10.3 Rolling drainage dip in low-volume road

FIGURE 10.3

Rolling drainage dip in low-volume road

Source: MetaMeta (www.roadsforwater.com). Ramp Knick

Use infiltration bunds to control erosion and enhance recharge

road runoff is a major cause of erosion and sedimentation. This flow may come from the road surface itself as well as from the surrounding area, with the road typically acting as a drain for the area around it. The volume of water conveyed from the road surface can be considerable and can cause significant erosion to the road surface and the areas adjacent to the road.

Several measures may be considered to curtail this erosion. Trees, shrubs, and grasses may be planted along rural road alignments to reduce the erosive effect of runoff from the road template. Such measures are particularly useful if no side drain is provided and the road template is outsloped or crowned. This scenario is discussed in chapter 12, which deals with roadside vegetation.

Infiltration bunds are an alternative or complement to roadside vegetation. Infiltration bunds may be more appropriate in arid areas where roadside vegetation may have difficulty taking root. Infiltration bunds can be placed on the downhill side of the road or at any other location in the catchment where they intercept sheet flow. The stone bunds disperse water and slow runoff. They ensure more infiltration of the runoff, contributing to soil moisture and groundwater recharge.

The following recommendations for infiltration bunds are based on Bender (2009). Figure 10.4 illustrates key features of these techniques.