6.9 Sheet Erosion Control and Soil
Conservation by River Bank
Protection
6.9.1 Construction of Dyke
The construction of protective dykes limits the
occurrence of flooding. Construction of dyke in
the river bank can control its erosion due to more
rigidity and diversion of river’s turbulence from
the sidewalls towards the middle. So, it reduces
pressure from river bank and the chance of erosion becomes less. Due to highly rigid guardwall by hard boulders water cannot erode it
quickly and saves the nearer villages, towns or
important places as it is done in River Manja in
North Bengal (Jha and Bairagya 2011).
This is applicable for the non-perennial rivers
of the study area like Darakeswar, KanaDarakeswar and Mundeswari (the main distributary of Damodar River) because here erosion
occurs only in rainy season and as a result proper
construction can be done in the summer only.
6.9.2 Concretization of River Bank
in Vulnerable Spots
It is very costly method but is very useful.
Occasionally, this method is used to save the
important town (Arambagh), Bigger villages
(Rajhati, Bandar, Horinkhola, Chanpadanga,
Marokhana etc.) or danger zones (Natibpur,
Dhanyagori, Sabalsinghapur, Balipur, Mohisgota, Basantabati, Bondipur, Raghunathpur) of
the study area.
6.10 Reducing Flood Levels
6.10.1 Stream Channelization
Channelization is a general term for various
modifications to stream channel itself that are
usually intended to increase the velocity of water
flow, the volume of the channel or both. These
modifications, in turn increase the discharge of
the stream and the rate and hence surplus water is
carried away. The channel can be widened or
deepened, especially where soil erosion and
subsequent sediment deposition in the stream
have partially filled in the channel. Alternatively,
a stream channel might be rerouted, for example,
by deliberately cutting off meanders to provide a
more direct path for the water flow.
6.10.2 Bypass and Channel Diversion
The construction of bypass and diversion channels is to be excavated to carry some of the
excess floodwater away from the area, which
needs to be protected. This method already
adopted in the study area. A bypass has been
constructed from Kulti to Gaighata. But the
incomplete part which will meet with Rupnarayana at Baski in Howrah district has to be
completed as soon as possible. The view of local
people is that the intensity and magnitude of
flood will probably be decreased after the completion of this Khal (bypass).
6.11 Non-Structural Measures
6.11.1 Flood Vulnerability Zoning
Floodplain zoning means restricting any human
activity in the floodplains of a river. Generally, the
term ‘floodplain’ includes water channel, flood
channel and nearby low land areas susceptible to
flooding by inundation. The zoning involves the
division of floodplain into specific zones. Zoning
is also used to restrict riverine area for particular
uses, specify where the uses may be located and
establish minimum elevation or flood-proofing
requirements for the uses. The Government of
India drafts a Flood Plain Zoning Model Bill,
1975 and the same was forwarded to the various
state Governments for necessary action.
Based on the areal extension of inundation
and flood elevation, the Darakeswar–Mundeswari Interfluve has broadly been divided into
three vulnerable zones (Table 6.9 and Fig. 6.8).
Flood Zone Mapping (FZP) and the associated zone-wise land-use regulations would be
72
N. C. Jana and S. Mandal
Conservation by River Bank
Protection
6.9.1 Construction of Dyke
The construction of protective dykes limits the
occurrence of flooding. Construction of dyke in
the river bank can control its erosion due to more
rigidity and diversion of river’s turbulence from
the sidewalls towards the middle. So, it reduces
pressure from river bank and the chance of erosion becomes less. Due to highly rigid guardwall by hard boulders water cannot erode it
quickly and saves the nearer villages, towns or
important places as it is done in River Manja in
North Bengal (Jha and Bairagya 2011).
This is applicable for the non-perennial rivers
of the study area like Darakeswar, KanaDarakeswar and Mundeswari (the main distributary of Damodar River) because here erosion
occurs only in rainy season and as a result proper
construction can be done in the summer only.
6.9.2 Concretization of River Bank
in Vulnerable Spots
It is very costly method but is very useful.
Occasionally, this method is used to save the
important town (Arambagh), Bigger villages
(Rajhati, Bandar, Horinkhola, Chanpadanga,
Marokhana etc.) or danger zones (Natibpur,
Dhanyagori, Sabalsinghapur, Balipur, Mohisgota, Basantabati, Bondipur, Raghunathpur) of
the study area.
6.10 Reducing Flood Levels
6.10.1 Stream Channelization
Channelization is a general term for various
modifications to stream channel itself that are
usually intended to increase the velocity of water
flow, the volume of the channel or both. These
modifications, in turn increase the discharge of
the stream and the rate and hence surplus water is
carried away. The channel can be widened or
deepened, especially where soil erosion and
subsequent sediment deposition in the stream
have partially filled in the channel. Alternatively,
a stream channel might be rerouted, for example,
by deliberately cutting off meanders to provide a
more direct path for the water flow.
6.10.2 Bypass and Channel Diversion
The construction of bypass and diversion channels is to be excavated to carry some of the
excess floodwater away from the area, which
needs to be protected. This method already
adopted in the study area. A bypass has been
constructed from Kulti to Gaighata. But the
incomplete part which will meet with Rupnarayana at Baski in Howrah district has to be
completed as soon as possible. The view of local
people is that the intensity and magnitude of
flood will probably be decreased after the completion of this Khal (bypass).
6.11 Non-Structural Measures
6.11.1 Flood Vulnerability Zoning
Floodplain zoning means restricting any human
activity in the floodplains of a river. Generally, the
term ‘floodplain’ includes water channel, flood
channel and nearby low land areas susceptible to
flooding by inundation. The zoning involves the
division of floodplain into specific zones. Zoning
is also used to restrict riverine area for particular
uses, specify where the uses may be located and
establish minimum elevation or flood-proofing
requirements for the uses. The Government of
India drafts a Flood Plain Zoning Model Bill,
1975 and the same was forwarded to the various
state Governments for necessary action.
Based on the areal extension of inundation
and flood elevation, the Darakeswar–Mundeswari Interfluve has broadly been divided into
three vulnerable zones (Table 6.9 and Fig. 6.8).
Flood Zone Mapping (FZP) and the associated zone-wise land-use regulations would be
72
N. C. Jana and S. Mandal