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South Eastern CFRAM Study HA15 Hydraulics Report - DRAFTFINAL
IBE0601Rp0015 F02
DOCUMENT CONTROL SHEET
Client OPW
Project Title South Eastern CFRAM Study
Document Title IBE0601Rp0015_HA15Hydraulics Report
Model Name Ballyroan
Rev.
Status Author(s) Modeller Reviewed by Approved By Office of Origin Issue Date
D01 Draft T. Carberry L. Howe I Bentley G, Glasgow Belfast 21/02/2014
D02 Draft T. Carberry L.Howe M. Brian G.Glasgow Belfast 12/06/2014
F01 Draft Final
T. Carberry R.Clements
L.Howe K.Smart G.Glasgow Belfast 25.11.2014
F01 Draft Final
T. Carberry R.Clements
L.Howe K.Smart G.Glasgow Belfast 13/08/2015
South Eastern CFRAM
Study
HA15 Hydraulics Report
Ballyroan Model
South Eastern CFRAM Study HA15 Hydraulics Report –DRAFT FINAL
IBE0601Rp0015 F02
Table of Reference Reports
Report Issue Date Report Reference Relevant Section
South Eastern CFRAM Study Flood Risk Review
November 2011
IBE0601 Rp0001_Flood Risk Review_F01 3.4.1
South Eastern CFRAM Study Inception Report UoM15
July 2012 IBE0601Rp0008_HA 15 Inception Report_F02
4.3.2
South Eastern CFRAM Study Hydrology Report UoM15
October 2013
IBE0601Rp0010_HA15_Hydrology Report_F01
4.2
South Eastern CFRAM Study HA11-17 SC4 Survey Contract Report
January 2014
IBE0601Rp0016_South Eastern CFRAMS Survey Contract Report_F01
1.8
4 Hydraulic Model Details ................................................................................................................... 1
4.2 Ballyroan model ....................................................................................................................... 1
4.2.1 General Hydraulic Model Information .............................................................................. 1
4.2.2 Hydraulic Model Schematisation ..................................................................................... 2
4.2.3 Hydraulic Model Construction .......................................................................................... 9
4.2.4 Sensitivity Analysis ........................................................................................................ 16
4.2.5 Hydraulic Model Calibration and Verification ................................................................. 16
4.2.6 Hydraulic Model Assumptions, Limitations and Handover Notes .................................. 18
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4 HYDRAULIC MODEL DETAILS
4.2 BALLYROAN MODEL
4.2.1 General Hydraulic Model Information
(1) Introduction:
The South Eastern CFRAM Study Flood Risk Review report (IBE0601 Rp0001_Flood Risk Review_F01)
highlighted Ballyroan as an AFA forfluvialflooding based on a review of historic flooding and the extents of
flood risk determined during the PFRA.
The Ballyroan AFA is located on the Gloreen Stream, a tributary of the River Nore.The Ballyroan AFA is
affected by both the Gloreen Stream and its tributary the Crubeen Stream.The Gloreen Stream is split into
the ‘Gloreen’ Stream and ‘Gloreen A’Stream in the model extent. The Gloreen Stream passes through the
AFA and flows southwest, where it joins part way along the Gloreen A Stream at 2,300m chainage (as
shown in Error! Reference source not found.). The Gloreen A Stream then continues southwest for
approximately 5km and discharges into the River Nore. A survey of the Gloreen reach shows that the
Gloreen A reach, at its upstream extent (0m chainage), was originally linked to the Gloreen reach.
However, no connection exists at this location now, and there is no hydraulic interaction between the two.
Three gauging stations are located on the modelled reaches; however, there are no flow or level
dataavailable for these stations.The total contributing catchment area at the downstream end of the model
is 39.4km2, with approximately 15km
2 of this area entering the model above Ballyroan. This includes the
Crubeen Stream, an HPW tributary of the Gloreen Stream, which flows through Ballyroan from Cullenagh
Mountain. Downstream of the AFA, a number of small tributaries join the Gloreen Stream before it enters
the River Nore.
All watercourses are modelled using the MIKE suite of software. The Gloreen Stream, and its tributary the
Crubeen Stream, are modelled as 1D-2D to the confluence with the Gloreen A Stream. These
watercourses are designated as entirely high priority due to them being located in the AFA.Gloreen A
Stream is modelled as 1D-2Dfrom its upstream extent down tothe Mounteagle Road Bridge, this is due to
its close proximity to the AFA. The downstream extent of the Gloreen A Stream from the Mounteagle Road
Bridge is modelled as 1D only; this part of the channel is designated as entirely medium priority.
