Introduction: – The flood can occur anywhere after heavy rain. Flood forecasting sufficiently in advance enables a warning to be given to the people likely to be affected and further enable authorities to take appropriate precautionary measures. It thus forms a very important and relatively inexpensive non-structural flood management measure, however, it must be realized that a flood warning is meaningful only if it is given in advance. Further erroneous warnings will cause the populace to lose confidence and faith in the system. Thus the dual requirement of reliability and advance notice is the essential ingredient of a flood forecasting system.
Current Flooding Scenario in Maharashtra
MAHARASHTRA FLOOD 2019
Multiple parts of Maharashtra were battered by heavy rains that began during the second week of August 2019. The downpour particularly affected the districts of Kolhapur, Sangli, Satara, Thane, Pune, Nashik, Palghar, Ratnagiri, Raigad and Sindhudurg.
According to a report from August 12, rain and flood-related incidents had killed 35 people across the state. As many as 761 villages were affected, and more than 4 lakh people were displaced. To conduct rescue operations, multiple teams of the National Disaster Response Force (NDRF), Navy, Coast Guard, and State Disaster Response Force (SDRF) were deployed in the affected areas.
The Warna river at Samdoli in Sangli, the Krishna at Arjunwad in Sangli, and the Krishna at Kurunwad in Kolhapur were all flowing at record levels. In fact, floodwaters in Kolhapur and Sangli only began to recede after the flood gates of the Almatti dam were opened, which subsequently led to damage in Karnataka.
(Credits: Sachin Haralkar/BCCL Mumbai)
Causes of Flooding
There are several causes of floods and they differ from region to region. The causes may vary from a rural area to an urban area. Some of the major causes of floods in India are given below.
Heavy rainfall: It is the primary cause for floods in India. Especially, rainfall in a short span of time is of much concern as they are leading to flash floods. For instance, in July 2017, Mount Abu received the heaviest rainfall in over 300 years in a span of 24 hours. The hill station received an unprecedented 700 mm of rain in 24 hours. As per a study instituted by the United Nations, climate change phenomenon is believed to be behind flash floods across the globe.
Siltation of the Rivers: Heavy siltation of the riverbed reduces the water carrying capacity of the rivers and streams leading to flooding. For instance, as a result of siltation, the Brahmaputra has been expanding – ranging from 2 km to 14 km – leading to frequent flooding in the North East region
.Blockage in the Drains: Blocked drains are the primary cause for the floods in urban areas, especially in metros. For instance, failure of the drainage system is believed to be one of the primary causes behind the Chennai floods in December 2015 that led to the death of more than 400 people.
Impact of flooding
The most important consequence of floods is the loss of life and property. Structures like houses, bridges and roads get damaged by the gushing water.
Some of the negative impacts of recurrent floods are given below –
Impact on Agriculture: Recurrent floods impact the agriculture sector adversely. Due to recurrent floods, fields get submerged and lead to the loss of harvest increasing the vulnerability of farmers to indebtedness. The loss is not only for the farming community but also the common man is hit hardly due to persistent inflation. Besides, the threat to life of milch animals impact the farming community adversely.
Moreover, floods may also affect the soil characteristics. The land may be rendered infertile due to erosion of top-layer.
Damage to infrastructure: Recurrent floods cause severe damage to economic infrastructure like transportation networks, electricity generation and distribution equipment,etc.
Outbreak of diseases: Lack of proper drinking water facilities, contamination of water (well, ground water, piped water supply) leads to outbreak of epidemics like diarrhoea, viral infection, malaria and many other infectious diseases. The probability of outbreak of diseases in highly dense areas of India is high.
Besides the above, strain on the administration, cost of rescue and rehabilitation of the flood affected population are other causes of concern.
The solution to the problem of recurrent floods lies in mitigation and rehabilitation measures. Some of the important measures are given below.
- Mapping of the flood prone areas is a primary step involved in reducing the risk of the region. Historical records give the indication of the flood inundation areas and the period of occurrence and the extent of the coverage.
- Land use control will reduce danger of life and property when waters inundate the flood plains and the coastal areas.
- The number of casualties is related to the population in the area at risk. Hence, in areas where people already have built their settlements, measures should be taken to relocate to better sites so as to reduce vulnerability.
- No major development should be permitted in the areas which are subjected to high flooding. Important facilities like hospitals, schools should be built in safe areas. In urban areas, water holding areas can be created like ponds, lakes or low-lying areas.
- The buildings should be constructed on an elevated area. If necessary build on stilts or platform.
- The amount of runoff can be decreased with the help of reforestation, protection of vegetation, clearing of debris from streams and other water holding areas, conservation of ponds and lakes etc.
- Flood diversion measures like construction of levees, embankments and dams should be undertaken.
As per an estimate, 12% of India’s land is prone to floods. As per the Central Water Commission (CWC), floods resulted in a loss of 0.86% of the total GDP. However, in the present decade, this share has come down to 0.1% of the GDP. Taking into account the growing size of the economy, still, the loss is huge. Hence the administration should take concrete measures on a long term basis to tame the menace of recurrent floods.
Keywords: – flood forecasting, flooding, rainfall, flood management, flood
NAME: – Mahesh S Waghmare
Deptt: – Department of Engineering Sciences