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Initial Environmental Evaluation, Northeast Regional Water Management Plan, Bangladesh Flood Action Plan 6

CHAPTER 9: ASSESSMENT OF REGIONAL PLAN IMPACTS

9.1  INTRODUCTION

This chapter describes the expected impacts of implementation of the Regional Plan.

The residual impacts of Plan implementation represent the sum total of numerous factors:
 

A. Direct impacts of flood control and drainage measures
B. Mitigating/compensating impacts of mitigation/compensation measures incorporated into individual FCD projects
C. Direct impacts of non-FCD projects
D. Cumulative impacts of FCD projects
E. Interactions among FCD projects (project-on-project impacts)
F. Environment-on-project impacts
G. Mitigation and compensation of adverse FCD impacts by non-FCD projects

 

 
 
 

Impacts in categories A, B, and C are documented in individual project pre-feasibility studies. Quantifiable impact indicators from these studies are tabulated and totalled in Table 9.1 and Figure 13.

Impacts in categories D through G, are documented in Sections 9.2 to 9.5 of this chapter.

Expected residual impacts are then described in Section 9.6. The implications of partially or differently-phased implementation of the Plan are discussed in Section 9.7. Impacts are characterized for each subregion in Section 9.8.

Mitigation measures are summarized in Section 11.2.

9.2  INTERNAL CUMULATIVE IMPACTS OF PLAN INTERVENTIONS

9.2.1  Interpretive Description of Cumulative Physical Impacts
The initiatives which will produce the greatest physical impacts in the region fall into three broad categories:

Controlled flooding (full flood control with controlled flushing) and partial flood control projects along the Surma-Baulai and Kushiyara-Kalni Rivers which extend from Amalshid on the east to near the outlet of the Central Basin in the southwest (Upper Surma-Kushiyara Project, Surma Right Bank Project, Surma-Kushiyara-Baulai Basin Project).

Major drainage improvement schemes along the lower reaches of the Kalni and Baulai River systems (Kalni-Kushiyara River Improvement Project, Baulai River Improvement Project)

Controlled flooding projects on the piedmont rivers (Manu, Bhogai-Kangsha) which involve either flood control embankments or flow diversions (Manu River Improvement Project, Upper Kangsha River Basin Development Project, Habiganj-Khowai Area Development Project).

Spills of water and sediment to the low-lying Surma-Kushiyara inter-basin will be reduced by construction of the Upper Kushiyara Project. Right bank spills from near the Lubha River will be eliminated by the Surma Right Bank Project. This will increase in-channel discharges and water levels along reaches of the Surma and Kushiyara during the monsoon season. The greatest impacts will occur near Kanaighat, where monsoon flood levels will rise by approximately 0.6 m after breaches at the existing embankment are closed (Regional Plan Figure 21B). Further downstream, regional surface water model results showed monsoon flood levels will rise by on the order of 0.2 m from Sylhet to Sunamganj, and will be virtually unchanged downstream of the Old Surma River junction (near Nilpur). Model simulations indicated water levels will rise by generally 0.5 m or less on the Kushiyara upstream of Sherpur during the monsoon season. Rates of channel migration and bank erosion will be increased along the upper Surma and upper Kushiyara and some channel degradation may be expected.

Spills will also be reduced into the Central Basin after completion of the Surma-Kushiyara-Baulai Basin Project and the Kushiyara-Bijna Interbasin Project. Sedimentation rates in this main haor area will decline due to the reduced inflows. Re-excavation of the interior drainage network (such as Old Surma River and Darain River) will result in some local erosion/deposition.

Construction of partial and full flood control embankments will increase in-channel discharges slightly along the Baulai and lower Kushiyara-Kalni Rivers during the monsoon season. The increased confinement will tend to raise monsoon flood levels (particularly on the Kalni River where submersible embankments will approach the level of an average monsoon flood). This confinement will be offset by other dredging initiatives. Confinement will also increase the channels' sediment transport capacity which will flush more of the incoming sediment load through the Kalni into the upper Meghna and more sediment from the upper Baulai into the lower Baulai-Ghorautra system.