Input from Model 1 (Ballyragget) at the downstream extent of Model 2 (Ballyroan) is not considered, as the
Ballyroan AFA is more than 6 km upstream of the downstream boundary. Refer to Section 4.2.3 of this
report for upstream and downstream model interaction
(2) Model Reference: HA15_BALL2
(3) AFAs included in the model: Ballyroan
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(4) Primary Watercourses / Water Bodies (including local names):
Reach IDName
15GLOR Gloreen Stream
15CRUB Crubeen Stream
15GLORAGloreen A Stream
(5) Software Type (and version):
(a) 1D Domain:
MIKE 11 (2011)
(b) 2D Domain:
MIKE 21 – Rectangular Mesh
(2011)
(c) Other model elements:
MIKE FLOOD (2011)
4.2.2 Hydraulic Model Schematisation
(1) Map of Model Extents:
Figure 4.2.1 and 4.2.2 illustrate the extent of the modelled catchment, river centre line, HEP locations and
AFA extents as applicable. The Gloreen catchment contains three Upstream Limit HEPs, one Downstream
Limit HEP, two Intermediate HEPs and one Tributary HEP which is modelled. The Gloreen catchment
contains three Gauging Stations but no Gauging Station HEPs as flow data is unavailable.
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Figure 4.2. 1 Map of Model Extents
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Figure 4.2. 2 Map of Model Extents at the AFA
(2) x-y Coordinates of River (Upstream extent):
Table 4.2.1Watercourses included in the model
Reach ID River Name x y
15GLOR Gloreen Stream 247052.0 187673.5
15CRUB Crubeen Stream 247792.4 188838.6
15GLORA Gloreen A Stream 244638.2 189404.5
(3) Total Modelled Watercourse Length: 14.6 km (approx.)
(4) 1D Domain only Watercourse Length: 5.0 km
(approx.)
(5) 1D-2D Domain
Watercourse Length:
10.0 km
(approx.)
(6) 2D Domain Mesh Type / Resolution / Area: Rectangular / 5 metres / 13.5 km2
The DTM has been adjusted to account for key features. Details of this have been included in Section
3.3.2 of this report. Bridge and road deck levels are occasionally not picked up in raw LiDAR data and so
they have been represented in the 2D domain by adjusting the z levels of grid cells at their locations. The
deck levels are based on topographic survey data.
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(7) 2D Domain Model Extent:
Figure 4.2.3 illustrates the modelled extents and the general topography of the catchment.
Figure 4.2. 3 2D Model Extent
Figure 4.2.4 shows an overview drawing of the model schematisation. Figure4.2.5 and Figure 4.2.6 show
detailed views. The overview diagram covers the model extents, showing the surveyed cross-section
locations, AFA boundary and river centreline. It also shows the area covered by the 2D model domain.
The detailed areas are provided where there is the most significant risk of flooding. These diagrams
include the surveyed cross-section locations, AFA boundary and river centreline. They also show the
location of the critical structures, as discussed in Section 4.2.3(1), along with the location and extent of the
links between the 1D and 2D models.
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Figure 4.2. 4 Model Schematic Overview
Figure 4.2. 5 Model Schematic (A)
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Figure 4.2. 6 Model Schematic (B)
(8) Survey Information
(a) Survey Folder Structure:
First Level Folder Second Level Folder Third Level Folder
CCS_S15_M02_15CRUB_WP2_Finals_13
0118
Where: Ballyroan
CCS - Surveyor Name
S15 – South Eastern CFRAM Study Area,
Hydrometric Area 15
M02 - Model Number 02
15CRUB - River Reference
WP2 - Work Package 2
130118 - Date issued (18 Jan 2013)
Data Files
Drawings
GIS Files
Photos (Naming
convention is in the
format of Cross-Section
ID and orientation -
upstream, downstream,
left bank or right bank)
(b) Survey Folder References:
Reach IDName File Ref.
15GLORGloreen A Stream CCS_S15_M02_15GLOR_A_WP2_Finals_130118
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15 GLOR Gloreen B Stream
15CRUB Crubeen Stream
(9) Survey Issues:
(a) 15CRUB00038 (Access track culvert at 247100E 188400N) in Figure 4.2.7 was not surveyed as
surveyors advised that they would flood out easily and did not warrant surveying due to
As such no further actions were required.
(b) 15GLOR00741 (A=access track culvert at 24
advised that they would flood out easily and did not warrant surveying due to
further actions were required. The structure is located approximately 400m upstream of the u
boundary of Gloreen A. A map is included in Figure 4.2.8 to show the
Figure 4.2. 715CRUB00038 (Access track)
Figure 4.2. 815GLOR00741 (Access track)
(c) A query was raised as to whether there is a connecting channel between Gloreen and Gloreen A
HA15 Hydraulics Report
4.2-8
Gloreen B Stream CCS_S15_M02_15GLOR_B_WP2
CCS_S15_M02_15CRUB_WP2_
(a) 15CRUB00038 (Access track culvert at 247100E 188400N) in Figure 4.2.7 was not surveyed as
advised that they would flood out easily and did not warrant surveying due to
As such no further actions were required.
ccess track culvert at 244900E 189502N) was not surveyed as
ld flood out easily and did not warrant surveying due to the rural location. As such no
The structure is located approximately 400m upstream of the u
map is included in Figure 4.2.8 to show the location of the structure (red circle).
