…the morphology and sediment transport of alpine rivers have been strongly altered during the last...

HyMoCARES case studiesmonitoring of

hydromorphological restoration projects in alpine

rivers

coordinated byFrédéric Liébault (Irstea Grenoble)

www.alpine-space.eu/hymocares

www.facebook.com/HyMoCARES

HyMoCARES Final conference Bolzano-Bozen, October 2, 2019

The morphology and sediment transport of alpine rivers have been strongly altered during the last 70 years

• Gravel mining

• Hydropower

• Flood protection works

• Erosion-control works in mountains

• Global changes (climate and land-use)



Lech River (LFV)

Stramentizzo dam (PAT)Gravel pit in the Durance (@B.Terrier)

Hydrogeomorphic responses to human pressures have been particularly strong in the Alpine Space

• Channel incision and narrowing

• Rapid shifting of emblematic alpine channel patterns (e.g. braiding, and anastomosing)

• Channel clogging with fine sediments



1952 2015

Arve River (IGN)

Channel incision in soft bedrock, Salzach 1969 (BAW-IWB)

1950s braided channel

Drôme (Irstea)

www.alpine-space.eu/projects/hymocares/en/homewww.alpine-space.eu/about/links-downloads/interreg

Alterations of alpine river hydromorphology have consequences on ecosystem services

• Loss of aquatic and terrestrial habitats

• Loss of biodiversity

• Effect on water quality (biochemical cycling)

• Groundwater table lowering

• Instability of infrastructures



Bridge collapse, Drôme (Irstea)

Belletti et al., 2013 Hydrobiologia

http://www.alpine-space.eu/projects/hymocares/en/home

http://www.alpine-space.eu/about/links-downloads/interreg


Hydromorphological restoration: an effective management strategy for the recovery of heterogeneity and variability?

• Sediment replenishment• Riverbed widening• Bank protection removal• Dam/weir removal• E-flow increase• Recreation of macroforms• Remeandering



Buëch (EDF)

Drau (BOKU)

Talvera (APC-PAB)



HyMoCARES restoration/management projects

13 pilot sites in the Alpine Space (Austria, France, Germany, Italy, Slovenia, Switzerland)



• Sediment replenishment (Buëch, Drac)

• Riverbed widening (Adige, Drac, Drau, Isarco, Lech, Mur, Talvera, Wertach)

• Bank protection removal(Adige, Drau, Isarco, Lech, Mur, Salzach, Wertach)

• Weir removal/opening (Talvera)

• E-flow increase in project (Drava, Maggia, Lech)


Monitoring activities• Topographic surveys (remote sensing)• Sediment transport monitoring• Fish surveys• Macroinvertebrate surveys• Water temperature



SfM orthomosaic, Drau (BOKU)

Tracer stones, Drau (BOKU)

UAV survey (Irstea)

Bathymetric survey, Isarco (PAB)

Electric fishing, Isarco (PAB)

dGPS survey (Irstea)




Key messages from HyMoCARES monitoring activities





Fluvial remote sensing data now offer powerful tool to monitor physical effects of stream restoration projects, providing high-resolution data covering large spatial scales (airborne LiDAR, UAV-SfM surveys, thermal infra-red imagery, RFID sediment tracing)



Talvera DoD from bathymetric LiDAR surveys(APC-PAB)

Thermal infrared imagery, Drac (@B. Marteau CNRS/CD05)

Bedload tracing experiments of HyMoCARES highlight rapid bedload transfer rates in Alpine rivers (several km per years). This implies relatively short residence time of gravels in restored reaches, but also a strong sediment connectivity with upstream sediment sources.