River improvement initiatives along the Kalni-Kushiyara and Baulai will reduce the variability of depths and will produce a more uniform, incised single channel pattern. Spoil from dredging may raise ground levels on the floodplain or in side channels and beels. Associated river training works will produce local scour and erosion at shoals and in constricted reaches so that considerable local channel re-organization can be anticipated. Pre-monsoon and post-monsoon water levels will be lowered in the dredged reaches and upstream. As shown in Regional Plan Figure 21A, water levels at Markuli will be reduced by as much as 1.5 m during the winter and pre-monsoon periods. Monsoon peak water levels will be reduced by 0.1 m to 0.2 m, while the channel discharge will be increased by as much as one-third. Dredging on the Baulai was found to have less impact, with pre-monsoon water levels lowered by 0.2 m and post-monsoon water levels lowered by 0.5 m. It should be noted that water levels and discharges at Bhairab Bazar on the Meghna were not impacted by these initiatives.

Dredging of the Kalni and Baulai appears to mitigate the effect of higher discharges in the post-monsoon season due to Tipaimukh Dam. Actual impacts would have differed if other upstream dam/irrigation scenarios had been adopted in the simulations. The model results clearly illustrate that upstream flow regulation of the Barak River in India will have a major impact on the Northeast Region. Therefore, scheduling of some initiatives along the Surma and Kushiyara Rivers will have to fully consider future developments in the Barak River basin.

The Manu River Improvement Project will divert a portion of flood flows into Hakaluki Haor to reduce discharges at Moulvibazar. This will alter the regime of both the Manu River and the area around Hakaluki Haor. Sediment deposition may occur on the Manu River below the diversion since the river's sediment transport capacity will be reduced. The diversion flows will also produce sediment deposition in Hakaluki Haor. This deposition will occur by development of a delta into the haor and by channel switching across the low-lying land. Rapid sedimentation is expected when the diversion is operating.

Major impacts to water levels, discharges, and channel regime are also anticipated due to the construction of embankments and the flow diversion associated with the Upper Kangsha River Basin Development. Full flood control embankments will reduce spills along the Kangsha River and will produce higher in-channel discharges. Model simulations indicated peak water levels could be raised by more than 1 m at Sarchapur bridge and that impacts will extend as far downstream as Jaria Janjail (Regional Plan Figure 21B). Water levels and flows were also forecast to increase on the Kangsha between Jaria Janjail and Mohanganj due to closure of the Atrakhali spill channel. This will flush more sediment into the lower Kangsha River and will contribute to infilling of the dredged reach along the Baulai River.

A second component of Upper Kangsha River Basin Development Project involves diverting some flows from the Chillikhali and Malijhee Rivers through an excavated channel into the upper Mogra River. This diversion will increase the discharge on the Mogra River and may increase flood stages at Netrokona. Actual water level changes at Netrokona were found to be very sensitive to the assumed project layout so additional analysis will be required to firmly establish these impacts. The increased discharges could lead to some enlargement of the Mogra River by channel erosion and degradation. The increased flows will also flush fine sediment into the Dhanu-Baulai River system.

