The use of X-band polarimetric radar to assess the impact of different temporal and spatial resolution on a drainage system in Rotterdam urban area

Abstract

This study aims to assess the impact of different temporal and spatial rainfall resolutions on the hydrological response of a higly urbanized area. The catchment under study is one of the pilot locations of RainGain Interreg IVB project, which aims at improving fine-scale measurement and prediction of rainfall to enhance urban pluvial flood prediction within cities. Heavy rain precipitation can cause catastrophic flooding events over urbanized areas. Accurate information about rainfall is needed to be able to mitigate consequent damages. Due to the high percentage of imperviousness and low rate of vegetation interception, the reaction of urban drainage catchments to a storm event is short. Therefore, to describe fast runoff processes and short response times, urban hydrological modelling requires high resolution rainfall data. Here rainfall from dual polarimetric doppler X-band radar, belonging to the Dutch national meteorological observatory CESAR, is applied to an urban catchment of 3,7 km² that has a combined sewer system with 3062 nodes and 11 external weirs, which serve as outflow. The nodes are inter-connected by 3286 pipes. Among the latter, 4 are pressurized. There are also 2 external pumping stations transporting water to the WWTP and the river. The district belongs to a polder area, i.e. below sea level. For this reason, during heavy rainfall, excess storm water needs to be pumped out in the river system or temporally stored.