FIGURE 9.2
Source: MetaMeta (www.roadsforwater.com).
Unprotected river bank River bank erosion due to lack of protection by riprap or vegetation
Road approach
End failure Peak floods rise above level of concrete road surface and erode drift road approaches
Apron
Direction of flow
Top slab failure Poor construction method and poor materials result in cracks to head wall or drift slab
Concrete road surface
Under-scouring Lack of apron/inadequate apron results in underscouring of the drift foundation
Drift failure mechanism
Overview of nonvented drift with preventable failure features
Seasonal sandy river
Unstable fill materials Insufficient or unsuitable material results in damage of top slab due to traffic loading
Lack of robustness Lack of rigidity results in damage by floodwater when it enters into the structure
Road approach
154 | Green Roads for Water
