Urban Flood Modelling in Dhaka

In the latest module at UNESCO-IHE, we have been given a selection between Urban Flood Modelling and River Basin Modelling. The splitting of our course has given us the opportunity to delve deeper into the aspects of flooding that most interest us and I believe all on the course can agree that the opportunity to select a course preference has been greatly rewarding.

Flood Hazard Map
by Siobhan Gleeson

Those on the FRM course who chose the Urban Flooding route have spent a considerable time creating (surprisingly) sophisticated models of Bangladeshi floods in the city of Dhaka. The main project that we have worked on in the course's three week duration, has been the creation of a 1D-2D coupled model. This has involved taking a 1D model of an urban drainage network (created on DHI's MOUSE software) and coupling (or, in less technical terms, 'linking') it to a 2D model, representing the surface topology (using MIKE 21). The surface model was created on a highly fine resolution (2.5m) and, accordingly, is able to accurately include road recesses, and micro-topology features, such as alleyways, in addition to accurately recording buildings. With such high resolution data, the models are very accurate in their representation of reality.

After the models were ran, complex flood risk maps were created on ARC GIS and analysed (as picured). This is a process that is a key component of the EU Flood Directive's recommendations, with all EU nations agreeing to have created extensive flood risk maps by September 2013. Accordingly, the work we are doing is extremely pertinent to the flooding sector upon our graduation and is likely to be relevenent to the working world upon our graduation.

As part of these models we were also able to plot the flood event in 3D through the streets of Dhaka. The below video displays the maximum water depth for the model with both buildings and on a bare-earth model. The building model is useful to demonstrate the height of water that will impact buildings, and the maximum wave heights can be seen by the blue 'splashes' on the sides of some buildings. The bare-earth model is of use to determine which buildings will be affected by the flood event, without the disruptances of flow that buildings provide - accordingly, this is the model that we use to create our flood risk maps.


Hope you enjoyed the video. And hope you equally enjoyed its Daft Punk soundtrack.

by Richard Vause