Impact of rainfall data resolution in time and space on the urban flooding evaluation

ABSTRACT Climate change and the modification of urban environment increase the frequency and the impact of flooding rising the interest of researchers and practitioners on this topic. Usually flooding frequency analysis in urban areas are indirectly carried out by adopting advanced hydraulic models to simulate long historical rainfall series or design storms. However their results are affected by a grade of uncertainty which has been much investigated in recent years. One of the most critical source of uncertainty inherent to hydraulic model results is linked to the imperfect knowledge of the rainfall input data both in time and space. Several studies show that hydrological modelling in urban area needs that rainfall data have fine resolution in time and space. The present study aims to analyse the effect of the resolution of rainfall input both in space and in time. The analysis used flooding depths and damage as references to assess the impact of rainfall knowledge on urban flooding modelling results. To this aims, with regard to a case study, the maximum efficiency conditions for the model and the uncertainty affecting urban flooding modelling results were evaluated by the means of GLUE analysis and the added value provided by the adoption of finer temporal and spatial resolutions were assessed.