15CRUB00038 (Access track)
15GLOR00741 (Access track)
) A query was raised as to whether there is a connecting channel between Gloreen and Gloreen A
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15GLOR_B_WP2_Finals_130118
_Finals_130118
(a) 15CRUB00038 (Access track culvert at 247100E 188400N) in Figure 4.2.7 was not surveyed as the
advised that they would flood out easily and did not warrant surveying due to the rural location.
N) was not surveyed as the surveyors
rural location. As such no
The structure is located approximately 400m upstream of the upstream
location of the structure (red circle).
) A query was raised as to whether there is a connecting channel between Gloreen and Gloreen A
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Streams. CCS Surveyors confirmed that there is no longer a connecting channel between the two
reaches, see Figure 4.2.9. There is a dry ditch present but no water flows between these reaches any
more. As there is no critical flow path remaining, no survey was required.
Figure 4.2. 9Gloreen & Gloreen A Stream former connecting channel
No processing of the bathymetry was carried out.
4.2.3 Hydraulic Model Construction
(1) 1D Structures (in-channel along
modelled watercourses):
See Appendix A.1
Number of Bridges and Culverts: 15
Number of Weirs: 0
The survey information recorded includes a photograph of each structure, which has been used to
determine the Manning's n value. Further details are included in Chapter 3.5.1. A discussion on the way
structures have been modelled is included in Chapter 3.3.4.
Critical structures:
15GLOR01047D – Main Street Bridge
Culvert capacity is insufficient during the higher return periods (1% and 0.1% AEP). This leads to localised
flooding within the AFA. Flooding during the 1% AEP return period is limited to immediately upstream of
the bridge and does not affect any properties in the AFA. During the 0.1% AEP event, flood extents widen
affecting several properties.
Gloreen A
Gloreen
Former connecting channel
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Figure 4.2. 10Main Street Bridge Culvert (15GLOR01047D)
15GLOR0670E – Mounteagle Road Bridge
Culvert capacity is insufficient to convey flood flows during the simulated return periods 10%, 1% and
0.1% AEP. Flood waters are held back and exceed the channel capacity innundating local agricultural
areas. The flood extents widen with the more extreme return periods (1% and 0.1% AEP). No properties
are affected by the flooding.
Figure 4.2. 11Mounteagle Road Bridge Culvert (15GLOR0670E)
15GLOR00404D – Portlaoise Road Bridge (N77)
Bridge capacity is insufficient to convey flood flows during all return periods (10%, 1% and 0.1% AEP).
Floodwaters back up and exceed channel capacity on both banks.
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Figure 4.2. 12 Portlaoise Road Bridge N77 (15GLOR00404D)
15GLOR00108D – Blackhill/Tullyroe Road Bridge
Bridge structure is insufficient to convey flood flows during all return periods (10%, 1% and 0.1% AEP).
This results in elevated water level upstream of the bridge, flood waters inundate both banks, but extent is
wider on left bank. Flood extent widens with more extreme events (1% and 0.1% AEP), water depths
increase significantly from the 1% to the 0.1% AEP return period.
Figure 4.2. 13 Blackhill/Tullyroe Road Bridge (15GLOR00108D)
(2) 1D Structures in the 2D domain
(beyond the modelled watercourses):
None
(3) 2D Model structures: None
(4) Defences:
Type Watercourse Bank Model Start
Chainage(approx.)
Model End
Chainage (approx.)
None
(5) Model Boundaries - Inflows:
Full details of the flow estimates are provided in the Hydrology Report (IBE0601Rp0010_HA15 Hydrology
Report_F01 - Section 4.2 and Appendix D). The boundary conditions implemented in the model are
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shown below:
Figure 4.2. 14MIKE 11 Boundary Information
The time-to-peak of inflow hydrographs generated during the hydrological analysis have been reviewed
during the calibration process.In addition to this, Laois County Council drainage engineers advised that
land upstream of Main Street in the AFA (see Section 4.2.6.3) should flood more frequently. Modelled
flows were less than those estimated
timings werereviewed so thepeaks
validate the model. The updated flows now match the estimated flows
discussed in Appendix A.3.
Figure 4.2. 15Upstream Inflow (HEP 15_12_1)
The upstream boundary of the Gloreen catchment is located at HEP 15_12_1
location is 15GLOR01162D. A point inflow was therefore applied at this node to account for flow entering
the Gloreen River upstream of this location.
