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Flood-risk modelling for Randstad conurbation

Development of the largest national 1D/2D model for flood analysis

The Randstad is the most densely populated area of the Netherlands with cities such as Amsterdam, Rotterdam and Utrecht. It is also the lowest area of the Netherlands with levels down to 6 m below mean sea level.
The area is surrounded by water on every side and for drainage of the urbanised and rural areas large systems of interconnected canals exist.
Flooding from the sea, rivers and the canals is a real risk despite the well maintained dikes surrounding the area. Information about flood patterns is necessary to analyse the possible effects of a dike breach and prepare measures such as evacuation plans.

Modelling spatial features

HydroLogic has built and tested a 1D/2D model in Sobek to calculate the flood patterns for the entire area. In order to obtain a high quality elevation model we developed intelligent GIS algorithms that automatically build a model from a DEM (digital elevation model) and topographic information about land use and raised elements such as motorways and dikes.
The algorithms convert the very detailed 0.5 x 0.5 m data in the DEM to an elevation model suitable for modelling floods with any desired resolution. The algorithms were construed in an unambiguous way resulting in a transparent and reproducible flood model.

Use of the model

This project was commissioned by the provinces of Zuid-Holland, Noord-Holland and Utrecht and has been developed in cooperation with the various water boards in the Randstad region. The project result is used by the clients and consultant companies for spatial flood risk analysis and the development of calamity plans. 





 


Modelling at various resolutions (5, 50 and 100 m grids).