Abstract 12 Cities are particularly vulnerable to rainfall-generated floods that are typically characterised 13 by their rapid onset and localised nature. This implies that precipitation and catchment 14 information need to be available at high resolution to reliably predict hydrological response 15 and potential flooding. On the contrary, urban areas constitute a major knowledge gap as most 16 flood risk studies have concentrated on natural basins and records of rain gauges and water 17 level gauges in cities are scarce. While increase in intense precipitation as a result of climate 18 change is expected in many areas around the world, it is at present not possible to assess how 19 this will affect urban pluvial flood risk. Collection of reliable, high resolution data in cities 20 needs to start urgently to build up datasets in support of urban flood risk assessment and to 21 enable detection of changes in flood risk whether these are induced by climate change, 22 urbanisation or other future developments. This study shows how implementation of 23 polarimetric X-band radar can contribute to filling the knowledge gap of flood risk 24 quantification in cities. 2
