Table 5 Current physical safety problems associated with the ten dams surveyed

Note: * On the basis of ten dams

Dam components Actual problems Details of problems Percentage of dams*
Reservoir Inability to store design water capacity Sediment accumulation; Irrigation gate leakage; Spillway leakage 100%
Crest Overtopping Inaccurate estimation of hydrographical parameters; Spillway is blocked; Flooding is over the design flood capacity; The top is constructed lower than designed 60%
Settlement on the crest Traffic damage; Animal burrowing activities; Instability of the embankment 80%
Transverse cracking The dam foundation is depressed; Instability of the embankment; Shrinkage of surface materials; Materials are low quality 20%
Longitudinal cracking Water in the reservoir increases or decreases suddenly. This sudden change of water level creates depression on the top; The dam foundation is depressed; Slide occurs on the embankment 40%
Ruts along the crest Traffic damage; The movement of foundation 30%
Upstream slope Seepage under the foundation The quality of material is low. Hence, water is eroding the material; Rodent activity; Geological assessment is inaccurate 20%
Slide and slump The lack or loss of embankment material; Rodent activity; Erosion; Traffic damage; Downstream slope is too steep 80%
Sinkholes The movement of foundation create holes; Material is seeped; Animal burrows 20%
Downstream slope Seepage through the embankment Rodent activity creates open pathway through embankment; The abutment is not properly designed and constructed 70%
Seepage at the abutment The abutment is not properly designed and constructed; Plants/trees are not removed completely in construction 30%
Slide and slump The lack of or loss of embankment material; Rodent activity; The downstream slope is too steep 80%
Spillway Eroded spillway Erosion; The gradient of the channel is too steep 20%
Blocked spillway Soil and stone erosion; Trees and plants; Inaccurate design 50%
Outlet Eroded outlet Outlet is too small; Conduit is eroded; Foundation movement 20%
Leaking and breaking Valve is broken; Vandalism; Outlet is too old 40%