The Use of a Flood Damage Rating System to Aid Urban Stormwater Managementby M. Braune, Robertson & Kirsten Inc, Johannesburg, South Africa,
B. J. Middleton, Robertson & Kirsten Inc, Johannesburg, South Africa,
Abstract: Increasing urbanisation and the subsequent decrease in natural storage and infiltration potential in a catchment, cause increased runoff peaks and volumes. Existing stormwater drainage systems become inadequate to handle increased runoffs, causing flooding to occur more frequently, in turn damaging property and endangering life. A unique damage rating system, which takes into account applicable stormwater system design standards, has been developed to identify, quantity and rank areas according to the flooding hazard. From the damage rating system an urban catchment can be sub-divided into high, medium and low damage potential zones. Should no stormwater system design standards be available, a method to select the most cost-beneficial design standards using a Benefit Factor, which relates the risk of flooding to the capital cost of the drainage system, has been developed. Remedial measures are then identified to reduce the flooding potential. A phased remedial works programme is compiled, in which the required remedial work is prioritised to reduce the flood damage potential in the shortest possible time. In this paper the above concepts are defined and illustrated by abstracting relevant information from a Stormwater Management Project undertaken for the Welkom City Council.
Subject Headings: Stormwater management | Drainage systems | Floods | Damage (structural) | Ratings | Urban areas | Runoff | Hydraulic design
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