HA15 Hydraulics Report
4.2-12
MIKE 11 Boundary Information
peak of inflow hydrographs generated during the hydrological analysis have been reviewed
In addition to this, Laois County Council drainage engineers advised that
land upstream of Main Street in the AFA (see Section 4.2.6.3) should flood more frequently. Modelled
flows were less than those estimated at the HEP check locations. As such, the inflow hydrograph peak
peaks coincide. This was done to ensure a worst
. The updated flows now match the estimated flows at the downstream boundary
Upstream Inflow (HEP 15_12_1)
Gloreen catchment is located at HEP 15_12_1, the model node ID at this
point inflow was therefore applied at this node to account for flow entering
River upstream of this location.The figure above shows the upstream HEP 15_12_1 input, for
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peak of inflow hydrographs generated during the hydrological analysis have been reviewed
In addition to this, Laois County Council drainage engineers advised that the
land upstream of Main Street in the AFA (see Section 4.2.6.3) should flood more frequently. Modelled
he inflow hydrograph peak
as done to ensure a worst–case scenario and to
at the downstream boundary as
, the model node ID at this
point inflow was therefore applied at this node to account for flow entering
figure above shows the upstream HEP 15_12_1 input, for
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the 0.1% AEP return period.
(6) Model Boundaries –
Downstream Conditions:
The downstream boundary condition is a Q-h relationship, generated
based on the cross-section at the downstream extent of the model.
This is located just upstream of the confluence of the Gloreen A Stream
(Ch 7816.52) and the River Nore.Joint probability with Model 1
(Ballyragget) has not been considered and a Q-h boundary has been
applied at the downstream extent. The Ballyroan AFA is greater than 6km
upstream of the downstream boundary of the model. Therefore backwater
from Model 1 (Ballyragget) is considered to have no affect on flood flows
within the AFA. The Q-h boundary is to be assessed during sensitivity
analysis. Please refer to Section 6.3.1 of the Hydrology Report and
Section 3.6.1 of this report for the approach.
(7) Model Roughness:
(a) In-Bank (1D Domain) Minimum 'n' value: 0.030 Maximum 'n' value: 0.050
(b) MPW Out-of-Bank (1D) Minimum 'n' value: 0.030 Maximum 'n' value: 0.070
(c) MPW/HPW Out-of-Bank
(2D)
Minimum 'n' value: 0.034
(Inverse of Manning's 'M')
Maximum 'n' value: 0.059
(Inverse of Manning's 'M')
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Figure 4.2. 16 Map of 2D Roughness (Manning's n)
This map illustrates the roughness values applied within the 2D domain of the model. Roughness in the
2D domain was applied based on land type areas defined in the Corine Land Cover Map with
representative roughness values associated with each of the land cover classes in the dataset.
(d) Examples of In-Bank Roughness Coefficients
Crubeen Stream - 15CRUB00002 Gloreen Stream - 15GLOR0896
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Figure 4.2. 17 15CRUB00002 Roughness
Manning’s n = 0.050
Clean, winding stream, trees and heavy brush
along banks (submerged at high water levels)
Figure 4.2. 18 15GLOR0896 Roughness
Manning’s n = 0.045
Clean, winding stream, brush along banks
(submerged at high water level)
Gloreen A Stream - 15GLOR00281
Figure4.2. 19 15GLOR00281 Roughness
Manning’s n = 0.045
Clean, winding stream, brush along banks
(submerged at high water level)
Gloreen A Stream – 15GLOR0034
Figure 4.2. 20 15GLOR0034 Roughness
Manning’s n = 0.040
Clean, winding stream, some brush along banks
(submerged at high water level)
Gloreen Stream - 15GLOR1078 Crubeen Stream - 15CRUB00062I
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Figure 4.2. 21 15GLOR1078 Roughness
Manning’s n = 0.035
Standard natural stream or river in stable condition
Figure 4.2. 22 15CRUB00062I Roughness
Manning’s n = 0.03
Concrete lined channel
4.2.4 Sensitivity Analysis
Sensitivity analysis to be reported in Final Version of report (F02), as agreed with OPW.
4.2.5 Hydraulic Model Calibration and Verification
(1) Key Historical Floods (fromIBE0600Rp0008_HA15 Inception Report_F02 unless otherwise
specified):
(a) Nov 2013 Laois County Council Drainage Engineers advisedat a workshop of draft flood
mapping on 13th November 2013 that flooding previously affected Chapel Road within
the AFA, and that the floodwaters originated from the Crubeen Stream. The model
results do not show any flooding of Chapel Road. The 1% AEP water level is well
below top of bank along this stretch (as shown in Appendix A.2). Since the Crubeen
Stream is small and heavily channelized it may be susceptible to blockage. It is
therefore considered that this flooding may have been caused by a blockage in the
Crubeen Stream channel. Blockage analysis will be carried out during sensitivity
analysis and discussed in Final Version of report (F02).