9.2.2  Regional Surface Water Model Results by River System
Upper Meghna
At Bhairab Bazar, regional surface water model water levels were unchanged from the FWO simulation.
Kushiyara River
Upstream of Sherpur, model water levels increased 0.5 m or less as a result of embankments and channel closures which confine flows in the Kushiyara by reducing spills onto the Kushiyara floodplain. Further downstream, model winter and pre-monsoon water levels at Markuli decreased by 1.5 m, as a result of Kalni-Kushiyara River improvement (Regional Plan Figure 21A).
Surma River
The situation in the Surma is similar to that in the Kushiyara. Near Kanaighat, model water levels increased 0.6 m as a result of embankments and channel closures above this point. Working downstream, from Sylhet to Sunamganj, model water levels increased 0.2 m; at Nilpur, no change occurred; at Sukdevpur, model water levels were unchanged or slightly lower but discharges increased, reflecting the impacts of Baulai River improvement. At the lower end, model winter water levels decreased by 0.5 m, and pre-monsoon levels decreased by 0.2 m.
Kangsha River
In the reach upstream of Jaria Janjail, model water levels increased as a result of the confinement of the lower Bhogai and upper Kangsha; Sarchapur water levels increased by 1.5 m. Between Jaria Janjail to Mohanganj, model water levels increased 0.5 m as a result of the closure of the Shibganjdhala; this represents a return, approximately, to current conditions.
Mogra River
In the Mogra, model discharges and water levels increased significantly as a result of works on the upper Kangsha which would divert Chillikhali River and Malijhee River flows into the Mogra. This result is however highly dependent on details of the simulation and further investigation is required.
Khowai River
In the Khowai, model flood peaks increased by 200 m3 s-1, reflecting the net result of decreased spills from the Khowai into the Karangi River, and diversion of flows from part of the Khowai basin into the Sutang River. This is a preliminary result and further investigation is required for design purposes.
Jadukata River and Patnaigang
With closure of the Patnaigang, model Jadukata flows, especially in the post-monsoon and winter periods, increased at the expense of model Patnaigang flows.

9.3  INTERACTIONS AMONG FCD PROJECTS

Figure 14 shows a screening matrix of project interactions. This plot identifies projects which will produce impacts on other initiatives, as well as those projects which will receive impacts. Project interactions have been classified according to their expected magnitude using a simple ranking, with A representing the strongest interactions and C representing minor or no interaction. Cumulative scores of provide a crude means of ranking projects that have the greatest overall impact to the development plans in the region as well as identifying projects that will be highly sensitive to other initiatives. Impacts have been assessed for the future condition (2015) with the assumption that Tipaimukh Dam will be constructed. Therefore, in terms of long-term interactions, the initial phasing of individual projects is not very critical.

Projects which have either no interactions or only a minor interaction with a single other project were treated as essentially independent initiatives. These projects include:
 

Mrigi Drainage Improvement
Upper Kangsha Project
Narayanganj-Narsingdi Project
Narsingdi District Project
Manu River Project
Habiganj-Khowai Project
Sarigoyain-Piyain Project

9.4  ENVIRONMENT-ON-PROJECT IMPACTS

9.4.1  Introduction
9.4.2  Usual and Customary Events (Current Conditions)
Usual and customary events which cause environment-on-project impacts include erosion of embankments and homestead platforms by river and floodplain flows and by wind-generated waves. The intensity of this erosion is a key determinant of maintenance and rehabilitation requirements. If maintenance is inadequate, embankments will breach, greatly multiplying the infrastructure damage, and homestead erosion will accelerate with decreasing platform heights and increasing frequency of inundation.

Historically, public cuts have been a common occurrence in the region. In some cases, these amount to a rational (if illegal), low-technology, locally-controlled, inexpensive means of water management, with local farmer groups working together to cut an embankment for local drainage and then repairing it to prevent flood inflows, sometimes over a series of years. It is to be expected that such activities will continue in the future, and it would be desirable for environmental/water resources management systems to develop capabilities for monitoring, evaluating, and where needed negotiating modifications to them.

The case of public cuts undertaken at times of crisis are discussed below in Section 9.4.4.

