The Proposed Flood Damage Repairs along Divisional Road (DR) 1713, De Rust, Western Cape.

Guillaume Nel Environmental Consultants (GNEC) was appointed by Western Cape Government (WCG): Department of Infrastructure for the proposed flood damage repairs along Divisional Road (DR) 1713 and associated road infrastructure, situated near De Rust in the Western Cape.

DR1713 is approximately 32.23 km in length – the road is surfaced up to km 2.39, after which it becomes a gravel road. DR1713 links to the R328 road along the west (at km 0.00 of DR1713) and to the N12 national road along the southeast (at km 32.23 of DR1713), which leads westwards to De Rust. The proposed road is situated approximately 2.9 km west of De Rust and approximately 17 km northeast of Oudtshoorn in the Westen Cape.

The primary watercourses associated with various low-level river crossings and culverts along DR1713 were the Klein-Leroux River, Groot River, Meul River, and Nels River, as well as two (2) non-perennial drainage lines (one of which is a tributary of the Groot River. Reinstating the structural integrity of the low-level river crossings and culverts are critical to ensure that the hydrological regime of the receiving freshwater environment is not altered or further impaired by water fluxes from blockages or additional sediment loads (FEN Consulting, 2025).

The proposed site constitutes the following sections along DR1713: km 0.00 to km 0.60; km 11.38; km 11.88; km 14.61; km 17.35 to km 17.60; km 18.20; and km 24.00. The proposed sections along DR1713 have been extensively damaged due to flooding that occurred during the winter months of 2024 and, thus, it is proposed that emergency repair work be undertaken along these sections of the road. Although temporary repairs were undertaken, emergency repairs are required in order to ensure road integrity and road safety through the restoration of permanent road infrastructure.

Between km 0.00 to km 0.60 of DR1713 (surfaced road), the road was completely overtopped and washed away by flooding events. Temporary repairs were undertaken to ensure that the road remains accessible to road users. Severe erosion occurred along the embankment of the road section, with the embankment being in a significant state of collapse. It is, thus, proposed that the road pavement be reconstructed and that a new open drain be constructed on the left-hand side of this road section, as well as that a reinforced concrete retaining wall with erosion protection be provided to remediate the road fill. Additionally, erosion and minor spalling of a major pipe culvert at approximately km 0.23 necessitates that erosion protection and culvert repair be undertaken.
At approximately km 11.38, km 14.61 and km 24.00 of DR1713 (gravel road), a low-level river crossing (causeway) was damaged during flooding, resulting in the causeway slab being damaged along the edges and minor scour at all ends of the structure. The causeway structure contains no guide blocks or cutoff walls, therefore, it is proposed that the existing causeway slab be overlayed and that the slab be extended on both sides with a new road slab and cutoff wall. Additionally, it is proposed that guide blocks be added and that rip rap and gabion protection be provided.
At approximately km 11.88 of DR1713 (gravel road), two (2) 900mm diameter pipe culverts have been damaged by erosion at the culvert outlets and the road embankment, with possible blockages and joint separation. Therefore, it is proposed that the culvert structures be replaced and that protection works be provided at the culvert outlets.
Between km 17.35 to km 17.60 (gravel road), severe embankment erosion of the road side drains occurred from the adjacent watercourse, which causes the side drains to be at a significant risk of collapse. It is proposed that the side drains be reinstated and provided with protection measures.
At approximately km 18.20, road fill is required due to severe embankment erosion of the road section from the adjacent watercourse, which causes the road section to be at a significant risk of collapse. Therefore, it is proposed that a gabion retaining wall with erosion protection be provided along this section.