Erosion often occurs on road embankments when there is a strong and constant impact of precipitation due to local weather phenomena. Likewise, dry periods cause the soil to hold together no longer in agglomerates due to a lack of cohesion of the soil particles but to fall apart. In the next step, high wind or water forces transport detached soil particles away. This may lead to visual obstructions due to dust accumulation or to silting and clogging by mud. If the transport forces decrease, the possibly contaminated soil material is deposited again in undesirable places. This triad of erosion, transport and deposition can lead to considerable problems.
Mechanisms of slope erosion
On slopes, surface or rill erosion usually occurs after a precipitation event has redistributed the surface. Figure 2a shows the raindrop transferring its kinetic energy to the slope surface as soon as it reaches the ground surface. In the process, the droplet disintegrates the soil particles. In Figure 2b. fine particles begin to clog the pores of the soil surface and reduce infiltration. Initial sloughing begins. Surface runoff has formed in Figure 2c. and downslope particle removal begins. Erosion, the start of the movement and subsequent transport, leads to the familiar erosion phenomena, such as erosion rills and gullies or surface erosion.
Slopes along heavily used traffic routes should be particularly protected against erosion. This is because spontaneous failure poses a risk to road users with costly consequences, e.g. expensive damage repair. Deconstruction costs can be high if deposited material impairs technical structures. It, therefore, makes sense to implement measures to reduce the erosion risk at an early stage. Thus, it is necessary to correctly understand the processes involved and develop targeted, project-specific solutions.
Figure 2: a. Erosive precipitation hits a slope surface b. Pore blockage c. Surface runoff with material transport