Preventive measures which aim at reducing the frequency / intensity and impact of floods can be classified as Structural and Non-structural measures.
Structural Measures include
- Dams and Reservoirs
- Detention Basins
- Channel improvement
Non-structural measures include
- Flood plain management such as flood plain zoning
- Flood forecasting and warning
- Disaster management
- Flood fighting including Public Health Measures
- Flood insurance
The most common structural measure in use to counter floods in the region is embankments. Altogether more than 3400 km embankments exist along different rivers in Bihar. In the focus area main rivers are mostly embanked. River Burhi-Gandak is embanked except in the upper reaches. Bagmati is embanked from Dheng bridge to Runnisaidpur and the from Hayaghat to Badalaghat. Khiroi, an important tributary of Bagmati is also embanked. Darbhanga-Bagmati is embanked on left bank in the vicinity of Darbhanga town. Kamala is embanked up to Darjiya. River Kosi is also embanked on both sides. These embankments have seized the wide range migrations of rivers. However, these embankments have some gaps which reduce its effectiveness.
The area has a number of depressions locally called Chaurs. These Chaurs naturally act as detention basins. It is supposed that the Chaurs absorb a considerable amount of water of the first flood of the season. No man made detention basins or improvement in the natural Chaurs to enhance their utility is learnt to be in practice. Channel improvement is also not a usual practice.
Flood forecasting for certain points along rivers are being done by CWC since long. Those forecasts have been used by the concerned departments for issuing warning when required. Improved flood forecasting with increased lead time and accuracy is one of the main objectives of FMIS, Bihar.