Contributions by HACH ULg to ADAPT Hydrodynamic modelling, damage evaluation and technical adaptation measures

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1 Contributions by HACH ULg to ADAPT Hydrodynamic modelling, damage evaluation and technical adaptation measures Research unit of, 10 January 2008 B.J. Dewals, S. Detrembleur, P. Archambeau, J. Ernst & Prof. M. Pirotton

2 Location of the Ourthe case study The sub basin of the River Ourthe Located in the province of Liège Near the junction between rivers Ourthe and Meuse The studied sections lie between Poulseur and Tilff Total distance : almost 20 km (~11 km studied) Corresponds to the limits of the municipality Esneux

3 Case study Ourthe: progresses on four complementary issues TASK 2.1 Primary impacts of global change induced flooding on river basins Sub task (a) Sub task (b) Hydrodynamic modelling of floods on the River Ourthe, considering climate change Translating results of hydrodynamic simulations into input for the evaluation of secondary impacts TASK 2.2 Secondary impacts of global change induced flooding on river basins Contribution to integrating results of hydrodynamic simulations with economic damage evaluation TASK 2.3 Determining and evaluating adaptation measures Sub task (a) Sub task (b) Litterature review of flood protection measures Review of existing technical flood protection measures Hydrodynamic modelling of floods on the River Ourthe, considering climate change and adaptation measures

4 Impacts of Climate Change on inundated areas (River Ourthe) Limited uncertainty in the hydraulic model WOLF 2D Highly accurate Digital Elevation Model Calibrated friction coefficient and possible turbulence modelling (incl. k ε closure) Validity of the steady state approach verified by comparing with unsteady simulations based on real hydrographs

5 Impacts of Climate Change on inundated areas (River Ourthe) Hydrodynamic simulations performed with two different return periods (leading to different adaptation strategies) with four (instead of three) different climate change scenarios («guessed» perturbation factors, to be confirmed) Optimistic Q ~5% Mean Q ~ 10 % Pessimistic Q ~ 15 % Extreme Q ~ 30 % 25 year flood Q = 726 m³/s Q = 762 m³/s Q = 799 m³/s Q = 835 m³/s Q = 944 m³/s 100 year flood Q = 876 m³/s Q = 920 m³/s Q = 964 m³/s Q = 1007 m³/s Q = 1139 m³/s

6 Impacts of Climate Change on inundated areas (River Ourthe) 6 new flood maps: discharge increase by 30% Water depth (m) Change in water depth (m) Flow velocity (m/s) 100 year 25 year return period IN TOTAL: 2 x 4 x 3 maps + 2 x 2 maps (base scenario) 24 updated floodmaps + 4 reference floodmaps

7 Integrating hydrodynamic modelling and economic damage evaluation Task 2.1(a) Task 2.1(b) Hydrodynamic modelling (flood maps for River Ourthe) Translation of hydrodynamic results Task 2.2 Economic evaluation Social evaluation Ecological evaluation

8 Integrating hydrodynamic modelling and economic damage evaluation FLOOD RISK = sum ( probability * consequences) Probability Consequences (actual predicted damage) Probability Exposure Elements at risk Vulnerability (return period) (extent, depth, veloci ty) (people, buildings, n etworks, ecosystems ) IGN database Landuse (susceptibility, adapti ve capacity, resilience, ) Flood maps Economic value of elements-atrisk Damage functions

9 Integrating hydrodynamic modelling and economic damage evaluation IGN database Landuse map ING Top10v GIS (Layer landuse.shp) Vector data : collection of point, line, polygon from IGN in GIS file format (.shp) Scale 1: layers (administration data, altimetry, electricity, land use, structure, ) Class of object selection from Top10v GIS data Residence Industry Road network Agriculture (Crops, fields) Forestry Result (1 flood)

10 Developed methodology STEP 3 Relative damage determination Water depth and Residence (grey) Mesh used for water depth calculation (green) STEP 4 Economic damage evaluation Relative cost of floods Relative amount Declared amount (commune) Accepted amount (commune) Calculated amount (town of Tilff) m³/s

11 Case study Ourthe: progresses on four complementary issues TASK 2.1 Primary impacts of global change induced flooding on river basins Sub task (a) Sub task (b) Hydrodynamic modelling of floods on the River Ourthe, considering climate change Translating results of hydrodynamic simulations into input for the evaluation of secondary impacts TASK 2.2 Secondary impacts of global change induced flooding on river basins Contribution to integrating results of hydrodynamic simulations with economic damage evaluation TASK 2.3 Determining and evaluating adaptation measures Sub task (a) Sub task (b) Litterature review of flood protection measures Review of existing technical flood protection measures Hydrodynamic modelling of floods on the River Ourthe, considering climate change and adaptation measures

12 Task 2.3(a): Determining adaptation measures HACH ULg s contribution: litterature review of (technical) adaptation measures (i.e. flood protection measures) Output: Critical discussion of the main technical adaptation measures Reliability Operation Maintenance List of references Link with a similar study by the partners: Cost, Potential environmental impact, Public acceptance,

13 Litterature review on technical adaptation (flood protection) measures Drainage in the protected area Visual and environmental impact Maintenance required Risk of failure Mobile dikes Require a warning system Maintenance Land rising Reduced water depth in case of extreme flood Less drainage required in the protected area Need for compensation upstream (retention basin, channel widening) + Cost

14 Task 2.3: Determining adaptation measures (a) Literature review / review of existing measures FLOOD RISK = sum ( probability * consequences) Probability Consequences (actual predicted damage) Probability Exposure Elements at risk Vulnerability (return period) (extent, depth, veloci ty) (people, buildings, n etworks, ecosystems ) (susceptibility, adapti ve capacity, resilience, ) Mitigation measures (source oriented : reduce run off) Adaptation measures (effect oriented: reduce flooding for given run off) Mitigation measures (preventive: limit use of floodplains) Adaptation measures (curative: reduce the impact of flooding)

15 Case study Ourthe: progresses on four complementary issues TASK 2.1 Primary impacts of global change induced flooding on river basins Sub task (a) Sub task (b) Hydrodynamic modelling of floods on the River Ourthe, considering climate change Translating results of hydrodynamic simulations into input for the evaluation of secondary impacts TASK 2.2 Secondary impacts of global change induced flooding on river basins Contribution to integrating results of hydrodynamic simulations with economic damage evaluation TASK 2.3 Determining and evaluating adaptation measures Sub task (a) Sub task (b) Litterature review of flood protection measures Review of existing technical flood protection measures Hydrodynamic modelling of floods on the River Ourthe, considering climate change and adaptation measures

16 Task 2.3: Determining adaptation measures Preliminary test of technical adaptation measures Reduced water depth upstream (50 cm) as a result of the activation of a flood control area (topography and flow velocity in Poulseur) Input for integrated assessment

17 Summary and conclusion 6 new flood maps, assuming a more extreme perturbation factor affecting flood discharches Inititation of integration between results of hydrodynamic modelling and economic damage evaluation (in progress) Initiation of the review of adaptation measures (focus on technical flood protection measures, in progress) Preliminary test of hydrodynamic modelling of adaptation measures Detailed quasi 3D modelling of the case study Ourthe fully operational to provide useful hydrodynamic results for the socioeconomic and evironmental evaluation of adaptation measures