Smart Rivers International Conference 2017 - RemTech Expo Ferrara, September 22nd, 2017
MONITORING MORPHOLOGICAL CHANGES IN A RESTORED REACH: THE SPREE RIVER
Michael Nones 1, Arianna Varrani 2 1
CIRI-EC, University of Bologna, Italy -
[email protected]
2
Brandenburg University of Technology, Cottbus, Germany -
[email protected]
MONITORING
MORPHOLOGICAL CHANGES IN A RESTORED REACH: THE
SPREE RIVER
Monitoring of sediment transport is not explicitly mentioned in the WFD. Hydro-morphology is considered only as supporting element in the case of water bodies classified in good or lower status (WFD).
No requirements regarding sediments in the Floods Directive.
sediments 2/17
MONITORING
MORPHOLOGICAL CHANGES IN A RESTORED REACH: THE
SPREE RIVER
WFD ecological classification system describes hydromorphological elements as “supporting the biological elements”.
Assessment of pressures and impacts on: • hydrological regime (quantity and dynamics of flow, connection to groundwater) • continuity (ability of sediments and migratory species to pass freely up and down rivers and laterally with the floodplains) • morphology (physical habitat, compositions of substrate, width/depth variation, structure of bed, banks, riparian zone)
3/17
MONITORING
MORPHOLOGICAL CHANGES IN A RESTORED REACH: THE
SPREE RIVER
S= 6240 ha (62 km2)
L= 11 km Qmean= 7.5 m3/s
Qbankfull= 35 m3/s d50= 0.66 mm
4/17
MONITORING
MORPHOLOGICAL CHANGES IN A RESTORED REACH: THE
SPREE RIVER
Construction of islands and meanders
Lowering river banks and planting of natural vegetation
Relocation of dykes and main channel
5/17
MONITORING
MORPHOLOGICAL CHANGES IN A RESTORED REACH: THE
SPREE RIVER
High water levels and floods cause sediment deposition on floodplains and bed/bank erosion. Problems: • narrowing and deepening of the river bed • reduction of planimetric variability: single thread channel • threats for habitat and ecological status (failure of the WFD goals) • increase of flood risk (failure of the FD goals) • failure of the restoration project Integration of a sediment management plan in the implementation programme of the WFD/FD.
6/17
MONITORING
MORPHOLOGICAL CHANGES IN A RESTORED REACH: THE
SPREE RIVER
restoration works 2006-2014 aerial images 2005-2015
source: Vattenfall Europe Mining AG
7/17
MONITORING
MORPHOLOGICAL CHANGES IN A RESTORED REACH: THE
SPREE RIVER
Available data • aerial images (2006-2014) • DGMs (2005 and 2014) • bathymetric surveys (2003-2014) • river discharge • water stage • sedimentological samples • fish • macrozoobenthos • fauna • vegetation
year
aerial images
river discharge
acquisition date
[m3/s]
2006
6 June
7.00
2007
7 June
6.39
2008
8 May
6.39
2009
9 July
15.40
2010
10 June
30.40
2011
11 May
15.10
2012
12 June
8.75
2013
17 June
65.90
2014
14 May
13.50
2015
31 May
5.00
Problems ==> Management solutions • deposition along floodplains and bed/bank erosion during high flow conditions • narrowing and deepening of the main channel • reduction of planimetric variability: single-thread river • reduction of habitat and ecological status (failure of the WFD goals) • increase of flood risk (failure of the FD goals) • failure of the restoration project 8/17
MONITORING
MORPHOLOGICAL CHANGES IN A RESTORED REACH: THE
SPREE RIVER
Monitoring of the river morphology
Pt Lt Lr
BI Li Lt
S Li Lr
Pt = thalweg sinuosity BI = braiding index S = total sinuosity
Li Lt Ls
Nones & Gerstgraser, 2016
Evaluation of the project outcomes
r ln X r X c
r = response ratio Xr = parameter post-restoration
Xc = parameter pre-restoration Osenberg et al., 1997; Miller et al., 2010; Whiteway et al., 2010; Kail et al., 2015
9/17
MONITORING
MORPHOLOGICAL CHANGES IN A RESTORED REACH: THE
SPREE RIVER
thalweg sinuosity
braiding index
total sinuosity
2.0
1.5
1.0
2013 flood
0.5 2006
2007
2008
2009
2010
2011
2012
2014
2015
10/17
MONITORING
MORPHOLOGICAL CHANGES IN A RESTORED REACH: THE
SPREE RIVER
2005
2014
source: Vattenfall Europe Mining AG
11/17
MONITORING
MORPHOLOGICAL CHANGES IN A RESTORED REACH: THE
SPREE RIVER
Lack of detailed measurements Bed erosion visible in the latest surveys
12/17
MONITORING
MORPHOLOGICAL CHANGES IN A RESTORED REACH: THE
SPREE RIVER
Using the input data monitored along the course, two numerical models were applied:
• CAESAR-Lisflood is a 2D grid based LEM that uses a hydrological model (an adaptation of the TOPMODEL) to generate surface runoff, which is then routed using a separate scheme generating flow depths and velocities, used to drive fluvial erosion over several grain sizes integrated within an active layer. • HEC-RAS 5.0 is the last version of the code released by USGS, able to perform 1D unsteady-flow modeling, 2D unsteady-flow modeling, combined 1D and 2D unsteady-flow routing. The code was used to simulate the flooded areas at the 2D scale.
13/17
MONITORING
MORPHOLOGICAL CHANGES IN A RESTORED REACH: THE
SPREE RIVER
CAESAR-Lisflood
HEC-RAS 5.0
14/17
MONITORING
0.60
MORPHOLOGICAL CHANGES IN A RESTORED REACH: THE
SPREE RIVER
r ln X r X c
response ratio r
0.40
0.20
0.00
-0.20 2002
2004
thalweg sinuosity
sources: Vattenfall Europe Mining AG
2006
2008
braiding index
BTU Cottbus
2010
total sinuosity
Institute of Inland Fisheries, Potsdam-Sacrow
2012
fish
2014
2016
macrozoobenthos
15/17
MONITORING
MORPHOLOGICAL CHANGES IN A RESTORED REACH: THE
SPREE RIVER
• The Spree River is affected by • problem of fine sand transport during high flow conditions • excessive deposition along secondary channels and floodplains • diffuse erosion along the main channel
• Increasing the number of channels, redesigning their shape and adding coarser sand could be not sufficient to improve the ecological status of rivers and fulfill the WFD goals. • Analysis of hydromorphological quality elements during the ecological assessment procedure is highly recommended, regardless of the river biological status. • An integrated analysis of all the fluvial aspects represents a fundamental way to fulfill the WFD (and FD) requirements at a reasonable temporal scale. 16/17
Smart Rivers International Conference 2017 - RemTech Expo Ferrara, September 22nd, 2017
THANK YOU FOR YOUR ATTENTION
Acknowledgements: This work was supported by the Research Executive Agency, through the 7th Framework Programme of the European Union, Support for Training and Career Development of Researchers (Marie Curie – FP7-PEOPLE-2012-ITN), which funded the Initial Training Network (ITN) HYTECH “Hydrodynamic Transport in Ecologically Critical Heterogeneous Interfaces”, N. 316546. Restoration project and monitoring programmes were made in collaboration with gerstgraser Ingenieurbüro für Renaturierung, Vattenfall Europe Mining AG, BTU Cottbus and Institute of Inland Fisheries, Potsdam-Sacrow.
