Detail of FLOODS , CAUSES & SOLUTION AND RIVER LINKING

FLOODS , CAUSES & SOLUTION AND RIVER LINKING

FLOODS , CAUSES & SOLUTION AND RIVER LINKING

More than 15% Rainfall deficiency throughout India and  Floods in Assam & Bihar

FLOOD

A flood is an overflow of water on land. Sometimes a river might receive extra water, either from heavy rains or other natural disasters. When this happens, the water overflows from its normal path in the river bed and onto the dry land. This is called a flood. 

Flash floods happen quickly. Extreme flooding can also be caused by a tsunami or a large storm that will cause the sea to surge inland. 

The most deadly flood was in 1931 in China and it had killed about 2,500,000 people.

Causes

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 , 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 river bed 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.

Landslides: They are the major reason behind floods in hilly areas of the north and northeast. For instance, in June 2013, landslides caused a blockage of flow of streams and rivers in Uttarakhand and caused major floods, causing 5748 deaths.

Apart from the above reasons, natural hazards like cyclones and earthquakes and encroachments of river banks and water bodies cause flooding.

Flood Control Measures and Related Problems:

The Indian government has taken various steps to check or minimise the damage caused by floods.

Storage reservoirs have been built as part of multi-purpose projects over several flood-prone rivers. Some of these reservoirs are Konar, Panchet, Maithan and Tilaiya on Damodar River, Hirakud on Mahanadi, Bhakra on Satluj, Pong on Beas, Ukai on Tapti, Nagarjuna Sagar on Krishna.

Embankments and drainage channels have been constructed to protect towns and land in flood-prone areas.

Certain long-term measures include collection of hydrological data and installation of flood warning systems. These measures, however, have their share of drawbacks and do not, in themselves, provide a comprehensive solution to the menace of flood.

Mere construction of storage reservoirs is not enough.

Extensive soil conservation measures, upstream of the reservoir and around it, are required to prevent silting of reservoirs through soil erosion. Silting reduces water holding capacity of reservoirs, thus reducing their efficiency in absorbing the overflow of flood water. According to a study, the rate of sedimentation of reservoirs in India is three times the estimated rate (i.e., estimated when they were built).

This has reduced the life of reservoirs in India to one-third. Also, in case the floods are caused by heavy rains in the downstream areas, the reservoirs are not effective. For instance, in Punjab in recent years, the Bhakra and Pong reservoirs have hardly been filled to capacity, while torrential rains caused, floods down streams, affecting nearly half the state’s population.

Embankments are not a scientific solution:

Embankments are an .unnatural way to check the flow of water. Often, the river level is above the surrounding surface in case of an embanked stream, because silt gets accumulated in the riverbed, instead of spiffing over onto the flood plain. The flood plain, as a result, is deprived of fertile silt, year after year.

Also, in case a breach occurs in a part of the embankment, the water will gush out at a very high speed and cause more damage than a slowly rising unbanked river in flood. The siltation results in floods even if there is moderate rainfall in the catchment areas. The protection provided by embankments is unstable.

Flood-Plain Zoning is a reliable and scientific method:

Compared to reservoirs and embankments, this is a ‘non-structural’ measure. This method is based on the principle that, “where the river has the right of way, stays out of its way”. Flood plain is the boundary or extent of the river movement about its mean course. Topographically, it is lower than the surrounding areas and is more prone to flooding.

Flood-plain zoning means demarcating such zones and preventing indiscriminate development and human settlement in such areas. In 1957, the Central Flood Control Board had mooted the idea of demarcating flood zones and the measures to prevent indiscriminate development and settlement in such areas. In 1975, the central government circulated a model bill containing such provisions.

It also provided for setting up of flood zoning authorities in all the states to take up surveys and demarcation of flood zones or plains. It recommended legislative support to prohibit the use of flood plains and removal of unauthorised constructions.

But most states are yet to take the desired steps under pressure from influential builders, developers and other vested interests. States, on the other hand, ask for huge funds for relief measures and not much is done for long- term protection of the flood-prone areas.

What is river linking/ Interlinking of rivers? 

·         It is a project of linking two or more rivers by establishing manually created canals, and providing land areas that otherwise does not have river water access and reducing the flow of water to sea using this means.