9.4.3  Trends (Future Conditions)
Future trends which could contribute to environment-on-project impacts are:
  • Tipaimukh Dam -- reservoir filling and operation. Included in the FWO scenario (Section 8.3.2). Further environment-on-project/Plan impacts discussed in Section 9.7.1.
  • Increased rainfall and rainfall variability (climate change) and increased flood levels and discharges (cumulative effects of infrastructure development + climate change). Environment-on-project/Plan impacts discussed in Section 10.1.5.
  • Changes in upland land use. Upland deforestation in the smaller river basins associated with the alluvial fan and piedmont river basin areas may increase runoff and sediment inputs in these systems. Significant effects on the main river systems (Kangsha, Surma/Kushiyara, Meghna) are not expected because of the sediment and runoff buffering effects of headwater systems.
  • Population growth, urbanization, industrialization leading to increased pressure on and social conflicts over biophysical resources and increased water contamination.
9.4.4  Hazards
The region's water systems and Plan projects are vulnerable to:
  • Earthquake. Impacts on Plan projects would be similar to impacts on existing infrastructure and other systems. These are discussed in Section 8.8.1.
  • Catastrophic flash floods on the Meghalaya and Piedmont rivers. Discussed in Section 8.8.3.
  • Tipaimukh dam failure. This would completely overwhelm existing and proposed infrastructure and other systems. Discussed in Section 8.8.2.
  • Public cuts in response to flooding, conflicts between interested parties, and as sabotage (for political or personal reasons) or vandalism. Such cuts can cause massive flows and inundation, and infrastructure damage. Anticipatory planning based on extensive public consultation can minimize but probably not eliminate risks.

9.5  MITIGATION, COMPENSATION, AND ENHANCEMENT OF FCD IMPACTS BY NON-FCD PROJECTS

The Plan portfolio includes several projects which would mitigate, compensate, or enhance impacts of Plan FCD projects. This type of mitigation, compensation, and enhancement is in addition to mitigation, compensation, and enhancement measures incorporated within individual Plan FCD projects.

Under the Fisheries Engineering Project, an attempt would be made to develop fish passes to mitigate fish migration impacts of embankments, closures, and water control structures. Other structural measures would protect beels from sedimentation and increase dry season water storage.

Under the Fisheries Management Programme, biological management of the floodplain fishery would be improved through interventions in fisheries habitats, assistance to New Fisheries Management Policy (NFMP) fishermen associations, and improvements in management of small community fisheries (mohalshamil jalkar, <1.2 ha in area).

Under the Northeast Region Environment Management Research and Education Project, which is composed of 11 of the 44 initiatives proposed in the Plan, measures would be undertaken to preserve and enhance regional biodiversity and to improve the management of regional surface water quality, through measures in the field and through institutional strengthening. These measures compensate in part for adverse impacts of Plan FCD projects in these areas.

Ground Water Investigation addresses ground water management issues. The direct impacts of Plan FCD projects on ground water abstraction are very slight, but they may in some areas contribute to over-exploitation.

Dredging for Navigation and Support to Country Boats would act synergistically with the major river improvement (drainage improvement) projects to enhance navigation.

9.6  RESIDUAL PLAN IMPACTS

9.6.1  Biophysical Impacts (FCD and non-FCD) by Environmental Component
Displacement impacts
FCD projects.  Project physical works (embankments, structures, and larger channels) would displace cultivation and settlement (homesteads) on a total of 3,000 and 400 ha respectively in the region. This would be 0.2% and 0.9% of total cultivated and settlement areas within project areas. Lost agricultural production from these cultivated and homestead areas is included in the Agriculture section below. The population displaced from settlement areas is discussed in Section 9.6.2, Socioeconomic Impacts.

Other projects.  Displacement of FWO land usage on very small areas could occur in the construction of wetlands or other facilities for wastewater treatment, and in the Bhairab Bazar Erosion Protection Project (see box). There would be no displacement impacts from any of the other non-FCD projects.

Settlement and road impacts
FCD projects.  A total of 6,400 ha of settlement area (homesteads) would be protected from flood damage (nominal 1:10 return period). This would be 9.7% of the total regional homestead area of 65,000 ha, and 52% of the 12,000 ha of FWO flood-affected homestead area within project areas. Proportionate numbers of people (rural population) would be protected; this is covered in Section 9.6.2, Socioeconomic Impacts.

