Regionalization of extreme precipitation distribution using the principal components of the topographical environment

This paper deals with the regionalization of the extreme rainfall intensiti es in the volcanic island of Tahiti (French Polynesia), and focuses how the method automatically takes into account the topographical relief features. Principal component analysis of a digital elevation model supplies a limit ed set of variables describing the topographical environment. These synthet ic descriptors are linked to the parameters of the rainfall intensity Gumbe l distribution by using a stepwise regression adjusted on 20 point-rainfall records. The model is then applied on a regular 300-points grid node, and interpolated using a spline function to provide an approximation of the plu viometric risk all over the island. In the case of the island of Tahiti, th e relationship between the rainfall parameter distributions and the topogra phical descriptors is very strong, and the method supplies a direct estimat ion, in space, of the rainfall statistics through the regression model. Val idation of the results and comparison with simple kriging interpolation sho w the relevance of the approach. However, more data are needed for a better confidence in the parameter estimation in some areas of the island. This a utomatic and objective method could be applied in any mountainous area, whe re topography has a major influence on the precipitation features, to chara cterize the non-stationarity of point-rainfall statistics in space. (C) 200 0 Elsevier Science B.V. All rights reserved.