Improving hydrological model parameterisation in urbanised catchments: Remote sensing derived impervious surface cover maps

Urbanisation is strongly influencing hydrological processes, often causing a reduction of groundwater recharge and severe flooding. There is an urgent need to approach urban water management in a more sustainable way. The problem analysis, planning and monitoring of sustainable urban water management requires reliable and sufficiently detailed information on the urban environment. The biggest impact of urbanisation on the hydrology is caused by increases in impervious areas. Precipitation over these impervious areas is hindered to infiltrate and will mostly flow overland towards sewers systems. The cover percentage and spatial distribution of impervious areas in a basin is, therefore, a parameter indicating the health status of the basin. Currently, land cover/use parameterisation of most rainfall-runoff models is largely based on classes. Typically, soil and land-use classes are parameterised with values from literature. For example, the impervious area coverage in a pixel determines the infiltration capacity, but is fixed per land-use type. Recently, methodologies have been developed which allow estimating the sub-pixel impervious area based on remote sensing images. This paper describes current methodologies to parameterise urban areas in distributed hydrological models, as well as possibilities of new remote sensing based techniques to parameterise impervious surfaces in hydrological models.