6.3 Dissipation block placement on the road

Check Dams and Downstream Protection In accented terrain, most streams will flow at high velocity. The development of a road section creates chutes that can cause considerable damage to the road surface and side slopes. Placing check dams in the upstream section of these road streams reduces the velocity of water crossing the road. again, spare stone material from the construction of the road may be used to build up small check dams upstream. The excess material may also be used to armor the down-road part of the stream by placing some stones there. This technique will prevent damage from erosion to the landscape and avoid upward gully development that could affect the road body. The general criteria2 for check dams are as follows:

• Spacing between check dams = height × 1.2/slope of stream in decimals • Side key of check dams, 0.7–1.0 meter each side • Bottom key and foundation, 0.5-meter deep • Height of check dams, 1 meter (maximum excluding foundation) • Stone face vertical-to-horizontal ratio, between one to three and one to five • Spillway (preferably in trapezoidal shape) width, 0.75–1.00 meter; depth or freeboard, 0.25 meter • Using rock rubble for apron immediately downstream: length 1 meter and width 0.5 meter

FIGURE 6.3

Dissipation block placement on the road

Dissipation blocks