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Figure 4.2. 23 0.1% AEP flood extent near Chapel Street
(b) Jan 1995 Taken from the County Laois Strategic Flood Risk Assessment – Table 5-1 Historical
flood eventreports: ‘Major flooding is reported in the Portaloise area. Flooding also
reported in Ballyroan, Stradbally, Mountmellick, Mountrath, Portarlington, Durrow,
Timahoe and Rosenallis’.
No further information is available for this event. Flooding is shown to occur in
Ballyroan during all modelled events (10%, 1% and 0.1% AEP).
Summary of Calibration
Very little historical data relating to flooding in the Ballyroan AFA is available. Therefore, quantifying
historical flood events is difficult as there is no data available for the hydrometric gauges within the model
extents.
There are no significant model instabilities. There are minor fluctuations in the discharge (<0.5m3/s) during
the 1% and 0.1% AEP events where large quantities of flow exchange over the lateral links between
approximately 3,000m and 4,800m chainage (see Section 4.2.6.2). This does not affect the model results
and the model is considered to be performing satisfactorily. The mass balance of the model is -1.54%, as
such the model is considered fit for purpose.
Model flows were checked against the estimated flows at HEP check points where possible to ensure they
were within an acceptable range. During the lower severity event 10% AEP, the modelled flows matched
well (within 5%, or within 0.5m3/s) with the estimated flows. During the more extreme events, large
quantities of flow leaves the channel due to lack of capacity in the channel causing lower than estimated
modelled flows in the middle reach of the model. However, at the downstream extent of the model the
modelled flows are within 5% of the estimated flows suggesting the model is well anchored to the
hydrological estimates.
Overall, as there is very little data available and as the return period of historical events is very uncertain,
the model should be described as poorly calibrate. However, despite lack of calibration and verification
data, it is considered to be performing satisfactorily for design event simulation and matches well to
Chapel St
Crubeen Stream
Gloreen Stream
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estimated flows.
(2) Public Consultation Comments and Response:
To be completed for final version of the report (F02)
(3) Standard of Protection of Existing Formal Defences:
Defence
Reference
Type Watercourse Bank Modelled Standard
of Protection (AEP)
None
(4) Gauging Stations:
There are three gauging stations within the model extents:
(a)Ballydine Bridge (15028)No flow or water level data is available for this gauging station and it has
therefore not been used to calibrate the model.
(b)Ballyroan (15032)No flow or water level data is available for this gauging station and it has therefore
not been used to calibrate the model.
(c)Tonduff (15054)No flow or water level data is available for this gauging station and it has therefore not
been used to calibrate the model.
(5) Other Information:
Although there are no recorded historical flood events in Ballyroan, discussions with Laois County Council
Drainage Engineers highlightedthat areas downstream of the AFA (in the proximity of the Gloreen and
Gloreen A confluence, and upstream of the confluence) were not shown to flood as often as they
should.However, this flooding is over 5km upstream of the River Nore and so is not caused by high flows
in the Nore River.
4.2.6 Hydraulic Model Assumptions, Limitations and Handover Notes
(1) Hydraulic Model Assumptions:
(a) The in-channel and structureroughness coefficients initially selected based on normal bounds were
reviewed during the calibration process. It is considered that the selected values are representativeof the
channel and surrounding floodplain.
(b) The time-to-peak of inflow hydrographs generated during the hydrological analysis have been
reviewed during the calibration process. The inflow hydrograph peak timings for all watercourses have
been adjusted to coincide as the modelled peak flows were less than those estimated. This was validated
by the comments received during consultation with Local Authority staff who advised that modelled results
did not show flooding occurring as often as it should.Flood hydrographs are statistical estimates based on
catchment descriptors; occasionally the modelled peak flows do not coincide in the main channel.
Adjusting the hydrograph timings so peaks coincide is justifiable as it ensures a worst case scenario
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forflooding in the AFA.
(c) For design run simulations it has been assumed that all culverts and screens are free of debris and
sediment.
(2) Hydraulic Model Limitations and Parameters:
(a) No gauging stations are available to provide flow/stage calibration.
(b) Where only the upstream/downstream face of a structure has been surveyed, the surveyed face has
been duplicated and used as the opposite face of the structure. This is considered acceptable as all these
structures were of short length and so there should be minimal difference between the upstream and
downstream orifice of each structure.
(c) Grid cell size is 5m. Features smaller than 5m wide, such as walls or flow paths, may not be accounted
for within the 2D domain. This may be less accurate in urban areas. The Gloreen and Gloreen A
watercourses are represented in the LiDAR (prior to watercourse blockout in MIKE FLOOD). As such, it is
assumed that any depression in the terrain where the former flow path between the Gloreen A and
Gloreen Stream was located, would also be represented if present.
