks

Smallholdings to the north (Blackparks 3). These bunds show some sign of degradation

and no longer form a level crest height. The lowest point on the bunds is understood to be

at 44.1m OD.

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3 REVIEW OF RECENT AVAILABLE REPORTS

3.1 SCOTTISH POWER REVIEW OF BLACKPARKS FACILITY

This interim report was commissioned by Scottish Power and undertaken by The Carnie

Consultancy and MWH. The report entails consultations with a number of organisations in

the local area as well as some tenant farmers, limited topographic surveying of the area

and an assessment of the Blackparks Pumping Station.

This report suggests that the Blackparks station may have been built to allay fears of

flooding to the land downstream of the Glenlochar Barrage following the construction of

the Galloway Hydros Scheme. The report notes that the area around the Blackparks station

forms part of the Threave Estate. Within the Estate a Special Protection Area and

RAMSAR site lies downstream of the pumping station and a Site of Special Scientific

Interest covers parts of the low lying marsh land around the station.

The report states that the there is no record of the bunds on either side of the Blackparks

station being overtopped. The worst storm event record in the report is in December 1994.

The Countryside Ranger is reported to note that the level of the Carlingwark Loch

typically varies by up to 0.6m above normal level but can, on occasions, rise by up to

0.9m above normal which causes surface water drainage problems in low lying areas of

Castle Douglas.

The report concludes that the Blackparks station cannot be decommissioned but that

optimisation of the pumps could reduce running costs without presenting an additional

risk of peak water level in Carlingwark Loch.

3.2 SCOTTISH POWER BLACKPARKS FACILITY REPORT (REV 2)

This report, compiled by MWH, updates and expands the findings of the above, earlier,

report, including the installation and analysis of a number of long term water level

monitors.

The report basis was the analysis of the automatic level monitors coupled with hourly

water level data from the Glenlochar gauging station immediately downstream of the

Glenlochar Barrage. Of the five water level monitors two were lost or compromised

during the monitoring period.

The report re-iterates the earlier investigation that the Blackparks Pumping Station and

related protection bunds play an important part in the mitigation of flood risk to the lower

lying areas of Castle Douglas.

It is noted in the report that if the embankments were to breach during a flood event in the

River Dee this would inundate Carlingwark Loch.

The report make a number of recommendations with respect to the upkeep of the water

level monitoring stations and the maintenance of the flood bund associated with the

pumping station. Of the recommendations made it is understood from Scottish Power that,

to date, the flanking bunds have not been raised or maintained and that the level

monitoring points have been shut down. Scottish Power is putting into place meters that

will record the use of the Blackparks pumps in order to allow refinement of its operating

regime.

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3.3 SCOTTISH WATER SOLUTIONS CASTLE DOUGLAS WASTE WATER

TREATMENT WORKS FLOOD RISK ASSESSMENT

As part of the background preparations for the new Castle Douglas wastewater treatment

works (WWTW) Scottish Water Solutions commissioned Mouchel to carry out a flood

risk assessment.

The location of the WWTW is on the south western outskirts of Castle Douglas and,

following concerns raised by SEPA, a flood model was compiled using topographic

information from a digital terrain model (DTM) coupled with survey cross-sections

through the River Dee and Carlingwark Lane. A review within the report of the DTM

information and the topographic survey undertaken at the same time indicates a good

correlation between the two datasets.

Although the flood model includes a survey cross-section through the Blackparks

Pumping facility it appears that this represents the ground level to the east of the bund that

links the pumps to the perimeter of the functional flood plain. The height of the bund is

therefore not known and has been estimated in the model to be 45.00m OD throughout.

The flood model itself entailed a one dimensional assessment of the principal water

courses, resulting in a peak water level for a variety of potential storm event hydrographs.

The function of the Blackparks pumping station was considered within this investigation.

The report indicates the following with respect to recent local flooding;

Some historical flooding was recorded in Castle Douglas, (in the 1995-2007

period) however this was largely related to the blockage of culverts and road

gullies on the other side of the town to the WWTW (i.e. in the south east of the

town). Flood prevention activities noted were largely routine cleaning and

maintenance of culverts, culvert screens and road gullies on the other side of the

town.

…..there have been no fluvial flooding events which have affected properties in

the vicinity of the WWTW in recent years. However agricultural land close to the

Castle Douglas bypass (A75) is flooded up to approximately five times a year.

This is understood to be largely due to the operation of the barrage at

Glenlochar. During extreme rainfall events the barrage is opened to relieve

flooding upstream, resulting in flooding of farmland around Castle Douglas.

The report comments that the Glenlochar Barrage regulates flows to the Tongland Power

Station, and that, in addition, the barrage is raised to alleviate flooding downstream

following high rainfall. The barrage is however also opened if levels upstream are too

high, an action that occurs approximately 5 times a year. A recent case where the barrage

was opened due to extreme flows was in November 2006 when there was flooding in

Dalry and Galloway. At this time the flooding along the River Dee floodplain in the

vicinity of Castle Douglas was considerable but was not observed to overtop the flank

embankments associated with the Blackparks pumping station.

The report identifies that Carlingwark Loch does not drain well due to the flat lying nature

of the valley bottom and due to the water levels in the River Dee being too high to allow

free drainage. The requirement of the Blackparks station is noted to be reduced during the

Summer months indicating that some natural drainage of the Carlingwark Loch to the

River Dee may occur.

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Peak flow analysis of the River Dee and Carlingwark Lane was carried out using the

statistical procedure for the River Dee and the rainfall runoff method for the Carlingwark

Lane.

The report concludes that sizable parts of the low lying areas around the Carlingwark Lane

will be inundated during the design 1 in 200 year storm and that the Blackparks Pumping

Station would be overwhelmed during such an event.

3.4 SCOTTISH POWER GALLOWAY HYDROS CULVENNAN LAND DRAINAGE

PUMPS

The Halcrow Group was commissioned to assess the effects of the Galloway Hydros

Scheme on drainage at Culvennan Farm near the River Dee about 1km downstream of the

Glenlochar Barrage.

This investigation included an assessment of the impact of the hydro scheme on the peak

flow of the River Dee in comparison to the calculated natural flow of the watercourse.

Outputs from this study were combined with a DTM within a 1D steady state hydraulic

model in order to examine the peak water level under a variety of hydrographs for both

before and after the implementation of the hydro scheme.

This report concludes that the hydro scheme increases the average base flow of the River

Dee downstream of Loch Ken by about 6m3/s. The report does however note that the

magnitude of the base flow increase is highly variable due to seasonal and annual

fluctuations.

The flood model adopted by the report indicates that there is an increase in water level

under mean flows in the River Dee with the magnitude of increase reducing with the

increased severity of the flood event.

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4 ADDITIONAL INFORMATION INPUTS

4.1 SCOTTISH POWER

Discussions with Scottish Power were held at Glenlee Power Station. These discussions

confirmed that the pumps at Blackparks are rated at over 40 cubic feet per second and it

was concluded that each pump may be considered to have a capacity of 1.35m3/s. The

pump trigger mechanism at Blackparks is confirmed to be automatic via an electronic

level indicator. A stop alarm has been installed using the available mobile phone network

which is triggered by a pump stoppage or screen blockage. The same mechanism is used

to indicate the pump on / off periods.

