Dynamization of Urban Runoff Pollution and Quantity

At present, the annual loads from long-term series simulations are mostly used for the evaluation of rainwater management and treatment measures although the relevance of the temporal distribution of both pollution and quantity has a recognizable influence on the performance of the treatment. With the idea of dynamizing the simulation output values in relation to (i) single rainfall events, (ii) specific catchment characteristics, and (iii) the duration of the dry period between two rainfall events measurement devices and scenario studies were established in a joint research project in Lower Saxony. First measurement results of surface runoff qualities of an urban sub-catchment in Braunschweig/Germany are presented in a high temporal definition for several pollution parameters. A correlation analysis was performed identifying additional explanatory parameters that have an influence on the first flush effect, such as rainfall characteristics or antecedent dry period. First calculations of the possible reduction in the decentralized storm water treatment by disconnecting the first flush showed values of 42-65%, depending on the pollution parameters. The comparative evaluation of the data with different statistical methods shows that the uncertainties in the calculation of rainwater pollution, or the duration of the first flush, are still very high and do not yet allow researchers to derive a pollution forecast for, e.g., a throttle control solely from the recording of the rain and area characteristics.

Automated summary

Currently, annual loads from long-term series simulations are commonly used to evaluate rainwater management and treatment measures, although the temporal distribution of pollution and quantity has a noticeable impact on treatment performance. A joint research project in Lower Saxony established measurement devices and scenario studies to dynamically simulate output values in relation to rainfall events, catchment characteristics, and dry periods. First measurement results of surface runoff qualities in an urban sub-catchment in Braunschweig, Germany were presented, along with correlation analysis identifying additional explanatory parameters for the first flush effect.