Rainfall is an important element in the hydraulic modelling of Urban Drainage Systems, as it directly contributes to runoff. Hence any inaccuracies caused by poor measurement or inappropriate use of rainfall data will have a direct consequence on the outputs from the hydraulic modelling process.
It is the intention of this good practice guide to provide to the Urban Drainage practitioner a summary of current good practice in the UK industry. This will of course be a snapshot of the current available methods and processes.
The guide has been split into three main sections, being:
· Modelling of rainfall for model verification
· Modelling of rainfall in design – design storms and long-time series
· Modelling climate change effects.
Although included in a separate section, the effect of climate change is an integral aspect of the use of rainfall in design. The guide is specifically written to cover the rainfall aspects of hydraulic modelling, and associated parameters such as antecedent conditions and evapotranspiration. It is not intended to cover any other aspect of the hydraulic modelling process. The main emphasis of the guide is related to the requirements for the modelling of wastewater and storm water networks, rather than the modelling of large watercourses.