(d) A large portion of the model is medium priority watercourse, 1D-only,providing less detail than the high
priortity 1D-2D portion of the model.Where glass walling was an issue in the MPW,
cross-sections have been extended using NDHM data allowing for wider flood extents and more accurate
water levels than the surveyed sections.
(e) All culverts with only the upstream or downstream face surveyed had the upstream invert level raised
by 0.02m to improve model stability.
Hydraulic Model Parameters:
MIKE 11
Timestep (seconds) 2
Wave Approximation High Order Fully Dynamic
Delta 0.85
MIKE 21
Timestep (seconds) 2
Drying / Flooding depths (metres) 0.02 / 0.03
Eddy Viscosity (and type) 0.25 (Flux Based)
MIKE FLOOD
Link Exponential Smoothing Factor
(where non-default value used)
River Gloreen, Ch 3080.17 - Ch 4159.72: 0.8;
River Gloreen A, Ch 364.264 – Ch 1091.73: 0.8;
River Gloreen A, Ch 2318.9 – Ch 2516.68: 0.8;
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River Gloreen A, Ch 2530.03 – Ch 2790.0: 0.8.
Lateral Length Depth Tolerance (m)
(where non-default value used)
All default
(3) Design Event Runs & Hydraulic Model Handover Notes:
This model is influenced by fluvial sources only. The 10%, 1% and 0.1% AEP events were simulated.
There is little flooding within the AFA extent itself, but some localised flooding does occur. The only
significant flooding in the AFA during all return periods (10%, 1% and 0.1% AEP) is caused by the Main
Street culvert.A lack of capacity in the Main Street culvert, diverting flow in Gloreen A Stream, causes
localised flooding of grassland in the Ballyroan AFA during higher return periods (0.1% AEP) (Figure
4.2.24Error! Reference source not found.). The lack of capacity of the structure causes flood waters to
back up, inundating the area upstream of the bridge.
Figure 4.2. 24 0.1% AEP flood extent in the Ballyroan AFA
The section of Gloreen A Stream passing through Ballyroan town is heavily channelised. This section is
found to have sufficient capacity for high return periods (10% and 1% AEP). However, during the more
extreme return periods (0.1% AEP), flooding occurs in the AFA. This results from a combination of
insufficient channel capacity and water backing up, upstream of the Main Street Bridge.
The capacity of the Crubeen Stream was found to be adequate during all events simulated
(10%, 1% and 0.1% AEP).
Downstream of the Ballyroan AFA there is large amount of out-of-bank flooding, this is due to a lack of
capacity in the Gloreen A Stream and the Gloreen Stream during high return periods
(1% and 0.1% AEP). No properties are affected.
The Mounteagle Road bridge is a critical structure. During all return periods simulated
(10%, 1% and 0.1% AEP), the bridge restricts flow and increases water levels upstream, resulting in
flooding of limited extent upstream of the bridge.
Main Street Bridge
(15GLOR01047D)
AFA Extent
(Red Line)
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Figure 4.2. 25 0.1% AEP return period downstream of the Ballyroan AFA
Downstream of the AFA, the Gloreen Stream is directed under an N77 Road Bridge on Portlaiose Road
(15GLOR00404D). This bridge is insufficient to convey flood flows. This results in backing up of water and
localised flooding during all return periods (10%, 1% and 0.1% AEP). The backwater effect from this
bridge has a direct impact on flooding at the bridge location approximately 100m upstream
(15GLOR00417D), which causes increased water levels upstream as a result of water backing up from
15GLOR00404D. Local agricultural land is affected but no properties are affected by this flooding.
Figure 4.2. 26 Flood extent in the Gloreen Stream at the Portlaoise Rd (N77) Bridge
Downstream of the Portlaoise Road (N77) Bridge to the Ballydine Bridge (R430), the Gloreen Stream has
sufficient capacity to convey the 10% AEP return period. During the more extreme return periods
(1% and 0.1% AEP), the Gloreen Stream has insufficient capacity to convey flood flows. This results in
some flooding on the left bank, downstream of the Portloaise Road Bridge, and significant flooding on the
right bank along this reach. Local agricultural land is affected, but no properties are affected by this
0.1% AEP
Flood Extent
Mounteagle Road Bridge
(15GLOR00670E)
0.1% AEP Flood Extent
Unknown Rd Bridge
(15GLOR00417D)
Portlaoise (N77) Rd Bridge
(15GLOR00404D)
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flooding.
Figure 4.2. 27 Flood extent in the Gloreen Stream between the Portloaise Rd (N77) Bridge and the Ballydine (R430) Bridge during the 0.1% AEP return period
From the Ballydine Road Bridge (N77) to the Gloreen Bridge (15GLOR00108D), the Gloreen Stream has
insufficient capacity to convey flood flows during all return periods (10%, 1% and 0.1% AEP). Floodwaters
inundate both banks along this reach. The area is largely agricultural and no properties are affected by this
flooding.
