Patna, June 20: India Meteorological Department (IMD), Patna, today started to issue floods forecast for river catchments in the state, a day after the arrival of monsoon.

“After the arrival of monsoon in the state yesterday, Flood Meteorological Office (FMO), Patna, has started operating today. The FMO provides flood forecasts, according to the amount of rainfall, for various rivers passing through the state, including Kosi, Kamala, Gandak, Bagmati and Punpun. The forecasts will be issued daily till the end of monsoon in September,” said Ashish Sen, director (radar), IMD, Patna.

The daily rainfall data are provided to Central Water Commission (CWC), Patna, which in turn, estimates the rise in the water level in the rivers. The CWC then informs district administrations concerned about the rising water level and accordingly flood alerts are issued.

Experts claim that flood forecasts are very important for Bihar where over 40 per cent of the total geographical area is classified as flood-prone zones.

“There are 17 streams in the Himalayan region that cross the international border with Nepal and enter Bihar. The sediment load of the rivers flowing through the state is very high. The force of the water, as the rivers approach plain land, reduces and the sediment load becomes silt,” said M.B. Verma, a retired scientist of the Defence Research and Development Organisation and a resident of Darbhanga.

Explaining the cause of frequent floods in the state, Verma added: “The silting reduces the area of the river channel. This causes the river to overflow the banks and leads to floods. Over 40 per cent area in the state is susceptible to such floods.”

Sources said when the rainfall forecast is between 0.1mm and 10mm the water level in the rivers rises by 1m. But if more rainfall is recorded between 51mm and 100mm, the water level in the flood-prone areas can rise by 5m.

Authorities claim that sufficient precautionary steps have been taken to prevent floods as well as mitigate disasters.

“The state water resources department has made arrangements for all-round patrolling along 3,615km of river catchments areas in the state. Homeguard jawans have been deployed at every 2km along river embankments. We have also identified several flood-sensitive points, where special vigil is being kept. The department has also constituted 12 flood-fighting forces, comprising a retired chief or superintending engineer as the chairperson, and executive assistant and junior engineers as its members. Each force also has an official from the disaster management department and a section of armed forces,” said Shubh Chandra Jha, public relation officer, water resources department.

Experts claimed it is important to distinguish between a flood and an avulsion. Rajiv Sinha, a teacher of geosciences, department of civil engineering, IIT Kanpur, said an avulsion is defined as a sudden change in the course of a river. Flood occurs due to heavy rainfall.

The Kosi disaster of August 2008 has been described as an avulsion because of a breach in the embankment of the river at Kusaha in Nepal.