To study the impact of urban dynamics on hydrology a rainfall-runoff modelling strategy is used. The WetSpa model is adapted for flexible input from remote sensing derived parameters (as described in WP10 ). A case-study for the River Tolka in Dublin ( Ireland ) is developed. Firstly, the WetSpa model is developed and calibrated for the period 1985-2005 using the outputs of WP10. In a second phase, future spatial flood risk will be assessed using a predictive modelling based upon the land use scenario maps obtained from WP7.

The WetSpa model is a physically based, fully-distributed rainfall-runoff model (for details: see WetSpa website ). The model needs spatially distributed input (see figure upper-left): a digital elevation model, a soil map, a landuse map and meteorological data (timeseries of precipitation, potential evapotranspiration, temperature, etc.). Within the framework of the MAMUD project also remote sensing derived input is integrated into the model as described in WP10 . For the assessment of future spatial flood risk the land use scenario maps, generated in WP7, will be used in rainfall-runoff modelling.

The main outputs are simulated river discharge time series and spatially distributed runoff maps. These runoff maps can be translated to flood risk maps for the Tolka catchment. The lower-left figure shows some preliminary results. The graph shows the hydrological response (river discharge Q s - left axis) for the same rainfall events (vertical bars - right axis). The blue and red lines show the hydrological response for the years 1988 and 2001 respectively. For both years the sub-pixel maps with % sealed surface (from WP2) were integrated into the model. Note the clear difference between the 2 situations, with considerably higher discharge for 2001, due to higher runoff coefficients (see WP10).