Spoil from manual excavation and dredging could be used to create new and raise existing homesteads on 740 ha.

Flood damage to urban centres would be reduced in four of the eight major urban centres (Narsingdi, Narayanganj, Habiganj, Moulvibazar) and fourteen of the 74 thana centres. Patterns of future development, and effectiveness of future flood-zoning efforts, will greatly influence the functional future impact (population and urban infrastructure protected) of the urban flood protection provided. Urban population protected is discussed in Section 9.6.2, Socioeconomic Impacts.

Flood damage to roads would be reduced. Assuming that future and existing road networks would be the same, in the absence of site information for future additional roads, there would be 3600 km of roads within projects' gross areas; of which 1,600 (45%) would be FWO flood-affected; of which 580 km (16%) would benefit from flood protection.

Other projects - rural settlements.  Rural settlements' biophysical environment would be positively impacted by a number of projects (see box).  There would be no negative impacts on rural settlements from non-FCD projects.

Other projects - urban settlements.  Urban settlements' biophysical environment would be benefitted by a number of projects (see box).  The Urban Potable Water Project has the potential for adverse biophysical impact, since it would greatly increase the volume of urban domestic wastewater. Urban wastewater treatment is addressed by the initiative Duckweed-Based Wastewater Treatment. There would be no negative impacts on urban settlements from any of the other non-FCD projects.

Other projects - roads etc. With the exception of erosion protection in the Bhairab Town Erosion Protection project, road impacts would be nil.

Agricultural impacts
FCD projects.  Annual regional paddy and other grain production would increase by 570,000 tonnes, or 10% of the present production of 5.6 million tonnes. Rice-cropped area would increase by 38,000 ha, or 2.0% of the present area of 1.9 million ha. Flood (again, 1:10 year) damage to crops would be reduced on 320,000 ha. The incremental rice area and annual rice production given here reflects 12,000 tonnes of lost annual production on 5,200 ha of farmland that would be converted to other land uses:
  • Up to 700 ha converted to homestead use by spoil deposition to create new homestead platforms;
  • 1,500 ha converted to channel area as a result of re-excavation; and
  • 3,000 ha converted to embankments and other project infrastructure.
This is a maximal estimate of the adverse impact on agricultural land use, in that it is assumed that the area to be converted to channels is 100% under rice cultivation and already owned by BWDB (i.e. all acquired land to be used for embankments and other project infrastructure). In fact, not all land along channels is cultivated, not all cultivated land is under rice, and some acquired land would be used for channel re-excavation.

Annual regional production of other food crops would increase by 123,000 tonnes, or about 12% of the present production of 1.0 million tonnes; this includes all non-grain crops except sugar cane, excluded on account of its anomalously high mass yield per hectare and low nutritional and economic value per unit mass. Other-food-crops cropped area would increase by 68,000 ha, or about 20% of the present area of 340,000 ha.

Crop diversity as represented by the ratio of other-food-crop to rice production by mass, would increase slightly from 0.183 to 0.186.

FCD-led increases in irrigation expansion would be modest. Ground water irrigated area would increase by 3,300 ha, 1.5% of the current area of 223,000 ha, and usage by 43 Mm3. Minor surface water irrigated area would increase by 900 ha, 0.2% of the current area of 351,000 ha, and usage by 11 Mm3. The area irrigated by mechanized means would increase by 2,700 ha, 0.7% of the current area of 383,000 ha. These impacts are composed of substantial decreases in irrigation (all types) in the Baulai River Improvement Project and the Kalni-Kushiyara River Improvement Projects, reflecting a net shift from winter to summer crops, balanced by modest increases in irrigation in most of the other projects (Figure 13).(4)

Annual diesel fuel consumption for irrigation would increase accordingly by 0.5 million litres, 0.7% of current requirements of 76 million litres.

