A SOM-based approach to estimating design hyetographs of ungauged sites

Based on the self-organizing map (SOM), an approach is proposed to estimate design hyetographs at ungauged rainfall stations. The proposed approach contains two parts: a SOM-based clustering method and an assigning method. Firstly, the SOM-based clustering method is based to group the design hyetographs at gauged sites. Using the SOM-based clustering method, the relative topological relationships of the design hyetographs at the gauged sites can be established, and the number of clusters can be objectively decided by visual inspection. Furthermore, the assigning method is developed to assign an ungauged site to a specific cluster according to both the spatial information and the clustering results of gauged sites. After the ungauged site is assigned to the appropriate cluster, this cluster's average design hyetograph is adopted as the estimated design hyetograph for the ungauged site. The proposed approach is applied to estimate the design hyetographs of ungauged sites in northern Taiwan. The results show that the approach performs better than methods based on conventional clustering techniques. (c) 2007 Elsevier B.V. All rights reserved.