4.2 DUMFRIES AND GALLOWAY COUNCIL COUNTRYSIDE RANGER

Discussions were held with the Dumfries and Galloway Council Countryside Ranger, Mr

Keith Kirk. From these discussions an additional understanding of the history of

Carlingwark Loch was reached as well as local historical information and more recent

bathymetry data for the loch.

4.3 NATIONAL TRUST FOR SCOTLAND RANGER SERVICE

Additional discussions with Mr Karl Mundey of the NTS ranger service were carried out

providing information concerning the general habitat of the Carlingwark Lane area, plant

growth along the Lane and the nature and effectiveness of the Scottish Power pumping

stations in the area.

4.4 DUMFRIES AND GALLOWAY LIBRARIES

Background historical data for the Castle Douglas areas was available from the local

library in Castle Douglas.

4.5 ADDITIONAL INFORMATION

A significant local flooding event occurred on Loch Ken in both November 2010 and

December 1978 when the level of the Loch was noted to be at the floor level of Parton

Village Hall. A recent topographic survey establishes the peak water level during these

two events to be 47.2m OD. It is understood that a similar storm event occurred in 1909

prior to the construction of the hydro scheme.

The bathymetric survey of Loch Ken carried out in 1903 suggests that a substantial part of

Loch Ken already existed at that time. This survey also suggests that the River Dee

outflow bed level from Loch Ken at Glenlochar effectively dictates the natural upstream

water level of the loch.

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5 FLOOD RISK ASSESSMENT

5.1 MODEL SETUP

General

The modelling of the River Dee/Carlingwark Lane watercourse system is relative to the

key features identified by the Council and during the site walkover, and by the review of

the available maps and surveys. For the purpose of this report particular attention is given

to the area between the confluence of the Carlingwark Lane and River Dee and the

Gelston Burn upstream of the Carlingwark Loch.

The full model of the system covers approximately 3.76km of the River Dee and about

2.1km of the Carlingwark Lane. An additional 2km of the Gelston Burn was added to the

model together with a 1.1km portion of the Threave Castle Island eastern spur. The reach

of watercourse modelled was to obtain an approximate parity with the earlier Mouchel 1D

model and established to be long enough to avoid any adverse affects on the water flow

from any significant features within the channel. Water storage upstream of the

Carlingwark Loch was also a consideration in the design of the model facilitated by an

extension to the Gelston Burn reach. The number of cross sections utilised in the model is

in relation to areas of restriction in flow and to construct a suitably representative analysis.

In this respect the cross sections mimicked those undertaken be Mouchel, using the same

topographic information. Additional cross sections were added in order to improve the

model at selected points.

For the purpose of this Flood Risk Assessment the Mike 11 software has been utilised in

conjunction with Mike21 and the MikeFLOOD software to produce a fully dynamic 2

Dimensional Model, that models the effects of flood plain storage and overland flow. As

the open channel flow software Mike11 provides the basic backbone to the model, all

cross sections within Mike11 have been adapted and incorporated in the model to provide

an accurate representation of the channel width and form. The Mike 21 entails the use of a

‘bathymetry’ file which is based on the available Digital Terrain Model (DTM) dataset. At

the point of overtopping the water in the model transfers from the Mike11 channel into the

Mike21 bathymetry where it may spread out in 2 dimensions by cell to cell transfer. The

1D and 2D integration comprises a dynamic link based on flow and momentum.

Model Survey Inputs

Topographic information obtained for the Mouchel flood model comprised a series of

cross sections through the Carlingwark Lane and River Dee and was utilised in this

assessment as discussed with the Council.

Bridges and culverts relating to the watercourses were compiled either using data from the

Mouchel report or, where applicable, by discussions with Scottish Power or measurements

undertaken by Terrenus during the site walkover inspection. Additional topographic

information was provided by the Council for the lower lying parts of Castle Douglas,

particularly the area adjacent to the Carlingwark Loch. This survey information took the

form of spot height data and was used to amend the Lidar ground surface elevations in the

‘bathymetry’ layer of the 2D model.

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Where variations in elevations were identified the grid cell was amended to conform to the

available survey information. It is noted that the variation between the survey information

and the Lidar data set in the southern part of Castle Douglas is modest and generally less

than 300mm. The topographic survey data is included in the appendix to this report.

This information was combined with the survey information and digital terrain data

obtained from SEPA via Dumfries and Galloway Council to provide as accurate an overall

representation of the river profile as possible.

The, or ground surface elevation model, was created using SEPA sourced Lidar data. This

provided height information consisting of Digital Terrain (bald Earth) Model (DTM) at

5m posting intervals. It is understood that the height data was created from the aerial

photography which was captured with a 60% overlap between frames using Photo-

Grammetric techniques. The resulting data is highly accurate when compared to other

existing datasets, typically having a vertical accuracy of +/- 50cm RMSE.

It is confirmed that the 1D element of the model is based solely on the available

topographic survey information via the Mouchel 1D model. The 2D element of the model

is based on the above DTM information as amended in the southern part of Castle

Douglas using the additional available survey information from the Council. Where

amended the DTM was adjusted to the more accurate topographic survey information and

consideration given to the impact of such adjustments on adjacent cells.

With respect to larger water bodies SEPA made the following comment:

.... conventional LiDAR pulses may not be returned from waterbodies and will

not provide suitable penetration to capture bathymetry. This means that the

accuracy of such areas is lower in comparison to dry areas. Returns from the

LiDAR sensor may be received from the water surface - giving a representation

of the water surface in the DTM. However, in many cases there may be no

returns from a water surface, leading to gaps in the dataset which are sometimes

infilled by interpolation.

The pre-storm surface water level of the key Carlingwark Loch water body was

established to be 43.5m OD using local knowledge and the detailed topographic data

throughout the low lying area of Castle Douglas. In addition the Lidar data was adapted in

certain other key areas including the loch side area of Castle Douglas and the A75 based

on the known topography and information established from the Council provided survey

data.

Additional small inflows from field drainage ditches were noted along the line of the

Carlingwark Lane. The general topography of these features was picked up as part of the

DTM data for the area.

In order to keep the model manageable yet representative of important and significant land

features (such as the A75 road embankment) a map grid of 10m was adopted for the flood

model. Minor corrections were imposed on the model where the DTM was considered to

include possible height errors.

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Downstream River Dee Boundary and initial Model Conditions

The location of the downstream boundary corresponds with the final 1D cross section on

the River Dee. In this case the boundary has been placed sufficiently far downstream to be

remote from the Carlingwark Lane and any structures in the vicinity. The downstream

boundary conditions for the site have been set in hydrodynamic mode with an open

boundary. The Hydrodynamic (HD) Module has been applied to the boundary and is

defined by the Time series (TS). The Q-h relationship at the downstream boundary is

computed using a Manning’s value of 0.045 and a slope of 0.002.

The 1D element of the model is set with an initial 0.5m water in the river channel system

prior to the commencement of the storm hydrograph.

The initial conditions for the 2D element of the model are dry at the commencement of

the storm hydrograph. The flood plain inundation is set to hydrodynamic only with a

drying depth of 0.01m and a flooding depth of 0.02m.

Structures

An important feature with all structures when modelling with MIKE11and MikeFLOOD

is that they must impose a constriction to the flow. That is, an inlet and an outlet loss must

be present over the structure and the structure’s geometry definition (with respect to flow-

area) must be smaller than both the up and downstream cross sections for all levels

defined in the structure.

