Documents on the proposed development of JP Bezuidenhout Park and Horwood’s Farm show 50-year and 100-year flood lines. The flood on 9 November 2016 reached and slightly exceeded the 50-year flood line opposite the sports fields.
South of where the Harmelia Stream crosses Main Road (just off the map provided so one needs to extrapolate) the flood levels were probably well over the 50-year flood line. This is because the run off from Meadowdale industrial area crossed the R24 Freeway, overflowed the Buurendal retention dam, and flowed directly through Buurendal, Highway Gardens and Hurlyvale suburbs to arrive at this point. The photo below shows the maximum level of the water in Main Road between North Road and South Road. This was mainly due to the flood through the suburbs. See also Rainfall and Jukskei Rive Catchment Information and Edenvale Stream.
What can we learn from this?
First, the flood lines used in the documents for the proposed development show residential buildings inside the 50-year flood line, while the 100-year flood line includes up to three rows of houses. At the time they were built they would have been outside any flood risk area. As run off increases the flood lines have to be expanded, and those that were safe are no longer so.
Second, the response of the local authority to the increased flooding from the Meadowdale development has in the past been too little too late. The Buurendal retention dam is completely inadequate. The Eastleigh Stream is too constricted to cope with the current run off and further development in the catchment will make things worse.