Grant: EP/FP202511/1 Advances in Flood Risk Management Science - Improved short term rainfall and urban flood prediction Prof. Čedo Maksimović Nuno Simões, Li-Pen Wang, Susana Ochoa The Royal Society, London, 5 th September 2011

Contents: Urban flood modelling – Dual-drainage models Radar-based integrated rainfall forecasting – Methodology and key techniques – UK case study: Cranbrook catchment, Redbridge Rainbgauge-only-based spatial-temporal rainfall prediction – Methodology and key techniques – Portugal cast study: Coimbra Remarks

URBAN FLOOD MODELLING Focus on estimating fast and reliable flood distributions over the target urban areas

1D/2D, 1D/1D and Hybrid models 1D Sewer Simulation 1D / 2D simulation 1D / 1D simulation Hybrid 1D/1D + 1D/2D simulation

Interaction between 1D Overland Network and 2D Overland Network

1D-1DHybrid1D-2D

Simulation time EventModel[hh:mm:ss]vs 1D1Dvs hybrid 300 min 30 yr 1D1D00:01:46 Hybrid00:04:31156% 1D2D00:45:232469%905% 300 min 100 yr 1D1D00:02:11 Hybrid00:05:20144% 1D2D01:11:103160%1234% 300 min 200yr 1D1D00:04:40 Hybrid00:05:4925% 1D2D01:16:051530%1208%

RADAR-BASED INTEGRATED RAINFALL FORECASTING Integrate state-of-the-art rainfall forecasting and modelling techniques to produce reliable rainfall forecasts as inputs for urban pluvial flood modelling/forecasting

Radar-based integrated rainfall prediction

Cranbrook catchment, London, UK The drainage area of the Cranbrook catchment is approximately 910 hectares; the main water course is about 5.75 km long, of which 5.69 km are piped or culverted.

Uncertainties of using rainfall nowcasts over different spatial and temporal scales for event 2010/08/22-23.

Uncertainties of applying downscaled rainfall inputs to hydraulic modelling for event 2010/08/22-23.

RAINGAUGE-ONLY-BASED SPATIAL- TEMPORAL RAINFALL PREDICTION Combine local point rainfall information with interpolation techniques to provide reliable rainfall forecasts as inputs for urban pluvial flood modelling/forecasting

Raingauge-only-based rainfall prediction = Time series prediction + interpolation techniques

Example in Coimbra, Portugal

Time series prediction (in 5 minutes): ability to generate extreme values

SSA + SVM time series prediction plus IDW interpolation techniques Prediction of water levels 30 minutes in advance 17h25m17h30m17h35m

Remarks Radar-based integrated rainfall prediction can effectively reflect larger scale weather variation to local scales, but – Accuracy: Data combination techniques – Resolution: Super-resolution radar images / rainfall information Raingauge-only spatial-temporal rainfall prediction exhibits promising predictability, but – Lead time: Improved time series prediction models – Spatial variability: Interpolation techniques Hybrid dual-drainage modelling may be the solution to providing fast and reliable flood prediction, but – Flood prone areas: flood map generation – Calibration: Coupled with image processing techniques Remaining issues Prospective work to address remaining issues