·         It is based on the assumption that excess water in certain rivers can be diverted to deficit rivers by establishing a channel network to interconnect the rivers Drought prone Areas of India

·         In India Interlinking of River (ILR) programme is of national importance and has been taken up on high Priority. The mission of this programme is to ensure greater equity in the distribution of water by enhancing the availability of water in drought prone and rain-fed area.

·         The Inter-link project has been split into three parts: a northern Himalayan rivers inter-link component, a southern Peninsular component and starting 2005, an intrastate rivers linking component.

·         Under the National Perspective Plan (now called the  National River Linking Project )prepared by the Ministry of Water Resources, National Water Development Agency (NWDA) has already identified 14 links under Himalayan Rivers Component and 16 links under Peninsular Rivers Component for inter basin transfer of water based on field surveys and investigation and detailed studies.

·         Out of these, Feasibility Reports of 14 links under Peninsular Component and 2 links (Indian portion) under Himalayan Component have been prepared. Draft Feasibility Reports of 7 link projects (Indian portion) of Himalayan Component  have also been completed

Flood prone areas of India

Various plans on River Linking in India

Organisations for River linking

The river linking project is being managed by India’s National Water Development Agency (NWDA), under its Ministry of Water Resources. 

Advantages of River Linking  

·         Hydropower generation: The river interlinking project claims to generate total power of 34,000 MW (34 GW). Out of this, 4,000 MW will come from the peninsular component while 30,000 MW from the Himalayan component.

·         Curb drinking water woes: The addition of hydropower is expected to curb the drinking water woes of millions and supply water to industries in drought-prone and water-scarce cities in south and west India

·         Irrigation: The river linking project claims to provide additional irrigation to 35 million hectares (m ha) in the water-scarce western and peninsular regions. 

·         Employment and Agriculture: In addition to irrigation the project will further create employment, boost crop outputs and farm incomes and multiply benefits through backward (farm equipment and input supplies) and forward linkages (agro-processing industries). It may even help for fishing.

Disadvantages of River Linking 

·         Costs:  The money planned to be spent on the river linking project is not economically feasible to a country like India

·         Environmental: The environmentalists challenge that the project lacks holistic assessment of socio-economic impacts such as water-logging, salinisation and desertification. For example the Ken-betwa river link project resulted in felling of more than 1.8 million trees and also affected the Panna Tiger Reserve.

·         States acceptance: Many of the states are not fully agreed with the river linking project as it may lead to the shortage of water to upper basin state

·         Displacement of people: For the completion of Interlinking River project, many big dams, canals and reservoirs will have to be constructed due to which people around the land will be displaced.

Recent linking of rivers

Ken Betwa link project

·         It aims to link the rivers of Ken and Betwa and transfer the surplus water from Ken river to the betwa river through a canal to irrigate the Bundelkhand region and it would benefit both Uttar Pradesh and madhya Pradesh in terms of meeting irrigation drinking water and electricity needs of people across 6 districts in the two states

·         Ken-Betwa link project has been declared as a National Project by the Government of India

·         It has received clearance from the Supreme Court of India, The National Board for Wildlife (NBWL) and the Environmental clearance

Other projects under pipeline

Damanganga-Pinjal Link Project and Par-Tapi-Narmada Link Project 

·         Both of them are twin links concerning Maharashtra and Gujarat. Damanganga-Pinjal Link Project benefits Maharashtra while Par-Tapi-Narmada Link Project benefits Gujarat. The Detailed Project Reports of both links are ready. Central Water Commission has completed techno-economic appraisal of Damanganga-Pinjal Link Project while the techno-economic appraisal of Par-Tapi-Narmada Link Project is in advance stage. 

·         Both the governments of Maharashtra and Gujarat have finalized the MoU regarding the project

Godavari-Cauvery(Grand Anicut) link project

·         Pending consensus on Mahanadi-Godavari and Godavari(Inchampalli)-Krishna link projects due to large submergence involved, alternative studies have been carried out to divert unutilized water share of Chhattisgarh State in Indravati sub-basin in  Godavari basin (as per GWDT award) to Cauvery through Godavari-Cauvery link project. Technical Feasibility Note for this proposal was prepared and sent to party states in 2017

Global examples of interlinking of rivers

1.    Rhine-Main-Danube canal

2.    Illinois Waterway system

3.    Tennessee–Tombigbee Waterway(USA)

4.    Gulf Intracoastal Waterway(USA)

5.    Dian Zhong Water Diversion Project(China)

6.    Murray–Darling basin(Australia)