Features such as the A75 embankment, the bridge over the Carlingwark Lane and the

outfall from the Carlingwark Loch via the Buchan Bridge have been picked up by the

DTM and input to the flood model.

Details of the Blackparks Pumping station, the pumping rates and associated non-return

culverts were established from previous reports, discussions with Scottish Power and the

site walk-over. The model assumes that the pumps will stop working when the peak water

level rises to 46m OD (i.e. above the existing pump bund).

River Banks and Model Domain / Active Area

The 2D active model area is shown on Figure 5 in the Appendix and extendes throughout

the lower lying flood plain area of the River Dee from north of the Glenlochar Barrage to

approximately the Lodge of Kelton downstream of Threave Island. The 2D element of the

model also includes the flood plain of the Black Bridge Burn to the west of the River Dee

and the entire Carlingwark Lane, Carlingwark Loch and Gelston Burn tributary system.

Figure 5 also indicates the blocked cells along the principal water courses (River Dee,

Gelston Burn and Carlingwark Lane), where the 1D elment of the model defines the water

flow and peak water level.

As noted above the 1D and 2D integrated model comprises a dynamic link based on flow

and momentum. This link relies on the 1D cross-sectional data to initiate flooding in the

2D element of the model and hence is based on topographic survey information provided

with the Mouchel 1D model data set.

Additional ground truthing has not been carried out for the DTM dataset however, as

noted above, the variation between the survey information in the south of Castle Douglas

and the Lidar data set is generally less than 300mm.Additional Notes

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For ease of reporting and consideration the model outputs in this report represent fixed

data from each model run. Full model outputs including shape files are presented

separately in electronic format.

The model outputs within this report, unless otherwise recorded, represent the peak water

level during related return period model design. As such the output drawings show the

extreme water levels throughout the entire storm hydrograph and not a particular moment

during the storm period. Likewise, the data provided in the model output tables represents

the peak water level at selected points.

The nominal simulation period in all model runs covers the combined Dee / Gelston peak

flood hydrographs during a 41 hour period. The computational time step for all model

runs is 4 seconds resulting in 36900 time steps for the full model run.

5.2 RIVER FLOW

Although some gauging station data is available from the Glenlochar Barrage the quality

of this data is limited by the workings of the hydro-power facilities and the station itself.

With respect to the design 1 in 200 year storm event, rainfall records and catchment

descriptors have been obtained from the Flood Estimation Handbook (FEH) with flow

rates calculated using the following methodologies.

FEH (2007) QMED (Index Flood) calculation;

Improved FEH estimate of QMED (2008);

Mean Annual Flow (MAF) using Institute of Hydrology Research paper

124 (for comparison);

Statistical analysis as provide by SEPA;

Statistical analysis as undertaken by Mouchel;

Rainfall Runoff Method as undertaken by Mouchel; and,

FEH Rainfall Runoff method.

An analysis of these methods was discussed with SEPA and the Mouchel statistical

method found to be reasonable. This resulted in a peak flow for the design storm of

495m3/s.

Peak flows for other storm events were, in agreement with the Council, adopted from the

Mouchel flood risk assessment.

A summary of the possible peak design flows for the watercourse is provided in Table 1 in

the Appendix.

The current Scottish Executive guidance ‘UKCIP02 Update (2003)’ suggests that peak

river flows may increase by between 15% and 20% in the south-west of Scotland by the

mid 2080’s due to global climate change. In line with SEPA recommendations and

following discussions with the Council an additional allowance of 20% has been added to

the peak flow over and above the estimated 1 in 200 year probability flood event. This

increase brings the peak flow for the River Dee and Carlingwark Lane to approximately

594m3/s and 43m3/s respectively.

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The catchment of the River Dee is some 810km2 to the Glenlochar Barrage and 864km2

to the Bridge of Dee. The Carlingwark Lane including the Gelston Burn adds some

13.8km2 upstream of the Bridge of Dee. The likelihood of an extreme storm occurrence

throughout the entire Dee catchment is low and, due to the differing sizes of the Dee and

Carlingwark catchments, the time to peak is likely to occur at differing times. In this

assessment separate flood hydrographs have been compiled for the Dee and Carlingwark

catchments. For the design 1 in 200 year storm event the time to peak of the Dee is about

18 hours after the commencement of the storm. For the same event the time to peak of the

Carlingwark is 12 hours after the start of the storm and hence some 6 hours prior to the

peak of the River Dee.

This variation in peak flow is considered to offer a reasonable worst case scenario for the

local area. Additional model runs were carried out to investigate the impact of differing

storm events on the Carlingwark Loch and are provided as model outputs in the appendix.

5.3 MODEL RESULTS UNDER EXISTING GROUND CONDITIONS

Using standard hydrodynamic software modelling techniques for open channel flow,

information between cross sections is interpolated through the Mike 11 software and the

river flood levels calculated accordingly. Integration of this data with Mike21 through

dynamic linkages and the MikeFLOOD software via cell to cell transfer produces a 2

Dimensional Model, which models the effects of flood plain storage and overland flow.

Uncertainties remain regarding the channel roughness that affects the relationship between

flow rate and water level. The analysis must, therefore, be regarded as approximate.

In order to fully analyse the watercourse, runs were carried out at a variety of flow

volumes as discussed below. The Manning roughness ‘n’ numbers used in the model were

in line with those adopted in the 1D Mouchel model, varying between 0.04 and 0.045 for

the watercourse channels. The flood plain was assigned a global Manning roughness

factor of 0.045. Sensitivity analysis was carried out on the 1D element of the model as

used in the 2D model where the channels were adapted to dynamic linkage. Small

variations in Manning ‘n’ value were found to have only a modest impact on the 1D

model results.

The results of the MikeFLOOD output are shown on the drawings contained within the

appendix to this report. It should be borne in mind that the actual movement of water

throughout the flood plain is affected by the timing of the storm events, a fact that is

displayed in the additional electronic submission. The drawings provided in the appendix

show peak levels around Castle Douglas for simple clarity.

The area of the Carlingwark Loch is included in the model with the radar data and a

review of both local knowledge and the detailed survey data supplied by the Council used

to provide the standing water level (43.5mOD) into which the storm hydrograph flows.

Peak water levels for the Carlingwark Loch in the vicinity of the Isle of Whitepark (in the

north of the loch) are provided in Table 3 in the appendix. Table 3 also provides details of

the various mitigation measures considered and their impacts on the Carlingwark Loch.

Under existing ground and pump operating conditions the model indicates that the

function of the upper Carlingwark Lane, Carlingwark Loch and Gelston Burn represents

poorly drained land. The level of Carlingwark Loch thus rises as the local storm event

progresses and remains high during the entire period of the Dee catchment storm period.

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These results indicate that the Blackparks Pumps represent a very small portion of the

peak flow within the Carlingwark Lane and become ineffective at any significant return

period (1 in 2 years and above). The chief effect of the pumps is therefore at the more

modest average flows within the Dee-Carlingwark system.

Notwithstanding the above it is clear that under existing ground conditions and at

relatively modest flows the pumps improve the overall drainage of the area and thus may

be seen to assist the general agricultural assets in the local area. In addition the pumps

may be seen to provide increased potential water storage of the Carlingwark Loch and

upper Gelston Burn at the commencement of a peak storm event. Nevertheless the pumps

are not seen to mitigate the overall risk of flooding during an extreme storm event.