The Gloreen Bridge (15GLOR00108D) is a critical structure which causes flooding during all return periods
(10%, 1% and 0.1% AEP). The bridge structure is insufficient to convey flood flows, resulting in elevated
water levels upstream of the bridge, which exceed channel capacity and overtop both banks, flooding
affects local agricultural land and no properties.
Downstream of the Gloreen Bridge, the Gloreen Stream has insufficient capacity to convey flood flows
during all return periods. Floodwaters exceed channel capacity and inundate both banks. Left bank
flooding extends from the Gloreen Bridge, approximately 200 m downstream. Flooding on the right bank
extends from the Gloreen Bridge to the downstream extent of the Gloreen Stream at its confluence with
the River Nore.
Ballydine Bridge
(15GLOR000245D)
0.1% AEP
Flood Extent
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Figure 4.2. 28 0.1% AEP flood extent in the Gloreen Stream, from the Gloreen Bridge to its confluence with the River Nore
As noted in the survey queries in Section 4.2.2(9),the Gloreen A Stream and the Gloreen Stream used to
be connected. The lack of capacity of the Gloreen Stream at this location causes localised flooding during
all modelled return periods.
(4) Hydraulic Model Deliverables:
Please see Appendix A.4 for a list of all model files provided with this report.
(5) Quality Assurance:
Model Constructed by:
Model Reviewed by:
Model Approved by:
Laura Howe
Malcolm Brian
Grace Glasgow
Gloreen Bridge
(15GLOR00108D)
0.1% AEP
Flood Extent
River Nore
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APPENDIX A.1
MODELLED STRUCTURES
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Structure Details – Bridges & Culverts
RIVER BRANCH
CHAINAGE ID LENGTH (m)
OPENING SHAPE
HEIGHT (m)
WIDTH (m)
SPRING HEIGHT FROM INVERT (m)
MANNING’S N
Bridges
CRUBEEN 300 15CRUB00105I 212.28 CIRCULAR 1.20 1.20 - 0.015
CRUBEEN 547 15CRUB00078D 11.4 CROSS-SECTION DB 2.58 1.94 1.63 0.045
CRUBEEN 730 15CRUB00062I 40.07 CROSS-SECTION DB 0.80 1.79 - 0.03
GLOREEN A 2123 15GLOR00568D 8.3 CIRCULAR 1.00 1.00 - 0.015
GLOREEN A 2523.5 15GLOR00525D 5.35 CROSS-SECTION DB 2.49 3.06 1.50 0.04
GLOREEN A 3647 15GLOR00417D 3.74 CROSS-SECTION DB 1.74 3.23 - 0.045
GLOREEN A 3794 15GLOR00404D 22.2 CROSS-SECTION DB 2.14 3.87 - 0.045
GLOREEN A 5365 15GLOR00245D 9.19 LW-TABLE 2.51 4.87 1.30 0.035
GLOREEN A 6747 15GLOR00108D 1 6.55 LW-TABLE 2.57 2.69 0.99 0.035
GLOREEN 1204 15GLOR01047D 9.43 CROSS-SECTION DB 2.04 3.14 0.78 0.04
GLOREEN 1843.5 15GLOR00980E 4.53 CROSS-SECTION DB 1.37 3.15 - 0.035
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Structure Details – Bridges & Culverts
RIVER BRANCH
CHAINAGE ID LENGTH (m)
OPENING SHAPE
HEIGHT (m)
WIDTH (m)
SPRING HEIGHT FROM INVERT (m)
MANNING’S N
Bridges
GLOREEN 4833.5 15GLOR00670E 4.83 CROSS-SECTION DB 1.80 2.10 0.92 0.04
GLOREEN 1633.5 15GLOR01000E 4.58 CROSS-SECTION DB 1.67 3.11 - 0.04
GLOREEN A 1098 15GLOR00667E 8.1 CIRCULAR 1 1 - 0.015
GLOREEN A 6747 15GLOR00108D 2 6.55 LW-TABLE 2.53 2.77 0.74 0.035
All weirs in the Network file are overtopping weirs which form part of a composite structure with the culvert / bridge at the corresponding
chainage.
