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Expected impact of Climate Change on flooding in the Dender Basin. Results MSc thesis: Adaptive measures to reduce climate change impacts on flood probabilities. Niels Van Steenbergen & Jeroen Verbelen Expected impact of CC in Dender Basin • • • • 3 climate scenarios CCI-HYDR Perturbation Tool Perturbation factors Composite hydrograms (T= 5, 10, 25, 100, 250) Expected impact of CC in Dender Basin • Conceptual model • Hydrodyn. model – Linear reservoir – Calculation time 10² s – Simplification – Calibration – Measures – Saint Venant – Calculation time 104 s – Accurate – Detailed Expected impact of CC in Dender Basin • Conceptual model of the upstream Dender basin Q river H river Q flood H floodplain Q-H relation Hdiike weir Q-V relation Expected impact of CC in Dender Basin • Floodmapping of conceptual model – – – – Method of fictive floodbranches Floodbranch in the lowest point Water height as boundary of the floodbranch Extrapolation of water height in polygon HW d H (DEM) Hw Expected impact of CC in Dender Basin • Simulation results (climate scenarios: red = low, orange = mean, green = high, blue = normal) (T=10) Expected impact of CC in Dender Basin • Simulation results (climate scenarios: red = low, orange = mean, green = high, blue = normal) (T=10) Expected impact of CC in Dender Basin • Simulation results (climate scenarios: red = low, orange = mean, green = high, blue = normal) (T=10) Adaptation scenarios considered and the expected impact on flooding in the Dender basin. Results MSc thesis: Adaptive measures to reduce climate change impacts on flood probabilities. Niels Van Steenbergen & Jeroen Verbelen Adaptation Scenarios in Dender Basin • Adaptation scenarios – Baseline scenario = Situation before the flood 20022003 – Scenario 1 = dikes built in 2003 – Scenario 2 = scenario 1 + adapted weirs – Scenario 3 = scenario 2 + flood control reservoirs • Marke + Molenbeek Zandbergen • Spatially concentrated • Assumption on filling and emptying Adaptation Scenarios in Dender Basin • Scenario 1: dikes – – – – T = 25 year Climate Scenario = Mean Blue = Baseline Red = Scenario 1 Adaptation Scenarios in Dender Basin • Scenario 2: weirs – – – – T = 25 year Climate Scenario = Mean Red + Green = Scenario 1 Green = Scenario 2 Adaptation Scenarios in Dender Basin • Scenario 3: flood control reservoir – – – – T = 25 year Climate Scenario = Mean Green + Orange = Scenario 2 Orange = Scenario 3 Adaptation Scenarios in Dender Basin • Other inundation parameters – Water rise rate – Water velocity in floodplains Historical events Adaptation Scenarios in Dender Basin • Other inundation parameters – Rise rate (1995) Adaptation Scenarios in Dender Basin • Other inundation parameters – Water velocity in floodplains (2002-2003) • Criterion : < 2 m/s Adaptation Scenarios in Dender Basin • Conclusions – Calculation time – Measures • Dikes: most positive influence, but can cause problems upstream • Weirs: positive influence, but can cause problems downstream • Flood control reservoirs: small influence, but most desirable measure Improvement of efficiency - Other possible measure: - Lowering dikes in non-built area’s