Bedload tracing in the Drau (BOKU)May-August 2017


Sediment replenishment is a successful solution to stop channel incision or to recreate braided morphology in highly altered alpine gravel bed rivers (Drac and Buëch case studies)



gravel wave

Active channel elevation change downstream of the St Sauveur dam

Brousse et al., 2019

Front of the gravel wave of the Buëch (Irstea)

Spontaneous recovery of braidingDrac (@SIGosphere)



Bed widening is a successful solution to improve morphological conditions and subsequent habitat heterogeneity of large embanked alpine rivers, provided that the sediment supply is high (Drau, Wertach)



Wertach (LFV)

Drau (BOKU)


Ecological effects of hydromorphological restoration are still difficult to demonstrate using data from monitoring programs, even if some trends reveal positive effects on fish populations or macroinvertebrates communities

Much more ambitious monitoring programs exploring longer spatial and temporal scales are needed to statistically isolate restoration effects from other forcings/controls and to go beyond case study applications (e.g. MBACI and EPT designs)



Adapted from Roni et al., 2013



Long-term physical and ecological effects of restoration projects are still highly uncertain (mainly due to the natural variability of sediment supply and hydrological regimes, and to the long term recovery processes), and it is of crucial importance to pursue monitoring efforts in the future



Evolution of the proportion of fast-flowing flow fish species


Focus on HyMoCARES restoration projects





Highlights of the main results

Case studies in South Tyrol:Talvera, Isarco and Adige Rivers

Autonomous Province of Bolzano (ITA)

EURAC, Bolzano 02.10.2019

Civil Protection Agency - PAB -

in partnership with Mountain-eering S.r.l.

Dott. Ing. Silvia Simoni

Dott.ssa Francesca Minute

Dott. Daniel Spitale

Dott. Ing. Michele Portogallo





Case studies: Talvera, Isarco, Adige

02.10.2019

Bolzano



Case studies: restored reaches

Bolzano

02.10.2019



Case studies: main measures

02.10.20191

TALVERA: weir and check

dam removal/opening

ISARCO: flow deflectors and

bank wall reinforcementADIGE: lateral connectivity

and riverbank re-shaping



TALVERA – Weir removal enhanced grain size variability

(well sorted distribution)

11.06.2019

T2: in 2019 a coarser grain size distribution was observed compared to the 2013 analysis, due to the recent check dam removal

T4: no major changes between 2013 and 2019 were observed due to the recent check dam removal (sediments need time to move downstream)



ISARCO – DoD results

11.06.201916

Flow deflectors:

- conveying the flow towards the middle of the channel

- avoiding riverbank erosion and providing embankment stability

- slow flow areas are suitable to new habitats development



ADIGE – Positive impact on fish population

11.06.2019

Thymallus thymallus

Trout species

restored reach

Lana

Postal

Bolzano

Adige River

Thymallus thymallus

Results of the

Electrofishing:

ADIGE: lateral connectivity and riverbank re-shaping


Case studies in France:Drac and Buëch

Irstea Grenoble and CD05


National Research Institute of Science and Technology for Environment and Agriculture, Grenoble

Conseil Départemental des Hautes-Alpes, Gap

In collaboration with

Univ. Paris Diderot

EVS UMR5600-CNRS Lyon

MRE






Two highly altered gravel-bed braided rivers in the Southern French Alps: Buëch and Upper-Drac

• Accelerated incision of the Upper Drac under the effect of intensive gravel mining (cutting through lacustrine clay deposits)

• Strong incision of the Buëch River downstream of the St Sauveur dam (associated with the stabilization of the braided pattern)

• In both cases, local effects of human pressures have been likely amplified by a general context of sediment supply decrease from the catchment (reforestation, end of Little Ice Age)










Active channel narrowing and incision of the Upper Drac










Active channel narrowing of the Buëch (1956-2006)

St Sauveur dam built in 1990-1991





Two ambitious gravel replenishment operations

40 000 m3 of gravel replenishment downstream of the St Sauveur dam in 2016 (EDF) to stop channel incision



Two ambitious gravel replenishment operations

355 000 m3 of coarse sediment used to recreate a braided channel along the Upper Drac (2013-2014, CLEDA)



