Most states are facing floods. The immediate reason for this is global warming. The rainfall, which fell in three months earlier, is now falling in less number of days due to which the water in the rivers increases abruptly. The river is not able to carry the sudden inflow of water and it takes the form of flood. Due to this change in the pattern of rainfall, we have to increase the capacity of rivers to carry the water to the Sea. Only then the floods will decrease. Instead, we are decreasing the capacity of the river to carry flood waters. In this post, we will try to show how floods in Kerala were caused by encroachment in the riverbeds.
Obstruction by Bridges
We give below picture of the bridge built over the Pattambi River in Figure 1 below. The water is stagnant on the right side of the bridge. It has become a pond.
Whereas, on the left side we can see that the water is flowing fast. Thus, this bridge is making an obstruction to the flow of river. Due to this barrier, the water level of the river is increasing in the upper area, which is causing flood.
Similarly, we can see below in Figure 2 that water is flowing above the road on the Karuvnnur River in Thrissur district because of inadequate provision for the flow of river water. Due to this, the water level has increased in the upper part of the river and become a flood.
The river needs chance to spread. Generally the riverbed is in the shape of "V". As the water level of the river increases, the cross-section area of the river also increases and the capacity of the river to carry water also increases. But we have changed the shape of the river from "V" to "U" by constructing residential houses along the riverbed.
We can see the rest house on the bank of the Periyar River in Idukki district in Image 3 below. This has reduced the cross section of the riverbed due to which the water has spread over large area.
Similarly in Figure 4 below, large buildings have been built on the river bank in Chalkka city of Ernakulam district. Due to which the cross section of the riverbed has reduced.
There are more than 35 hydropower projects in Kerala. A barrage is built for diverting river water for turbine operation. These barrages become barrier for river water flow when heavy flood comes. We can see in Figure 5 below that the barrage built in Mullaperiyar hydropower project has created such an obstruction.
In Kerala, the use of lands on the bank of the rivers is being used for cultivation. We can see in Figure 6 that the path of Payaswini River in Kasargod district has been blocked by constructing soil wall to divert water for irrigation. Thus the river cannot carry more water when the rainfall is high.
The people of Kerala have encroached the riverbed due to these human activities. Already global warming has increased the likelihood of floods and by reducing the number of days in which the rain falls. The recent floods have killed more than 300 people in Kerala because of this reduction in the flow of the free flowing rivers. The loss from the floods may be much more than the benefits from bridges, hydropower projects, irrigation and expansion of the residential areas. Therefore, the Government should take steps to preserve the riverbeds in entire country.