Annual agrochemical use -- of interest for reasons of ecologic/water quality, human health, economic, etc. -- would increase. Annual pesticide use would increase by 47 tonnes, or 9% of current usage of 530 tonnes. Annual fertilizer use would increase by 46,000 tonnes, 20% of current usage of 226,000 tonnes.

Soil quality would need to be managed more carefully in areas provided with full flood control/controlled flooding facilities, and in areas converted to HYVs.

Fodder supplies would shift, with some increasing and others decreasing. There would be increases in biomass byproducts (straw, husks, and so on) proportionate to increases in primary agricultural production described previously. Also, provision for fodder as a second or third, additional, crop on 26,000 ha has been included in Baulai River Improvement Project and Kalni-Kushiyara River Improvement Project. Winter grazing area (defined as F0, F1, and F2 winter fallow plus perennially fallow highlands) would decrease by 54,000 ha or 7.0% of the current area of 779,000 ha.

Homestead agricultural (spices, fruit trees, vegetables, livestock, etc.) production would increase on 6,700 ha or 10% of current regional homestead area of 65,000 ha, due to new and raised homesteads from spoil (700 ha), reduced flood damage on flood-protected homesteads (6,400 ha), minus homestead area taken for project works (400 ha).

Other projects.  Agriculture would benefit from several projects (see box). The projects Applied Research for Improved Farming Systems, Fisheries Biological Management, FEAVDEP and NEMREP each imply diversification of land use away from field crops, in particular rice cultivation, to uses such as agroforestry, and swamp forest reed land, and flood plain grassland for fish habitat, village erosion protection, and production of biomass products (fuel, building materials, fodder, green manure, and so on). The areas under these non-agricultural usages would expand into areas now occupied in part by agriculture, in particular (mainly highly flood-damage prone) rice cultivation. Impacts as a percentage of regional rice cropped area and rice production would be small. The impact on agriculture is therefore negative, but the overall biophysical and socioeconomic impact is positive.

Water quality impacts
FCD projects.  Water quality (as experienced by domestic consumers, fisheries, and wetlands) changes cannot be quantified, but would be affected in a number of ways. Drainage improvement would tend to improve water quality, by increasing flushing and flushed volume and duration, and decreasing stagnant water volume and duration. Flood control would improve water quality at some times and places, by eliminating flooding of domestic-supply tube wells and pit latrines for example, and worsen it at others, by decreasing flushing and increasing stagnant water volume and duration. The FCD-led increases in pesticide use (see above) would contribute to water contamination, especially in low pockets surrounded by HYV cultivation. The FCD-led increases in fertilizer use would increase nutrients available to the openwater fishery, but could also aggravate eutrophication problems.

Other projects. Water quality would be improved by a number of projects (see box).As has been mentioned, the Urban Potable Water Project would increase urban domestic waste water volume. There would be no negative impacts on water quality from any other non-FCD projects.

