Floods in urban environments cause substantial damage. Urban flood risk management requires a reliable knowledge of flood hazard, including the flow characteristics in urbanized floodplains. Here we present numerical simulations of flooding in an urban district. The computations are compared against experimental observations obtained from a remarkable laboratory set-up, representing an urban district with 14 streets and 49 crossroads. Data provide a unique benchmark for other numerical models.

We derived mathematical formulations of relations between relative wetness and gradients driving run-off and evaporation for a one-box model such that, when conductances are optimized with the maximum power principle, the model leads exactly to a point on the Budyko curve. With dry spells and dynamics in actual evaporation added, the model compared well with catchment observations without calibrating any parameter. The maximum-power principle may thus be used to derive the Budyko curve.

The current operation rules of two muti-purpose reservoirs are analysed based on an integrated model including a hydrological model, a hydraulic model, a model of the reservoir system and a flood damage model. Five performance indicators have been defined, reflecting the ability to provide drinking water, to control floods, to produce hydropower and to reduce low-flow conditions. Then, impacts of two climate change scenarios are assessed and enhanced operation rules are proposed for mitigation.