Regional approach for the analysis of annual maximum daily precipitation in northern Morocco

Information on extreme rainfall frequencies is required for Urban Drainage (UD) networks design. In this paper, the Regional Frequency Analysis (RFA), based on the L-moments, is used to: (i) analyze the trend of Annual Maximum Precipitation (AMP) over two analysis periods (1970–1989 and 1990–2015), (ii) estimate the regional Intensity-Duration-Frequency (IDF) curves of northern Morocco and (iii) assess the impact of the changes in rainfall intensities on the UD networks design during analysis periods. In reference to Hosking & Wallis (1997) and Alila, (1999), the Generalized Extreme Value (GEV) distribution has been used as a regional distribution to estimate regional quantiles for the analysis periods (1970–1999 and 1990–2015). The results show an increase up to 9% for quantiles used in UD networks design.