Openwater fisheries impacts
FCD projects. Open water fisheries habitat and production would be altered:
  • Floodplain (defined as F1, F2, F3, and F4 areas, based on monsoon flooding) would decrease by 49,000 ha, or 2.3% of the total current regional floodplain area of 1.2 million ha.
  • Beel area would increase by 70 ha, or 0.1% of the total current regional beel area of 60,000 ha, reflecting the impacts of beel bunding and water retention behind regulators, less beel area lost to other land uses.
  • River and channel area will increase by 1,400 ha, or 4.0% of the current regional area of 35,000 ha, reflecting excavation of 74 million cubic meters of channel sediment.
  • The number of river duars will increase by 42 or 14% of the FWO total of 310, reflecting mitigation of duars that would be lost in the FWO scenario due to siltation in the Baulai and Kushiyara Rivers. Impacts on production would be positive, but have not been quantified.
  • Major and minor channels will be closed permanently at 48 locations, eliminating fish migration along these routes.
  • The Surma-Kushiyara-Baulai Project has the greatest quantifiable negative impact on fish production (-3,900 tonnes annually). This is due to the project's large size (320,000 ha gross area), and the pessimistic assumption that the overall migration impact will be -20% (M = 0.8). The project includes dredging for habitat rehabilitation in the Kaliajuri mother fishery and key wetland site, and flood control works designed to preserve the ecological character of the fishery by leaving the lowest and most important migration routes open.
  • The Manu River Improvement Project has the next greatest negative impact on fish production (-2,900 tonnes annually). Assumed impacts on Hakaluki Haor, a key wetland and mother fisheries site, account for most of this: it has been assumed pessimistically that Hakaluki Haor would be completely destroyed as a mother fisheries site by sediment deposited there during diversion events. Some mitigation appears to be possible, in the form of structural confinement of sediment deposition to selected areas.
Dredging implementation-phase impacts on fish populations are not known and need to be investigated during feasibility studies. Dredging would be performed in the dry season (wet season velocities are too high) when turbidity under normal conditions is low and stresses on fish populations are already at their highest. A key issue will be possible disruption, particularly of benthic biological communities, due to sedimentation and high-velocity turbid plume flows; and the spatial and temporal scale of the fisheries impact. Some methods are in use to mitigate aquatic impacts of dredging, for example, use of booms and curtains to protect valued areas.

For manual excavation, fisheries impacts occur during the site preparation phase when channels are drained out usually resulting in total catch of fish populations in the affected reach. The regional biophysical and economic impacts of this activity are not readily distinguishable from normal fishing activities, however.

The overall quantified impact on openwater fisheries annual production would be a decrease of 10,600 tonnes or 11.0% of current regional annual production of 96,000 tonnes, with over half due to losses due to flood protection measures included in the Surma-Kushiyara-Baulai Project and the assumed destruction of Hakaluki Haor by the Manu Diversion Project. The overall quantified impact includes FCD-induced changes in migration access and water quality for most of the projects.

No impact on the three fish species thought to be threatened is anticipated, but further study of these species would be needed to confirm this.

Other projects.  Openwater fisheries would benefit from a number of projects (see box). Benefits from these projects would help to mitigate the adverse fisheries impacts of the FCD projects; in terms of overall openwater fish production, the net impact (FCD+other) would be significantly positive. The same concerns that were mentioned above with respect to FCD dredging would apply to Dredging for Navigation. There would be no negative impacts on openwater fisheries from any other non-FCD projects.

Aquaculture impacts
FCD projects.  Flood-free pond area would increase by 1,600 ha or 8.3% of the regional total of 18,700 ha. The potential increment in annual aquaculture production would be 1,600 tonnes, 8.8% of the current regional production of 18,000 tonnes.
 

Other projects. Aquaculture would benefit from several projects (see box). There would be no negative impacts on aquaculture from non-FCD projects.

Navigation impacts
FCD projects.  Navigation would be benefitted by river and channel excavation, and disbenefitted by the 48 closures of major and minor channels at embankments and across spill channels.

Other projects.  Navigation would benefit from several projects (see box).  There would be no negative impacts on navigation from non-FCD projects.

Biodiversity impacts
FCD projects.  The impact on biodiversity would be mainly adverse:
  • Winter wetland area (defined as F3 land lying fallow in winter, plus perennially fallow lowlands, plus beels and channels) would decrease by 7,000 ha or 5.7% of the regional total of 124,000 ha.
  • Summer wetland area (defined as F1, F2, and F3 land lying fallow in summer, plus perennially fallow lowlands, plus beels and channels) would decrease in area by 50,000 ha or 11% of the regional total of 440,000 ha.
  • Key wetland sites: Manu River Improvement Project would adversely affect Hakaluki Haor. Jadukata-Rakti Project and Sarigoyain-Piyain Project could benefit the key wetland sites and mother fisheries at Tangua Haor and Companyganj by reducing sediment infilling.
Swamp forest and reed swamp would not be affected. About half (250 ha) of the region's remaining floodplain grassland (550 ha) could be adversely affected by Surma Right Bank Project.