The DTM indicates that the lower lying areas of Castle Douglas at the northern end of the

Carlingwark Loch are at between about 44m OD and 45m OD. Detailed surveying carried

out by the Council indicates that the near Loch area of the town (around Lochside Park)

the existing levels are between 43.9m OD and 44.5m OD. Ordnance Survey spot heights

and detailed survey information along Marl Street and Queen Street to the north and King

Street to the west of the Loch range between 47m OD and about 45m OD on Queen

Street. The land falls gently from these streets towards the Carlingwark Loch. Storm

events in excess of 1 in 25 years will inundate parts of the near loch area within Castle

Douglas. The risk to Queen Street and associated areas during such events will chiefly be

dependent on the initial level of the loch. It is likely that the initial loch conditions will

result in parts of the park area, loch bank and caravan park being at risk of inundation

during lesser storm events.

It should in addition be noted that the local drainage known to discharge into the

Carlingwark Loch is likely to back up during such events and that the Loch is known to

respond early in the local hydrograph.

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6 DISCUSSION AND RECOMMENDATIONS

6.1 FINDINGS UNDER EXISTING CONDITIONS

The model runs allow a number of overall conclusions to be made;

Increasing storm severity (from the 1 in 2 year event to the 1 in 200 year event)

results in a steady increase in water levels through the Carlingwark area;

The Carlingwark Loch water level rises early in the storm hydrograph and tends to

be sustained thereafter, suggesting that the constriction of the channel below the

Buchan Bridge and the very flat fall of the Carlingwark Lane itself limits outflow

from the loch at the peak of the hydrograph;

The peak water level near the Isle of Whitepark (Lochside Park) varies from

44.63m OD during the 1 in 2 year event to 44.98m OD during the 1 in 200 year

event. In reality due to possible vegetation growth around Buchan Bridge and local

storm drainage from Castle Douglas itself the latter conditions are likely to

inundate some parts and environs of Queen Street.

The impact of the Blackpark Pumps on the drainage of the Carlingwark Lane

during an extreme storm event is negligible; however the pumps do have an

impact in regulating local agricultural water levels during normal flow conditions

between the pump facilities and Castle Douglas.

6.2 BLACKPARK PUMP FACILITY

The Scottish Power report 41515757 – Rev2 dated April 2009 on the Blackparks Pumps

indicates the following:

It is clear that the Blackpark pumping station plays an essential role in allowing

a reasonably efficient discharge from Carlingwark Loch below Buchan Bridge,

and therefore alleviating the risk of inundation to the urban spread of Castle

Douglas. Equally the flank embankments that complete the Blackpark facility

must remain intact in order to alleviate the risk of inundation to the urban

spread of Castle Douglas.

The current assessment broadly agrees with the above statement concerning the flank

embankments but notes that the pumps become less significant during significant storm

events. During a more isolated storm event the pumps may result in an increased capacity

within the Carlingwark Loch system to attenuate the peak storm flow and thus reduce the

risk of flooding to Castle Douglas however such an effect is negligible in the current

model.

It is concluded that the pumps do provide an agricultural advantage in the local area (as

they were originally designed to do) but that they provide no significant mitigation to the

risk of flooding in the Castle Douglas area during the design 1 in 200 year storm event.

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6.3 POSSIBLE MITIGATION MEASURES

Following discussions with the Council consideration has been given to possible flood

mitigation measures which would reduce the risk of flooding to Castle Douglas whilst

retaining the overall aesthetic and environmental well-being of the local area. Passive

measures were preferred when considering appropriate mitigation measures.

Such measures include the following;

1. Improvement and raising of the Blackpark flank embankments (bunds) to 45.45m

OD;

2. Provision of upstream control measures on the Gelston Burn to attenuate storm

water inflow to the Carlingwark Loch thus allowing a longer period for the loch to

drain during the design storm event;

3. Provision of the Gelston Burn control measures coupled with additional

downstream control at the A75.

The location of the above possible control measures is shown on Figure 2 in the

Appendix.

The Gelston Burn control comprises a simple flap valve non-return culvert with flank

embankments at a crest level of 45.5m OD. Two differing culverts were modelled at this

location; the first being a box culvert measuring 3m width by 1m high. Such a culvert

would allow some 10m3/s to pass when full but with no upstream head. The second

culvert comprised a circular pipe 0.9m in diameter which would have a capacity of about

2.5m3/s when full with no upstream head.

The measures modelled at the A75 comprised a 5m wide by 1m high non-return gate

which did not affect the downstream water flow but did prevent flow from the River Dee

to the Carlingwark Loch. In this case the road embankment provides suitable flank

embankments.

The peak water level around the Isle of Whitepark during the model runs employing these

mitigation measures are provided in Table 3 in the Appendix.

Raising of the Blackpark Flank Embankments

It is noted that raising the flank embankments at the Blackpark Pumps results in a small

increase in peak water level in the Carlingwark Loch during the 1 in 2 year return period

and a slight decrease during the 1 in 50 year storm. It is likely that this effect is due to the

early time to concentration of the Gelston Burn catchment initially filling up the area

upstream of the pumps. Thereafter the water in this area is unable to exit due to the

increasing water levels arising from the River Dee.

Gelston Burn Control Measures

The use of the larger box culvert in the upstream Gelston Burn control does not provide

any significant attenuation of the catchment runoff and the peak water levels are found to

increase slightly in the Carlingwark Loch.

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Using a reduced culvert size significantly restricts the storm flow of the Gelston Burn and

results in the attenuation of storm water over the lower part of the Gelston Burn valley

floor. The peak water levels upstream of the control measures during the 1 in 2 year storm

are in the order of 44.79m OD rising to 45.36m OD for the 1 in 50 year event.

The impact of this attenuation is to lower the peak water level of the loch by about 110mm

during the 1 in 2 year event and raise it by some 640mm during the 1 in 50 year event.

The rise in peak water level during the 1 in 100 year event is 170mm suggesting an impact

during the more extreme storm events.

Additional A75 Control Measures

Applying control measures at the A75 allows the water immediately upstream of the A75

to drain during the early part of the storm event, however, the peak water level within the

Carlingwark Loch remains unchanged during the 1 in 2 year event when compared with

the Gelston Burn control only and shows only a modest fall during the 1 in 50 year event.

6.4 GENERAL CONCLUSIONS ON POSSIBLE MITIGATION MEASURES

The flow of water around Castle Douglas during peak storm events is complex entailing

overall poor drainage, differing times to peak flow, the presence of the Blackpark Pumps

and the variable nature of the peak flow in the River Dee due to the hydro power scheme.

Whilst the Blackpark embankments do work in tandem with the pumps themselves,

raising these features does not in itself reduce the risk of flooding at Castle Douglas.

Passive mitigation measures have been modelled but fail to provide a definitive course of

action that will reduce the risk of flooding to Castle Douglas during all storm events.

Whilst the Gelston Burn control measures do provide upstream attenuation the model

indicates that the flow from the Carlingwark Loch is restricted through the Carlingwark

Lane in the vicinity of Buchan Bridge. Such an effect is shown when comparing the

Gelston control measures with the additional A75 control where the area between the A75

and the loch drains early in the peak storm event but the loch itself does not. Any use of

the Gelston Burn for attenuation purposes would therefore have to be coupled with an

improvement of the flow of water from the loch to the area upstream of the A75.

