oa Civil Engineer in South Africa - Risk and its control in urban stormwater management
Recent events have initiated this review of current urban stormwater management practices, with the aim of stimulating debate. Owing to population pressures the urban environment contains special problems for the hydrologist. The administrative authority has to contend with several, often conflicting, demands on land use. Risk evaluation is generally done in a quantitative fashion only. Probability-related hydrological data is used to obtain a flood peak, which in the case of watercourses is used to calculate a flood level. In township areas above this level flood peaks are used to design a reticulation system, while in those below the specific flood level development restrictions are imposed. The paper questions certain aspects of this procedure, emphasizing the need for a qualitative assessment.
The control of risk is discussed in terms of development controls. phvsical controls and the control of the secondary effects of flooding. The adequacy of existing legislation relating to flood plain development and of contingency plans in the event of severe flooding is queried. The assumption that the administrative authority is solely responsible for controlling the risk of flooding is examined.
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