In This article I am going to show you about Solutions to flooding, Flood Mitigation Measures as per field condition, bank condition availability of fund and economically viable acceptable to the community and community-based structures. It includes engineering and structural and bio-engineering works.

Project Components



In order to undertake the flood mitigation project in a practical and sustainable manner, it is important to implement the measures in combination with community development activities. The flood mitigation efforts are thus divided into two components as structural and non-structural, which must be practiced in parallels during flood mitigation works.

Non-structural Measure

Measure to reduce loss or damage by administrative measures. It does not control or affect the process of inundation. It does not foster any economic growth must be linked up with structural measures and vice-versa.

Structural solutions to flooding

A measure to control the physical process of flooding, and is solutions to flooding, It also prevents inundation, protects vulnerable areas up-to a certain level of flooding. Structural measures with adequate appurtenant structures and proper water management practices create a condition for increasing productivity from land and other developmental activities.

Some structural measures planned to undertake flood mitigation in a practical and sustainable manner are:

Embankment

Embankment with Revetment and launching apron Toe wall (Vertical revetment and river bank strengthening work) Earthen Embankment

Spur and stud

Gabion box with stone filling bamboo stud, Spur

Drain Outlet Structure

Emergency River Training work

River Channelization

Bio-Engineering work

a) Bank Protection (Embankment)

Embankment in both banks with revetments and without revetments or simple earthen embankments are proposed in this report. The purpose of bank protection is to protect the banks from erosion, vertical cuttings of the banks and accordingly to stabilize the river course.This work aims to prevent floodwater and sediment from spilling over the banks. Grass and trees planted on the riverbanks resist and retard the erosion. For this bio-engineering technology can be used as preventive measures against bank erosion. Two types of embankment are proposed in this study.

Embankment with Revetment and launching apron

Earthen Embankment

b) Spurs or Groynes works

A series of spurs prevent bank erosion primarily by two functions of the spur, namely, to retard flow velocity near the bank and to change the flow direction away from the bank.

This prevents bank erosion by converting bank slopes and protecting their foundations. Spur and stud are constructed with gabion mesh wired boxes with filling stone in it and somewhere bamboo stud and spur can be constructed for a low-cost approach as required.

Fig3. Embankment with Revetment

c) Drain Outlet Structure

It is desired to exit local drain safely to the main river, to eliminate flood inundation in the countryside (village, cultivated field). Drain outlet can be done using Hume pipe crossing or box culvert throughout the cross embankment. Size of outlet depends on the catchment size, drainage pattern, surface, and rainfall intensity.

d) Canal Off-taking Structure

There is several canal off-taking structures built over several decades, some are running properly. This structure is provided as an inlet of canal head or canal side intake structure. Size of inlet structure depends upon the cultivated land area and duty of canal feed, Just reverse direction of drain outlet structure.

e) Emergency River Training work

This provision is made to combat the emergency period of flooding period. Recover work for post and pre-stage of the emergency period is desired additional flood mitigation work, where the flood outflanked, bank erosion, as well as course shifting tendency of the river, will be occurred.

f) River Channelization

To reduce the length of the embankment and recovered more land area as well as the desired shape of the river to be established, some length of river can be channelized, if possible or there will not any conflict. So this work can be done as per the people’s demand if the channelization work is technically feasible, economically viable and socially acceptable.

Fig4. A community affected by Flood

g) Bio-engineering

Bioengineering or vegetative engineering is an “engineered” combination of vegetation used for the stabilization of riverbanks to reduce the erosion in the flood-prone area and is a solution to flooding. It is an effective low- cost measure for flood control project. The vegetative or bioengineering techniques may be tree & shrub planting, grass seeding, tree & shrub seeding, bamboo planting, turfing, vegetated rip-rap, vegetated gabions, and many others.

Bioengineering system work by fulfilling the engineering functions required for the protection and stabilization of riverbank slopes. The bio-engineering works with civil structures and without civil structures (only vegetation) fulfill one or more or the roles of catching debris, armoring the surface, reinforcing the soil, anchoring the surface layer, supporting the slope etc.

But it should not forget that degree of fulfillment of these above engineering function depends upon the type of plants and methodology used in bioengineering works. Normally it is recommended to use the species, like Amriso, Babiyo, Dhonde, Dubeo, Kans, Khar, Khus, in the riverbank slope depending upon the site condition. Similarly, in the riverbank slope and in the flood-prone area, Bakaino, Khayer, Setosirisetc is recommended to plant in the flood-prone area.

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