6.5 OUTLINE RECOMMENDATIONS

The model outputs suggest that the Blackpark Pumps greatest effectiveness is on a normal

day to day basis where the water levels upstream of the pumps is kept low thus normal

field operations are maintained. Such an action formed part of the original purpose of the

pumps and should be maintained if possible, however it should be recognised that the

pumps themselves do not provide any significant flood mitigation to the Castle Douglas

area.

Passive water control and flood risk methods on the Gelston Burn and A75 could be

implemented with the existing Blackpark Pumps in place and could result in a stabilisation

of the peak level in the Carlingwark Loch should the flow of water from the loch be

improved. Additional modelling would be required to confirm this.

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oo000oo

Terrenus CDH Ltd wishes to thank Dumfries and Galloway Council and Scottish Power

for the opportunity to prepare this report. We trust that the report meets with your

requirements at this stage. However, should you wish to discuss the contents of the report

then please contact the undersigned.

Signed for and on behalf of

Terrenus CDH Ltd

W. Hume S. Curran

Director Director

CASTLE DOUGLAS


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J:\Jobs CDH\1100-1199\1168 - Dumfries & Galloway Council\1168-202 - Castle Douglas\7 - Reports\Full FINAL Appendices.doc

APPENDICES

CASTLE DOUGLAS


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J:\Jobs CDH\1100-1199\1168 - Dumfries & Galloway Council\1168-202 - Castle Douglas\7 - Reports\Full FINAL Appendices.doc

FIGURES & DRAWINGS

©Crown copyright. All rights reserved. Licence No. AL100035646

Client:


Drawing Title:

Site Location Plan

1 Orbital Court

Peel Park East Kilbride, G74 5PH

Tel: 01355 279 000 Fax: 01355 263 629

Project:

Castle Douglas


Date:

24-03-12

Figure 1 Grid Ref: NX 7470 6234

SCALE: N.T.S. DO NOT SCALE

Client:


Drawing Title:

Detail of Carlingwark Lane 1 Orbital Court

Peel Park

East Kilbride, G74 5PH

Tel: 01355 279 000 Fax: 01355 263 629

Project:

Castle Douglas Flood Risk Assessment

Date: 24-03-12

Figure 2 Grid Ref: NX 7470 6234


Blackpark Pumping Station

Blackpark Flank Bunds

River Dee

Castle Douglas

Sewerage Station

Local Drainage Channels

Possible Gelston Burn

Control Measures.

Possible A75 Control

Measures.

1 Orbital Court

Peel Park

East Kilbride

G74 5PH

Project Title

Carlingwark FRA

Project No.

1168-202

Drawing Title

Cross Sections Location

Date

20th June 2013

Dwng No.3

Figure 3a

Chainage 0

Chainage 470

Chainage 1000

Chainage 1800

Chainage 2300 Chainage 2450

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Chainage 1365

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Chainage 2236

Chainage 3760

Chainage 3455

Chainage 2875

Chainage 2497

RIVER DEE

THREAVE EAST SPUR

LOCH

Chainage 3086

Chainage 670

Client:


Drawing Title:

Carlingwark Lane Cross-Sections 1 Orbital Court

Peel Park

East Kilbride, G74 5PH

Tel: 01355 279 000 Fax: 01355 263 629

Project:

Castle Douglas Flood Risk Assessment

Date: 20-06-13

Figure 3b Grid Ref: NX 7470 6234


Chainage 0

Chainage 118.42

Chainage 261.82

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Chainage 496.12

Chainage 640.13

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Chainage 1662.04

Chainage 1846.66 Chainage 2048.23

CASTLE DOUGLAS


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DUMFRIES & GALLOWAY COUNCIL

Figure 4

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Figure 4

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3

51

8.0

8

57

5.1

4

64

6.9

7

69

5.3

6

70

3.7

4

72

5.6

9

76

7.9

7

79

9.7

1

82

1.4

8

82

8.1

6

90

2.2

1

95

3.2

9

10

18

.03

10

42

.93

11

12

.66

13

17

.84

13

88

.18

14

76

.65


0

10

20

30

40

50

60

-11

4.1

5

75

.27

9

14

4.4

45

23

6.3

54

35

1.7

95

38

7.5

67

49

3.3

99

54

7.7

28

64

3.5

15

66

4.4

34

71

1.6

37

77

0.4

2

84

6.7

28

89

3.0

21

10

67

.93

2

11

68

.80

5

12

64

.19

3

13

87

.05

14

70

.46

2

15

73

.36

3

16

35

.94

4

18

04

.78

1


0

10

20

30

40

50

60

70

-10

8.3

71

.61

14

7.6

1

22

4.5

9

32

6.6

1

42

5.1

50

1.0

8

56

9.6

1

62

3.2

8

64

6.5

4

73

1.4

8

86

2.1

5

92

6.5

4

12

44

.54

13

40

.37

15

44

.68

16

40

.02

17

29

.29

18

32

.07

19

08

.15

19

56

.94

23

38

.25


River Dee

CASTLE DOUGLAS


FOR


Figure 4

0

10

20

30

40

50

60

0

87

.02

17

2.2

9

24

9.1

9

45

8.9

6

48

7.6

2

58

9.9

6

63

6.7

71

8.5

4

79

1.1

7

82

2.1

9

92

1.4

10

18

.45

10

74

.05

11

50

.68

12

44

.13

13

43

.92

17

74

.13

19

39

.1

21

22

.99

21

64

.03

24

21

.4

25

33

.84

26

40

.05

28

25

.27


0

10

20

30

40

50

60

-24

2.2

37

-22

5.2

81

-20

8.3

24

-19

1.3

67

-17

4.4

11

-15

7.4

54

-14

0.4

98

-12

3.5

41

-10

6.5

84

-89

.62

8

-72

.67

1

-55

.71

5

-38

.75

8

-21

.80

1

-4.8

45

39

2.6

6

62

0.6

6

76

6.4

7

10

39

.35

11

37

.55

12

09

.02

14

53

.39

16

14

.95

17

60

.24

22

24

.06

27

02

.5

29

77

.7


0

10

20

30

40

50

60

0

72

.18

11

4.0

5

13

7.4

1

17

4.5

24

2.4

1

31

1.8

3

38

5.7

44

2.4

8

50

3.9

3

57

6.0

4

63

3.3

1

70

8.3

9

82

6.4

9

83

0.2

2

87

9.6

4

94

0.5

6

99

8.6

3

10

22

.8

10

57

.89

14

35

.8

15

00

.17

17

55

.98

18

12

.02


0

10

20

30

40

50

60

0

35

.06

97

.5

18

7.7

9

26

8.8

9

34

0.8

8

42

6.6

7

50

4.2

57

9.9

6

71

3.2

6

86

1.9

2

92

6.4

7

10

21

.33

10

86

.44

11

67

.14

12

45

.32

13

18

.46

13

38

.12

14

18

.87

18

23

.83

19

01

.05

20

07

.74

20

82

.92

21

63

.49


River Dee

CASTLE DOUGLAS


FOR


Figure 4

0

10

20

30

40

50

60

0

30

56

.52

91

.75

12

5.3

16

3.6

3

20

2.7

7

23

5.8

1

28

3.6

9

32

4.3

3

35

4.3

7

36

0.6

7

37

3.3

2

39

7.7

3

42

0.2

2

43

6.6

6

46

5.1

1

48

7.1

1

Cross section 3455

0

10

20

30

40

50

60

0

62

.11

13

8.2

2

22

3.7

2

27

5.9

4

32

6.9

1

38

3.1

5

47

8.2

49

5.6

9

53

6.6

3

58

2.9

4

68

0.4

8

78

8.2

87

8.5

3

96

2.1

4

10

45

.83

11

70

.25

12

55

.76

13

52

.3

14

03

.23

14

99

.42

15

66

.59

16

11

.63

16

71

.02

17

39

.15

18

08

.17

18

70

.4

Cross section 3760

River Dee

34

35

36

37

38

39

40

41

42

43

44

0 10.27 73.73 85.74 514.29 942.84 1365.48 1788.11 2236.26 2497.11 2875.51 3086.41 3455 3760

