Various causes of flood
1. Heavy rainfall
Whenever there is heavy rain and the drainage system is not proper, it may result in a flood or flood-like conditions.
2. Topography of the catchment
- The size, slope and shape of the catchment area directly affects the flow of the river.
- It is obvious that larger the size of the catchment more will be the flood.
- The catchment area with steep slope increases the run-off and increases the sediment inflow due to the high velocity of flow.
- The shape of the basin also definitely affects floods.
3. Obstruction in the river flow
Sometimes, due to heavy landslides in the river, the natural flow of water is obstructed resulting in flood situation on the upstream of the river. When the obstruction in the river are removed due to heavy water pressure accumulated on the upstream, flooding is caused on the downstream of the river.
4. Failure of dam
Dams are designed to hold water upstream. If the dams begin to collapse, they will discharge more water downstream, resulting in flooding. That can cause more problems for people living in the low-lying areas around the dams. It may also result in deaths.
5. Lack of vegetation
Vegetation can interrupt the flow of water. If there will be no vegetation, there will be nothing to slow down the flow of water.
6. Inadequate cross drainage works
Sometimes at the crossing of canal and river, it may be required to pass the river below the canal, by constructing a aqueduct. Due to the construction of an aqueduct, the depth of flow is reduced. Thus, during high flood, water level may rise on the u/s side and may submerge the surrounding area.
7. Sedimentation of rivers and reservoirs
If the tributaries of a river carry heavy sediment load the river bed goes on silting up gradually every year. It will affect the carrying capacity of the river. Ultimately the cross-section of the river will be shallow and it will not be able to carry the high flood flow. Thus sedimentation of rivers and reservoir are also responsible for the flood.
