Panthou G., Vischel T., Lebel Thierry, Quantin G., Ali A. (2015). Caractérisation de la structure spatio-temporelle des pluies extrêmes : estimation de courbes IDSF pour la région de Niamey. Houille Blanche : Revue Internationale de l'Eau, (3), p. 58-63. ISSN 0018-6368.
Titre du document
Caractérisation de la structure spatio-temporelle des pluies extrêmes : estimation de courbes IDSF pour la région de Niamey
Panthou G., Vischel T., Lebel Thierry, Quantin G., Ali A.
Source
Houille Blanche : Revue Internationale de l'Eau, 2015,
(3), p. 58-63 ISSN 0018-6368
West Africa is known for having experienced major drought events, but during the last decades numerous floods and exceptional inundations have also struck the region. The flood management is now a major concern for West African countries. Floods can occur at different temporal and spatial scales associated either with meso-scale convective systems that can generate exceptional rainfall totals over a small surface area (a few tens of km(2)) during a short period of time (a few hours), or with 5 to 20 days rainfall accumulations over a large part of the region that cause unusual flooding over large scale watersheds. Intensity-Duration-Area-Frequency (IDAF) curves are interesting tools for two reasons: they are useful for hydraulic structures design as they provide estimates of the return level of heavy rains for several temporal and spatial aggregations and they are helpful to characterize the severity of storms. Obtaining such curves from rainfall networks requires long series, high spatial density and high time-frequency of records. In West Africa, such characteristics are provided by the AMMA-CATCH Niger network. This network is located in the Niamey region where 30 recording rain-gauges (5 minutes series) have operated since 1990 over a 16000 km(2) area. In this study, the IDAF curves are obtained by separately considering the time (IDF) and the spatial (ARF) scales. Annual maxima intensities are extracted for different spatial and temporal resolutions. The IDF model used is based on the concept of scale invariance (simple scaling) to normalize the different temporal resolution of maxima series to which a global GEV is fitted. This parsimonious framework allows using the concept of dynamic scaling to describe the ARF. The IDAF curves obtained describe the distribution of extreme rainfall for time resolutions ranging from 1 hour to 24 hours and space scales between 1 km2 and 2500 km(2).