Long section

CASTLE DOUGLAS


FOR


Figure 4

0

5

10

15

20

25

30

35

40

45

50

-93

8.6

26

-85

4.1

49

-76

9.6

73

-68

5.1

97

-60

0.7

2

-51

6.2

44

-43

1.7

68

-34

7.2

91

-26

2.8

15

-17

8.3

39

-93

.86

3

-9.3

86

41

.82

4

88

.87

7

13

5.9

29

18

2.9

81

24

6.3

85

31

6.4

61

36

0.7

34

40

7.7

87

45

4.8

39

50

1.8

91

Cross section 0

0

10

20

30

40

50

60

-88

9.8

7

-82

7.5

79

-7

65

.28

8

-70

2.9

97

-6

40

.70

6

-57

8.4

15

-5

16

.12

4

-45

3.8

34

-3

91

.54

3

-32

9.2

52

-2

66

.96

1

-20

4.6

7

-14

2.3

79

-8

0.0

88

-1

7.7

97

2

7.7

79

6

6.6

7

10

5.5

6

14

4.4

51

1

83

.34

2

22

2.2

32

2

61

.12

3

31

1.6

02

3

61

.99

5

40

4.9

11

4

44

.46

4

48

3.3

55

5

22

.24

5

Cross section 350

0

10

20

30

40

50

60 Cross section 362.91

0

10

20

30

40

50

60

0

13

.79

29

.07

48

.26

61

.2

82

.28

10

4.1

1

12

4.9

9

14

4.5

7

16

5.0

2

18

3.4

8

19

1.0

5

19

3.0

9

19

6.7

6

19

8.3

20

7.1

5

21

0.9

7

22

5.6

8

24

2.3

6

25

5.1

4

26

8.7

27

8.3

4

27

9.5

2

28

7.9

8

30

6.2

8

32

5.9

7

34

6.3

4


River Dee (Threave East Spur)

CASTLE DOUGLAS


FOR


Figure 4

0

10

20

30

40

50

60

0

30

56

.52

91

.75

12

5.3

16

3.6

3

20

2.7

7

23

5.8

1

28

3.6

9

32

4.3

3

35

4.3

7

36

0.6

7

37

3.3

2

39

7.7

3

42

0.2

2

43

6.6

6

46

5.1

1

48

7.1

1


0

10

20

30

40

50

60

Cross section 1100

River Dee (Threave East Spur)

