Calculation of the secondary effects of floods in the lower Orange River area - A GIS approach

This article forms part of a series published in Water SA (commencing in Vo l. 23 No. 3, July 1997 and Vol. 24 No. 3, July 1998) and builds on the info rmation contained in the previous articles. Construing loss functions and f lood damage simulation models as well as the assessment of the total direct flood damage have already been discussed in the mentioned articles. From t he above mentioned knowledge, it is possible to estimate the secondary effe cts of floods with different probabilities of occurrence. For this purpose damage is considered and assessed from a regional and national point of vie w. In the economy of a country there are forward and backward linkages betw een different sectors. This implies that the real impact of floods has wide r implications than the merely direct and this is one of the reasons why th e secondary effects nf floods are assessed. The flood plain of the Orange River, downstream from the Gifkloof Weir up t o the Manie Conradie Bridge at Kanoneiland was used as study area for the r esearch. The aim of the article is to determine the secondary effects of floods from a regional and national point of view. First of all a methodological revie w is provided, after which the secondary effects of floods for the studied area are indicated.