Flood Lines
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African Environmental Development are one of a few companies with the capacity to model flood lines under South African rainfall conditions. Subsequently, the flood lines we produce are accepted by all authorities.

Download a PDF version of our 2016/2017 price list by clicking on this link: AED Quotation RSA Flood Lines 2016.pdf

A Computer- Generated Image of a river, the 50- and 100-year flood lines (Blue and yellow lines), a double line railway bridge and the existing surface infrastructure in the vicinity of the river.

Firstly, we model a series of "Design Storms" with durations ranging from 1 up to 100 hours (depending on the size of the catchment), using the methods described in the University of the Witwatersrand Dept of Civil Engineering Hydrological Research Unit Report No. 1/72 “Design Flood Determination in South Africa”. Depending on various factors built into the simulation, the model provides us with a water discharge rate in m³/s and a time-frame over which the peak of the flood would occur.

The next step is to accurately survey the banks of the river or stream and to produce a number of cross sections through the stream or river valley. These will then be used to plot the elevation points of the flood line at that particular cross section.

A number of cross sections through the river valley is used to plot the flood line on either side of the river.

Once a profile of the stream or river valley has been made, the flood volume determined above, is routed through the cross sections using several factors such as slope, Mannings roughness coefficients for open channel flow, etc. and the actual flood elevation is derived using Report No 1/74 “A Simple Procedure for Synthesizing Direct Runoff Hydrographs” of the University of the Witwatersrand Dept of Civil Engineering Hydrological Research Unit. 

The flood elevations are plotted on either side of the stream/river and the points are linked smartly to produce two continuous lines, one on either side of the stream.

The flood lines we produce are done in accordance with the official methods developed specifically for South African conditions and are accepted throughout South Africa by all Government Departments. We can produce flood lines with return periods from as short as 2 years up to 100 years. The flood lines are made available in DXF format (or any other CAD format) to the client ,using whichever co-ordinate system the client prefers.