Geographical information system (GIS)-supported sewer-system analysis has major advantages over the use of traditional standalone sewer programs, especially with regard to establishing network topology, input of sewage contribution data, querying, displaying and mapping of results. This paper reports on the development of a GIS-supported sewer analysis software package using ArcView GIS. It supports all the stages of sewer-system analysis, viz. defining the topology of a sewer network, the specification of sewage flow contribution parameters, the allocation of sewage-contributing areas to sewer manholes, hydraulic analysis and displaying the analysis results. A sewer program has been developed for hydraulic analysis and written in Avenue, the internal programming language of ArcView. The sewer program is therefore fully integrated with ArcView, and all the functionality of ArcView is available during the sewer-system analysis. Such an integrated software package where the input data, sewer program, GIS and program results are all dynamically linked is the perfect environment for scenario management. The software package has already been successfully applied to the main sewer system of the Inner Cape Metropolitan Region (Inner CMR), as part of an M.Sc. thesis in Geography and Environmental Studies.

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Extreme flood hydrology in Namibia for the past 30 years has largely been based on the South African Department of Water Affairs Technical Report 137 (TR 137) of 1988. This report proposes an empirically established upper limit of flood peaks for regions called the regional maximum flood (RMF), which could be associated with an annual recurrence interval of 10 000 years. This paper revisits the Kovacs RMF flood model applicable to Namibia, and incorporates 30 years of additional systematic data as well as palaeoflood data into the model. A revised graphical distribution of the K-value zones for Namibia is presented and is proposed to replace the current model. The results confirm the work previously done by Kovacs and, in some places, increase the bounds of the RMF zones. The proposed new model may also contribute to a South African update of the Kovacs model, providing useful information along the southern and eastern borders of Namibia.