Design storms and water quality control

The lack of data can make it impossible, in many cases, to use continuous simulation to predict the impact of stormwater discharged into a receiving water body. The aim of this study is to analyze the impact on receiving water bodies of hydrographs and pollutographs generated by design storms. A recently developed model able to simulate the presence of total suspended solids in stormwater has been used to test different possible design storms and decide which storms provide the highest impact on the receiving water body. Issues related to the evaluation of the length of the previous dry period are briefly examined. The tests carried out show that design storms with triangular or Chicago shapes and durations, similar to the time of concentration of the catchment, are in several cases the worst regarding impact on the receiving water body.