37

38

39

40

41

42

43

0 120 350 362.91 508.18 626.2 1110

Long section

CASTLE DOUGLAS


FOR


Figure 4

40

41

42

43

44

45

46

47

0 19.48 40.83 51.36 54.12 56.14 58.23 59.95 67.91 86.6 98.96

Cross section 0

0

10

20

30

40

50

60

0

6.2

13

.3

15

.7

18

.2

26

.3

27

.3

28

.3

29

.6

35

39

.5

53

71

.4

91

.9

11

0.5

12

8.9

13

8.4

15

7.4

16

2.2

16

4.6

17

6.4

20

0.3


0

10

20

30

40

50

60

0

34

.86

91

.45

10

9.4

1

18

4.1

1

22

5.3

1

28

7.9

2

36

5.3

2

45

0.0

1

53

6.7

2

61

0.8

1

68

0.6

9

74

3.4

9

76

2.8

9

76

8.7

9

82

5.4

86

4.6

3

90

6.4

94

2.3

1

97

5.8

3

10

14

.02

10

54

.14

10

84

.17

11

35

.61

11

89

.79


0

10

20

30

40

50

60

0

21

.77

68

.21

11

9.7

4

12

3.5

3

16

6.3

4

21

7.6

3

28

4.8

33

3.8

9

39

5.8

7

42

8.3

45

5.4

5

46

0.6

2

52

5.5

4

56

8.8

6

61

9.8

2

67

3.9

3

72

3.8

3

75

1.9

1


Carlingwark Lane

CASTLE DOUGLAS


FOR


Figure 4

38

40

42

44

46

48

50

0

12

5.5

6

22

5.8

3

35

8.5

2

49

1.8

6

60

3.3

3

68

6.8

4

84

3.1

6

99

9.6

5

10

92

.74

1

11

10

.26

8

11

27

.79

5

11

45

.32

1

11

62

.84

8

11

80

.37

4

11

97

.90

1

12

15

.42

7

12

32

.95

4

12

50

.48

1

12

68

.00

7

12

85

.53

4

13

03

.06

1

13

20

.58

7


0

10

20

30

40

50

60

70

0

13

3.3

9

22

5.9

7

40

9.4

3

51

0.6

8

61

4.2

6

68

6.2

1

69

6.6

57

70

6.1

65

71

5.6

73

72

5.1

82

73

4.6

9

74

4.1

99

75

3.7

07

76

3.2

16

77

2.7

24

78

2.2

32

79

1.7

41

80

1.2

49

81

0.7

57

82

0.2

66

82

9.7

74

83

9.2

83

84

8.7

91

85

8.2

99

86

7.8

08

87

7.3

16


0

10

20

30

40

50

60

-55

2

4.9

5

64

.8

11

5.5

4

16

8.2

3

23

0.9

8

27

4.6

1

31

6.5

7

36

2.2

8

40

6.4

4

30

.9

43

7.8

5

02

.48

5

44

.72

5

51

.98

6

05

.69

6

68

.44

7

04

.6

72

5.3

9

75

6.7

2

80

2.3

7

85

3.7

9

00

.54

9

47

.28

9

68

.17


0

10

20

30

40

50

60

0

12

9.6

25

6.1

38

1.3

46

9.7

59

2.9

9

68

5.9

5

73

8.8

7

84

5.0

9

93

2.5

7

10

56

.41

11

22

.68

8

11

88

.96

7

12

55

.24

5

13

21

.52

4

13

87

.80

2

14

54

.08

15

20

.35

9

15

86

.63

7

16

52

.91

6

17

19

.19

4

17

85

.47

2

18

51

.75

1

19

18

.02

9

19

84

.30

7


Carlingwark Lane

CASTLE DOUGLAS


FOR


Figure 4

0

10

20

30

40

50

60

0

13

5.3

7

28

0.5

6

39

3.8

4

48

6.0

1

55

7.1

5

69

8.2

2

82

6.5

5

91

5.9

85

96

0.5

58

10

05

.13

2

10

49

.70

5

10

94

.27

8

11

38

.85

1

11

83

.42

4

12

27

.99

7

12

72

.57

13

17

.14

3

13

61

.71

6

14

06

.28

9

14

50

.86

3

14

95

.43

6

15

40

.00

9

15

84

.58

2

16

29

.15

5


38

40

42

44

46

48

50

52


0

10

20

30

40

50

60

0

61

.7

12

9.9

19

0.1

27

4.6

35

1.1

41

4.2

48

0

55

2.0

2

56

6.1

1

57

5.0

6

59

2.1

5

67

0.9

2

73

0.0

1

81

2.5

8

89

1.5

8

97

1.5

10

42

.57


0

10

20

30

40

50

60


Carlingwark Lane

CASTLE DOUGLAS


FOR


Figure 4

0

10

20

30

40

50

60


0

10

20

30

40

50

60

70

-72

10

2.2

5

12

0.5

2

22

7.7

8

36

3.0

8

47

9.5

5

60

1.7

1

66

6.5

9

71

1.7

83

75

6.9

75

80

2.1

68

84

7.3

6

89

2.5

53

93

7.7

45

98

2.9

37

10

28

.13

10

73

.32

2

11

18

.51

5

11

63

.70

7

12

08

.9

12

54

.09

2

12

99

.28

4

13

44

.47

7


0

10

20

30

40

50

60

70

-48

97

.38

1

14

0.0

4

22

9.0

88

34

6.8

15

46

3.3

7

58

7.8

67

67

8.6

76

72

3.7

12

76

8.7

48

81

3.7

85

85

8.9

87

90

4.6

35

95

0.2

83

99

5.9

31

10

41

.57

9

10

87

.22

6

11

32

.87

3

11

78

.52

2

12

24

.16

9

12

69

.81

8

13

15

.46

5

13

61

.11

3

14

06

.76


0

10

20

30

40

50

60

-24

10

4.8

81

15

2.8

47

22

4.9

94

32

6.6

1

44

3.0

29

54

5.6

56

66

2.1

17

71

8.7

31

76

2.7

37

80

2.1

2

84

7.2

59

88

5.6

79

93

0.9

96

97

0.2

01

10

14

.38

6

10

54

.72

4

10

97

.77

6

11

39

.24

5

11

81

.16

6

12

23

.76

8

12

64

.55

5

13

08

.29

1

13

47

.94

5

13

92

.81

3

14

31

.33

5


Carlingwark Lane

CASTLE DOUGLAS


FOR


Figure 4

Carlingwark Lane

41.4

41.6

41.8

42

42.2

42.4

42.6

42.8

43

43.2

0 118.42 261.82 415.03 496.12 640.13 897.17 983.95 1056.04 1215.12 1420.97 1644.16 1662.04 1846.66 1913.85 1981.04 2048.23

Long section

0

10

20

30

40

50

60

0

93

.41

16

5.0

8

19

7.1

9

28

8

40

9.7

3

52

9.4

8

64

7.6

5

73

6.1

17

78

2.0

52

82

7.9

87

87

3.9

21

91

9.8

56

96

5.7

91

10

11

.72

5

10

57

.66

11

03

.59

4

11

49

.52

9

11

95

.46

4

12

41

.39

9

12

87

.33

3

13

33

.26

8

13

79

.20

2

14

25

.13

7

14

71

.07

2


1 Orbital Court

Peel Park

East Kilbride

G74 5PH

Project Title

Carlingwark FRA

Project No.

1168-202

Drawing Title

Existing Pump-On 2yr

Date

20th June 2013

Dwng No.

1168-202-D1

Peak Water Level 43.63m OD

1 Orbital Court

Peel Park

East Kilbride

G74 5PH

Project Title

Carlingwark FRA

Project No.

1168-202

Drawing Title


Date

20th June 2013

Dwng No.

1168-202-D2


1 Orbital Court

Peel Park

East Kilbride

G74 5PH

Project Title

Carlingwark FRA

Project No.

1168-202

Drawing Title


Date

20th June 2013

Dwng No.

1168-202-D3


1 Orbital Court

Peel Park

East Kilbride

G74 5PH

Project Title

Carlingwark FRA

Project No.

1168-202

Drawing Title


Date

20th June 2013

Dwng No.

1168-202-D4


1 Orbital Court

Peel Park

East Kilbride

G74 5PH

Project Title

Carlingwark FRA

Project No.

1168-202

Drawing Title


Date

20th June 2013

Dwng No.

1168-202-D5


1 Orbital Court

Peel Park

East Kilbride

G74 5PH

Project Title

Carlingwark FRA

Project No.

1168-202

Drawing Title


Date

20th June 2013

Dwng No.

1168-202-D6


1 Orbital Court

Peel Park

East Kilbride

G74 5PH

Project Title

Carlingwark FRA

Project No.

1168-202

Drawing Title

Exisitng Pump-On 200yr

Date

20th June 2013

Dwng No.

1168-202-D7


1 Orbital Court

Peel Park

East Kilbride

G74 5PH

Project Title

Carlingwark FRA

Project No.

1168-202

Drawing Title

Exisitng Pump-On 200yr+GCC

Date

20th

June 2013

Dwng No.

1168-202-D8


1 Orbital Court

Peel Park

East Kilbride

G74 5PH

Project Title

Carlingwark FRA

Project No.

1168-202

Drawing Title

Exisitng Pump-On 1000yr

Date

20th June 2013

Dwng No.

1168-202-D9


1 Orbital Court

Peel Park

East Kilbride

G74 5PH

Project Title

Carlingwark FRA

Project No.

1168-202

Drawing Title

Pump Off 2yr

Date

20th June 2013

Dwng No.

1168-202-D1 O


1 Orbital Court

Peel Park

East Kilbride

G74 5PH

Project Title

Carlingwark FRA

Project No.

1168-202

Drawing Title

Pump-Off 50yr

Date

20th June 2013

Dwng No.

1168-202-D5 O


1 Orbital Court

Peel Park

East Kilbride

G74 5PH

Project Title

Carlingwark FRA

Project No.

1168-202

Drawing Title

Pump-Off 200yr

Date

20th June 2013

Dwng No.

1168-202-D7 O


1 Orbital Court

Peel Park

East Kilbride

G74 5PH

Project Title

Carlingwark FRA

Project No.

1168-202

Drawing Title

MIT1 2yr

Date

20th June 2013

Dwng No.

1168-202-D1MIT1


1 Orbital Court

Peel Park

East Kilbride

G74 5PH

Project Title

Carlingwark FRA

Project No.

1168-202

Drawing Title

MIT2 2yr

Date

20th June 2013

Dwng No.

1168-202-D1MIT2


1 Orbital Court

Peel Park

East Kilbride

G74 5PH

Project Title

Carlingwark FRA

Project No.

1168-202

Drawing Title

MIT3 2yr

Date

20th

June 2013

Dwng No.

1168-202-D1MIT3


1 Orbital Court

Peel Park

East Kilbride

G74 5PH

Project Title

Carlingwark FRA

Project No.

1168-202

Drawing Title

MIT4 2yr

Date

20th

June 2013

Dwng No.

1168-202-D1MIT4


1 Orbital Court

Peel Park

East Kilbride

G74 5PH

Project Title

Carlingwark FRA

Project No.

1168-202

Drawing Title

MIT1 10yr

Date

20th June 2013

Dwng No.

1168-202-D3MIT1


1 Orbital Court

Peel Park

East Kilbride

G74 5PH

Project Title

Carlingwark FRA

Project No.

1168-202

Drawing Title

MIT1 50yr

Date

20th June 2013

Dwng No.

1168-202-D5MIT1


1 Orbital Court

Peel Park

East Kilbride

G74 5PH

Project Title

Carlingwark FRA

Project No.