Morphological effects of gravel replenishment

• Sediment replenishment in the Buëch effectively stop channel incision by generating a 40-cm deep gravel wave with a front stopping at 2.3 km from the dam after a 5-yr flood

• 52% of the artificial berms eroded during the 5-yr flood (good efficiency of the replenishment design)

• A spontaneous recovery of braided morphology is observed along the Upper Drac, through the self-formation of anabranches

• Bedload tracing confirms sediment continuity between the restored reach of the Drac and its first upstream sediment source (Chabottes braided plain) at the yearly scale

LiDAR DEM differencing of the Buëch after the November 2016 flood (Brousse et al., 2019 RRA)



Morphological effects of gravel replenishment

• Sediment replenishment in the Buëch effectively stop channel incision by generating a 40-cm deep gravel wave with a front stopping at 2.3 km from the dam after a 5-yr flood

• 52% of the artificial berms eroded during the 5-yr flood (good efficiency of the replenishment design)

• A spontaneous recovery of braided morphology is observed along the Upper Drac, through the self-formation of anabranches

• Bedload tracing confirms sediment continuity between the restored reach of the Drac and its first upstream sediment source (Chabottes braided plain) at the yearly scale

Bedload tracing in the Drac(Brousse PhD)

Spontaneous recovery of the braided channel in 2018 (SIGosphere UAV photo)



Ecological effects of gravel replenishment (biological communities)

• Drac: improvement of the biological quality indicators after restoration (but difficult to isolate restoration effects from improved wastewater treatment in upper catchment)

• Drac: spectacular increase of brown trout population in the restored reach (effect of restoration or fish pass deployment?)

• Buëch: differences in biological quality between restored and control sites are dominated by the dam effect (no clear effects of the gravel replenishment on the ecological quality)

4,2

9,9

3,8

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DRAC0070 (upper) DRAC0080 (restoration area) DRAC0090 (lower)

Dif

fere

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Invertebrate richness

IBG

Indicator Group

Brown trout in the Drac (restored reach)


Case studies in Austria:Drau and Mur

BOKU, BAW-IWB


University of Natural Resources and Life Sciences, Vienna

Federal Agency for Water Management



Einleitung

Case study site Salzach River

390

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vati

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lateral distance (m)

2005 xs 504

2015 xs 504

The HyMoCARES channel evolution diagram

Bed widened and slight lift of bed level

Initiation of bank erosion downstream ofnew ramp to compensate bedload deficit

Case study site Upper Drau River

Longterm morphologicalmonitoring

October 2001June 2002September 2002June 2003June 2004July 2005July 2006July 2007September 2008September 2009May 2011May 2018July 2019

Sediment consumption duringthe development of a morenatural morphology

Case study site Upper Drau

Reinitiation of morphodynamics whenmorphological constraints change due tofurther widening actions and floods(October 2018 flood)

Case study site Upper Drau

Further bedwidening in 2014

Massive downstream effectduring October2018 flood

Bank protection destroyedduring October 2018 flood– Reinitiation ofmorphodynamics

Magnitude of bank erosionremained below expectations

Case study site Mura River

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Profil 1

2007 2018

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Profil 2

2007 2018

Temporary stop/reversal of bedincision

Continued threat of riverbedbreakthrough – testing of erodibilityof fine-grained tertiary sedimentbelow gravel bed

Case study site Mura River

Jet-Test

τc ≥ 130 N m-2

no fluvial erosion

1. Highly unstable onceit is transported!

2. Abrasion due tobedload transport?


Case studies in Slovenia:Drava River

IzVRS


Institute for Water of the Republic of Slovenia, Ljubljana



Drava River pilot area in Slovenia

Pilot area present ecosystem services

• Hydropower,

• Habitat related services,

• Retention of nutrients,

• Cultivated crops,

• Surface and groundwater for drinking and non-drinking purposes,

• Flood risk mitigation,

• Aesthetics of landscape,

• Water-related activities.

