Flood risk to Edenvale suburbs from Meadowdale omitted from Flood line Report

The problem *

Edenvale suburbs of Buurendal, Hurlyvale and Eastleigh experience flooding due to development higher in the catchment. In 2018 City of Ekurhuleni commissioned a study of the upper Jukskei River tributaries “to provide the Ekurhuleni Municipality with 1:50 and 1:100 year floodline information of sufficient standard and accuracy in order for the Municipality to make well informed and economically viable decisions on possibilities of implementing remediation measures on the existing and future development and infrastructure affected by a 1:50 and 1:100 year flood.”

The study came into the public participation phase in May 2019 (References). The Floodline Report gave nine priority flood risk sites, but the well-known flood risk to Edenvale suburbs of Buurendal, Highway Gardens, Hurlyvale and Eastleigh was missing. This is because the Floodline Study overlooks the stream and sub-catchment draining central Meadowdale towards Buurendal suburb.

The Flood Line Report also does not correspond with maps elsewhere in this Basic Assessment Application which do show the Buurendal Stream. And it is also at odds with City of Ekurhuleni documents and other evidence relating to the flood of November 2016.

Wrong catchment definition *

The Flood Line Report Figure 5.1 shows the upper catchment of the Eastleigh Stream divided into two sub-catchments, drained by the main Eastleigh Stream (ESTL) in the east (the Harmelia Stream from Klopper Park) and a tributary ESTL1T (Hurlyvale Stream) in the west. In reality there are three streams and three sub-catchments, but the Flood Line Report has treated the east and central sub-catchments as one.  Three maps copied from this Basic Assessment application illustrate this.

  • Appendix G3 Aquatic Study: Figure 3 Aerial photograph in 1952. There are two streams traced in the upper Eastleigh catchment. In the east is the main Eastleigh Stream (Harmelia Stream) while the second is the Buurendal Stream coming from what is now the Meadowdale Industrial Development. The Hurlyvale Stream is not traced, but its path can be made out in the west.
Aerial photo of the Eastleigh Stream catchment in 1952 showing three upper sub-catchments and the Buurendal Stream (from Aquatic report)
Eastleigh Stream catchment in 1952 on aerial photo (from Aquatic report)
  • Appendix G3 Aquatic Study: Diagram from Executive Summary. This shows all three streams and the importance of the central Buurendal Stream.
Map of the Eastleigh Stream catchment in Edenvale showing three upper tributaries including the Buurendal Stream (from Aquatic report)
Map of the Upper Jukskei River catchment showing three upper tributaries of the Eastleigh Stream including the Buurendal Stream (from Aquatic report)
  • Appendix G1 Flood line and Remediation Study Figure 5.1. The blue lines show the streams while the dark lines outline the sub-catchments for the flood line study. The map shows two sub-catchments, clearly treating the central and east sub-catchments as one.
Map with outlines of the catchments for the flood line Study showing only two sub-catchments for the upper Eastleigh Stream
Map with outlines of the catchments for the Flood line Study showing only two upper Eastleigh sub-catchments

What really happens *

The central section of Meadowdale drains toward the Buurendal attenuation dam between Minuach St and Donald Avenue. Development of Buurendal many years ago confined the stream underground. Its path is beneath a servitude passing through the properties from the Buurendal dam to the main Eastleigh Stream at the corner of Cunningham Road and Beverley Road. The underground culvert follows straight lines, and the servitude is visible on maps and on the ground.

When there is excess run off from the central sub-catchment and the dam overflows, the flood takes the natural route which is across the suburbs, which is different from the direct underground route. At the lower end it flows into Horwood’s Farm and Eastleigh Stream via Station Road, South Road, North Road and adjacent properties. It does not flow into the Eastleigh Stream at Cunningham Road bridge or higher upstream.

The flood of November 2016 *

A study of the rainfall of 9 November 2016 (References) found it lay between a 1:100 year and a 1:500 year event, while the current study determined 1:50 Year and 1:100 Year Flood lines. The study should have some reasonable correlation with what happened that day.

The November 2016 event flooded an estimated 80 properties through Buurendal, and at South Road there was a dramatic rescue of a child swept out of a house.  Newspaper reports and my review of the event “Buurendal floods and Meadowdale development” give specifics of the damage caused by this flood.

City of Ekurhuleni document “SCHEDULE FOR THE CLASSIFICATION OF A PROVINCIAL STATE OF DISASTER, GAUTENG PROVINCE” of February 2017 lists damage to Station Rd, High Rd, East Rd, North Rd and Main Rd while Wood Ave gets no mention. The damage listed here was in the direct path of run-off from Meadowdale that overtopped the Buurendal attenuation dam and flowed through the suburbs.

Next step *

Wood Ave (Priority 9 in this study) certainly has risk of flooding. But the greater problem of flood risk to Edenvale suburbs of Buurendal, Highway Gardens and Hurlyvale in the path of overtopping Buurendal dam is simply missing. The flood line determination for the Eastleigh Stream needs to be done again and the priorities reviewed.

References *

Proposed Remediation & Rehabilitation of the Upper Jukskei Catchment Area, Ekurhuleni GDARD Ref. No.: 022/19-20/E0018

Fourth Element, 2017. Preliminary review of the Highveld Storm on November 9, 2016. TN/3/2017. www.fourthelement.co.za