1168-202

Drawing Title

MIT2 50yr

Date

20th June 2013

Dwng No.

1168-202-D5MIT2


1 Orbital Court

Peel Park

East Kilbride

G74 5PH

Project Title

Carlingwark FRA

Project No.

1168-202

Drawing Title

MIT3 50yr

Date

20th

June 2013

Dwng No.

1168-202-D5MIT3


1 Orbital Court

Peel Park

East Kilbride

G74 5PH

Project Title

Carlingwark FRA

Project No.

1168-202

Drawing Title

MIT4 50yr

Date

20th June 2013

Dwng No.

1168-202-D5MIT4


1 Orbital Court

Peel Park

East Kilbride

G74 5PH

Project Title

Carlingwark FRA

Project No.

1168-202

Drawing Title

MIT3 100yr

Date

20th June 2013

Dwng No.

1168-202-D6MIT3


1 Orbital Court

Peel Park

East Kilbride

G74 5PH

Project Title

Carlingwark FRA

Project No.

1168-202

Drawing Title

MIT4 100yr

Date

20th

June 2013

Dwng No.

1168-202-D6MIT4


CASTLE DOUGLAS


FOR


J:\Jobs CDH\1100-1199\1168 - Dumfries & Galloway Council\1168-202 - Castle Douglas\7 - Reports\1168-202 Castle Douglas FRA FINAL Rev

1.doc

PHOTOGRAPHS

CASTLE DOUGLAS

FLOOD RISK ASSESSSMENT

FOR


Plate 1 – View from upstream end of Gelston Burn looking north west.

Plate 2 – View of upper Gelston Burn looking south east.

CASTLE DOUGLAS


FOR


Plate 3 – View of Carlingwark Loch looking north west.

Plate 4 –

Plate 4 – View of shore area around Carlingwark Loch near Isle of Whitepark.

CASTLE DOUGLAS


FOR


Plate 5 – Looking south towards Carlingwark House. Note new sewage treatment facility on left.

Plate 6 – Carlingwark Lane looking north east from the A75 road bridge.

CASTLE DOUGLAS


FOR


Plate 7 – Looking north west towards the Blackparks Pumps from the A75 bridge.

Plate 8 – Upstream side of the Blackparks pump station.

CASTLE DOUGLAS


FOR


Plate 9 – View of low lying ground on the downstream side of the Blackparks Pump station.

Plate 10 – Looking south west from Blackpark Smallholdings towards the pump station.

CASTLE DOUGLAS


FOR


Plate 11 – Looking north from Meikle Wood Hill towards Threave Castle.

Plate 12 – From Meikle Wood Hill looking north east with the Blackparks Pump station in the middle distance.

CASTLE DOUGLAS


FOR


Plate 13 – Downstream side of Blackparks Pump station (pumps currently in action).

CASTLE DOUGLAS


FOR


Plate 14 – Upper part of Carlingwark Lane showing constricting channel growth.

Plate 7 –

Plate 15 – View of upstream side of A75 road bridge.

CASTLE DOUGLAS


FOR


Plate 17 – View of non-return culvert gates at Blackparks Pump station.

Plate 16 – View of Carlingwark Lane from pump station looking downstream

CASTLE DOUGLAS


FOR


Plate 18 – Looking south from the pump station.

Plate 19 – View of upstream side of pump station.

CASTLE DOUGLAS


FOR


Plate 20 – Carlingwark Lane looking towards the A75 bridge.

Plate 21 – Carlingwark Loch and the Buchan Bridge outfall.

CASTLE DOUGLAS


FOR


Plate 23 – Constriction downstream of Buchan Bridge.

Plate 22 – View below Buchan Bridge.

CASTLE DOUGLAS


FOR


Plate 24 – Excavated section of Carlingwark Lane downstream of

Buchan Bridge.

CASTLE DOUGLAS


FOR


J:\Jobs CDH\1100-1199\1168 - Dumfries & Galloway Council\1168-202 - Castle Douglas\7 - Reports\1168-202 Castle Douglas FRA FINAL Rev

1.doc

TABLES

FEH QMED (using

2007 methodology)

combined with

Growth curve

FEH QMED (using

2008 methodology)

combined with

Growth curve

IHR 124

Rural

(Catchments

<25km2)

Rainfall

Runoff

Methodology

(MIKE)

SEPA

Statistical

Analysis

Mouchel

2008 report -

Statistical

Method

Mouchel 2008

report - Rainfall

Runoff Method

Adopted

Peak Flow

200 year 779 886 n/a 1401 541 495 n/a 495

200 year plus potential Global

Climate Change (GCC) of 20% 935 1063 n/a 1681 649 594 n/a 594

200 year 777 902 n/a 1417 n/a 528 n/a 528


Climate Change (GCC) of 20% 932 1082 n/a n/a 634 n/a 634

200 year 13 18 29 86 36 n/a 36 36


Climate Change (GCC) of 20% 15 21 34 103 43 n/a 44 43

Note: FEH CD-ROM 3 Dataset used

River Dee at

Bridge of Weir

Carlingwark

Lane at Castle

Douglas

Table 1 - Summary of Peak 1 in 200yr Flow Rates

All flow volumes are expressed in m3/s

River Dee at

Glenlochar

Job No: 1168-202

2 year 5 year 10 year 25 year 50 year 100 year 200 year

200 year plus

potential Global

Climate Change

(GCC) of 20% 1000 year

River Dee at Glenlochar 238 301 341 391 247 461 495 594 1938

Carlingwark Lane at Castle Douglas 11 15 18 23 27 32 36 43 53

Table 2 - Summary of Peak Flow Rates for a Variety of Return Periods All flow volumes are expressed in m3/s

Job Number 1168-202

Blackparks Pump On

throughout storm event.

Blackparks Pump Off

(failed or switched off). MIT 1 MIT 2 MIT 3 MIT 4

2 Year 43.63 43.63 43.66 43.64 43.52 43.52

5 Year 43.78

10 Year 43.88 43.92

25 Year 44.06

50 Year 44.37 44.37 44.43 44.36 45.01 44.94

100 Year 44.76 45.09 44.93

200 Year 44.98 44.92 44.97

200 Year plus GCC 45.25

1000 Year 45.86

Explanatory Notes: All levels are expressed in relation to OD,

Pre Storm Carlingwark Loch Water Level of 43.5m

Blackparks bund at about 45.00m OD

Exsisting Conditons Freeflow of water throughout system except at Blackparks with one way gate culverts and twin automatic pumps

MIT 1 Repair of Blackparks bund to 45.45mOD, Blackparks pumps off, Gill Burn control with weir at 45.5mOD and culvert with capacity of about 10m3/s

MIT 2 Repair of Blackparks bund to 45.45mOD, Blackparks pumps off

MIT 3 Repair of Blackparks bund to 45.45mOD, Blackparks pumps off, Gill Burn control with weir at 45.5mOD and culvert with capacity of about 2.5m3/s

MIT 4 Repair of Blackparks bund to 45.45mOD, Blackparks pumps off, Gill Burn control with weir at 45.5mOD and culvert with capacity of about 2.5m3/s, A75 one way gate.

Job Number 1168-202

Table 3 - Peak Water Levels around Isle of Whitepark

Existing Conditions Mitigation Measures

castle douglas flood risk assessment - dumgal

Documents