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APPENDIX A.2
RIVER LONG SECTION PROFILES
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Crubeen River 1% AEP Peak Water Levels
HA15 Hydraulics Report
4.2-28
Crubeen River 1% AEP Peak Water Levels
Hydraulics Report – DRAFT FINAL
F02
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APPENDIX A.3
ESTIMATED PEAK FLOW AND MODEL FLOW
COMPARISON
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IBE0601 SE CFRAM STUDY RPS
PEAK WATER FLOWS
AFA Name BALLYROAN
Model Code HA15_BALL2
Status DRAFT
Date extracted from model 01/04/2014
Peak Water Flows River Name & Chainage AEP Check Flow (m3/s) Model Flow (m3/s) Diff (%) GLOREEN A 2321.96
15_378_6_Inter_RPS
10% 7.21 6.98 3.19
1% 12.78 9.36 26.76
0.1% 21.88 12.94 40.87
GLOREEN A 7794.07
15_1938_5_RPS
10% 8.64 8.99 4.02
1% 15.00 15.22 1.44
0.1% 25.21 26.02 3.20
GLOREEN 3683.75 10% 5.39 5.81 7.68
15_281_4_Inter_RPS 1% 9.88 6.05 38.77
0.1% 17.44 6.14 64.82
CRUBEEN 1327.1 10% 1.10 1.11 0.97
15_467_5 1% 2.02 2.03 0.22
0.1% 3.59 3.58 0.24
The table above provides details of flow in the model at every HEP inflow, check point, modelled
tributary and gauging station.
The difference between modelled peak flows and estimated flows in the Crubeen River at chainage
1327.1is less than 1%during all return periods simulated (10%, 1% and 0.1% AEP). As such the
modelled peak flows in this river are well anchored to the estimates.
The modelled peak flows in the Gloreen A River at chainage 7794.07 are within 5% of the estimated
peak flows during all return periods simulated (10%, 1% and 0.1% AEP). As such the modelled peak
flows in this river are well anchored to the estimates.
The modelled peak flow in the Gloreen A River at chainage 2321.96 is within 5 % of the estimated
peak flow during the 10% AEP return period. During the more extreme return periods
(1% and 0.1% AEP), modelled peak flow is between 36-40% lower than the estimates. During the 1%
and 0.1% AEP return periods, the Gloreen A River has insufficient capacity to convey flood flows as
such large quantities of flow exceed channel capacity and flow overland away from the the HEP
location.
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The modelled peak flow in the Gloreen River chainage 3683.75 is 7% higher when compared with the
estimated peak flow during the 10% AEP return period. This difference is less than 0.5m3/s and
caused by a lesser degree of hydraulic attenuation than is captured in the design flow estimations.
During the more extreme return periods (1% and 0.1% AEP), the flows in the Gloreen River chainage
3683.75 are between 38-64% lower when compared with the estimated peak flows. During the 1% and
0.1% AEP return periods, channel capacity upstream of the HEP is insufficient to convey flows. Water
flows north, away from the HEP location. This attenuation is higher than captured in design
estimations and accounts for the lower than estimated peak flows.
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APPENDIX A.4
DELIVERABLE MODEL AND GIS FILES
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Model Files
Fluvial Model Files
MIKE FLOOD MIKE 21 MIKE 21 – DFS2 FILE MIKE 21 RESULTS
HA15_BALL2 _MF_DES_Q10_7 HA15_BALL2_M21_DES_Q10_7 HA15_BALL2_DFS2_Rec_DES_Mesh_2 HA15_BALL2_M21_DES_Q10_7
HA15_ BALL2 _MF_DES_Q100_7 HA15_BALL2_M21_DES_Q100_7 HA15_BALL2_M21_DES_Q100_7 HA15_ BALL2 _MF_DES_Q1000_7 HA15_BALL2_M21_DES_Q1000_7 HA15_BALL2_M21_DES_Q1000_7
MIKE 11 - SIM FILE & RESULTS FILE MIKE 11 - NETWORK FILE MIKE 11 - CROSS-SECTION FILE MIKE 11 - BOUNDARY FILE
HA15_BALL2_M11_DES_Q10_7 HA15_BALL2_NWK_DES_7 HA15_BALL2_XNS_DES_7 HA15_BALL2_BND_DES_Q10_7
HA15_BALL2_M11_DES_Q100_7 HA15_BALL2_BND_DES_Q100_7 HA15_BALL2_M11_DES_Q1000_7
HA15_BALL2_BND_DES_Q1000_7
MIKE 11 - DFS0 FILE MIKE 11 - HD FILE & RESULTS FILE
HA15_BALL2_TS_Q10_edit
HA15_BALL2_HD_DES_Q10_7
HA15_BALL2_TS_Q100_edit HA15_BALL2_HD_DES_Q100_7 HA15_BALL2_TS_Q1000_edit HA15_BALL2_HD_DES_Q1000_7
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GIS Deliverables - Hazard
Flood Extent Files (Shapefiles) Flood Depth Files (Raster) Water Level and Flows (Shapefiles)
Fluvial Fluvial Fluvial
O05EXFCD001C0 o15dpfcd001c0 O05NDFCDC0
O05EXFCD010C0 o15dpfcd010c0
O05EXFCD100C0 o15dpfcd100c0
Flood Zone Files (Shapefiles) Flood Velocity Files (Raster) Flood Defence Files (Shapefiles)
To be issued with Final version of this report Defended Areas O05ZNA_FCDC0 NA O05ZNB_FCDC0 Defence Failure Extent NA