Quantitative rainfall analysis and flow simulation for an urban catchment using input from a weather radar

Abstract

In the majority of small urban catchments, there is a problem with obtaining precipitation data necessary for hydrological applications and analyses in the scope of assessing flood risk. One of the means of measuring rainfall depth is to make use of weather radar technology, which provides information on the spatial and temporal distribution of rainfall in a catchment. In the work, the dependency between radar reflectivity (Z) and rainfall rate (R) was determined on the basis of a few events measured at two precipitation stations located in the Służewiecki Stream catchment in Warsaw, Poland. Making use of the Z-R relationship as well as values of radar reflectivity, the amount of rainfall for the analysed event was calculated and compared with the amounts of rainfall measured using rain gauges. Relatively good compatibility between the rainfall totals was obtained for the majority of events. Rainfall depths obtained for two selected events on the basis of data from the weather radar were applied to simulate flows in the analysed catchment using the SWMM (Storm Water Management Model) hydrodynamic model. Values of the relative error calculated on the basis of measured flows and flows calculated in reaction to rainfalls estimated using the Z-R relationship were, in the majority of cases, lower than 25%. Simulations carried out on the SWMM model for a few rainfall scenarios in response to rainfall depth measured at precipitation stations and estimated on the basis of radar data revealed the possibility of the occurrence of flooding in the catchment as a result of the overflow of rainfall collectors.