Monitoring activities:

• Suspended sediment monitoring,

• Bank erosion measurements



Monitoring campaign:

suspended sediment measurements• Three groups of monitoring campaigns were conducted to obtain

data of suspended sediment concentration in relation to constant

(environmental) flow in winter, summer and in case of an extreme

hydrological event;

Winter E-flow Summer E-flow Extreme hydrological event

(30. 10. – 2. 11. 2018)



Bank erosion measurements (in cooperation with/executed by BOKU Vienna)

• Estimating bank retreat and interaction with the depositing sediment supplied from

upstream

• Two tests – borehole shear test to estimate cohesion shear strength (bank geotechnical

stability) and jet test to estimate erosion rate dependence on shear stress (bank fluvial

erodibility)

y = 0.738x + 15.5R² = 0.9976

0

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sh

ea

r s

tre

ng

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Result Comparison

Langendoen

Jet

test

Borehole

shear test

Bank geotechnical

stability rate on

shear strength

Bank fluvial erodibility rate



Results of monitoring campaigns• Results of three monitoring campaigns measuring suspended sediment concentration served as

key input data to establish sediment transport model,

• Sediment transport model was used as a (recognized) WPT2 tool to assess the effect of restoration action on hydromorphology (Zlatoličje bank stabilization with groynes) and to provide base for developing habitat model as another WPT2 tool to assess restoration action (E-flow amendment) effect on habitats (adult Danube salmon as a representative species)

Max deposition 4 vs 8 groynes

Max erosion 4 vs 8 groynes

Normalized preference curves

Habitat suitability vs

Q (SI>0,75)




Case studies in Germany:Lech River

FVB-IGB and LFV


Leibniz Institute for Freshwater Ecology and Inland Fisheries, Berlin

Bavarian Fishery Association



Case study at Lech river• Planning of an artificial oxbow• Installation of spawning grounds for

danube salmon• Sediment introduction• Creation of a multitude of habitats

for aquatic life• Introduction of logwood and wood

debris



Echo bathymetric monitoringBefore the sediment introduction:

• the Lech stretch shows only little variance in depth

• There is no flow refuge, neither juvenile nor winter habitat

• No spawning ground



After the sediment introduction:

• Increase in depth variance• Increase in habitats provided for

aquatic and amphibic species• Key habitats for umbrella species• Flow refuge and juvenile habitat• Habitat connectivity• Increase in available Ecosystem

Services

Echo bathymetric monitoring



Increase in habitat connectivity

Introduction of macroforms

Introduction of woody debris



Measure Hydromorphological impact

ES affected

Lech



Ecosystem services Case study Action Effect

Habitat related services

Adige River (Ischiello) Removal of levee +Habitat related services

Avisio River, Buech River, Drac River

Artificial sediment replenishment +


Isarco River (Bozen), Lech River (Bayern)

Creation of bedforms and artificial sediment replenishment

+


Talvera River (Bozen),Drava River (Slovenia)

Ensuring environmental flow +


Wertach River (Bayern)

Channel widening +




Water activities Drac River Artificial sediment replenishment +

Water activities Isarco River (Bozen), Adige River (Lana)

Creation of bedforms and artificial sediment replenishment

+

Water activities Drava River (Slovenia) Ensuring environmental flow +Flood risk mitigation Wertach River

(Bayern)Channel widening +

Flood risk mitigation Drac River Artificial sediment replenishment +

Hydropower Drava River Ensuring environmental flow -




Education of science Adige River (Ischiello) Removal of levee +Cultivated crops Adige River (Ischiello) Removal of levee -Aesthetics of landscape

Drac River Artificial sediment replenishment +





Thank you!Merci!Danke!Grazie!Hvala!

…the morphology and sediment transport of alpine rivers have been strongly altered during the last...

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