No threats to particular threatened and commercially threatened plant and animal species are apparent with the information currently available, except for the obvious threat to floodplain grassland-dependent species. Further study would be required to understand species impacts of the elimination of one of the two remaining areas of this community. Further study of the other threatened and commercially threatened species would be needed to confirm lack of impact.

Openwater fishery biodiversity impacts were discussed above.

Other projects.  Biodiversity would benefit from a number of projects (see box). Benefits from these projects would help to mitigate adverse impacts of the FCD projects on biodiversity, including migratory waterfowl populations (see below). There would be no negative impacts on biodiversity from non-FCD projects.

Impacts on areas outside flood protection within the region; areas outside the region; and migratory populations
FCD projects.  Three areas in the region -- the Mogra basin, Hakaluki Haor, and the lower Sarigoyain River basin -- will remain both outside of flood control embankments and may be vulnerable to displaced flooding from Plan FCD projects, which could cause increased flood damage to crops, homesteads, and roads in these unprotected areas.

There would be no hydrologic or sediment impact on areas downstream of the region, given conditions at the region's outfall. A possible exception could be transient effects due to turbidity from dredging.

Migrating waterfowl populations will be adversely affected by the overall reduction of winter wetland areas and the adverse impacts on Hakaluki Haor. This could be somewhat compensated by positive impacts on Tangua Haor and Companyganj area.

Pesticide pollution of regional surface water outflows would increase slightly.

Other projects.  Areas outside the Northeast Region would benefit from improved water quality of regional surface water outflows due to a number of projects (see water quality box). Migratory fish populations would be benefitted by a number of projects (see openwater fish box).

Other biophysical impacts
Dredging could have other adverse impacts, in addition to the fisheries impacts mentioned above. It involves movement of vast quantities of spoil, initially in the form of a water/sediment slurry, which must be properly managed (proper settling basins, deposition in acceptable locations, and so on), or negative impacts can be considerable: spoil deposited in areas where it is not wanted or destructive, turbid flows into the original dredged or other water body with unwanted effects, and so on. Another concern may be a need to check sediments for toxic chemicals, in channels downstream of industrial facilities. Proper environmental management will be key. Incentive to handle slurry/spoil properly should be built into contracts (pay per volume moved will be an invitation to carelessness).
9.6.2 Socioeconomic Impacts
Displacement impacts
Some rural residents will be very directly impacted through impacts on homestead lands. FCD works will displace 107,000 people from rural homesteads; the Kalni-Kushiyara River Improvement Project accounts for almost half of this. In this and other projects, compensation of the impact on the regional stock of homestead land would be achieved by constructing new homestead areas from excavation spoil.
Homestead flood protection
The 6,400 ha of homestead which would be protected from flooding are occupied by 1.4 million residents, who would experience less flood damage to possessions, including the homestead plot itself and to homestead agricultural production.
Urbanization and migration impacts
Strategy implementation would tend to accelerate urbanization, some of which would occur as rural areas shift over to urban economic activities, and some as rural-to-urban migration. Both urban and rural economic and environmental conditions would improve over the FWO forecast, but improvement in urban conditions would proceed more rapidly. One result would be that per-household rural income would improve, with incremental rural gains being shared among a smaller number of people. In particular, it is expected that the Narsingdi-Narayanganj Project and the Narsingdi District Project would boost urban population in this area by 1 million. Some of this represents more rapid urbanisation of rural landless people already within the area (especially as villages along the Dhaka-Sylhet and Dhaka-Chittagong corridors urbanise), and the rest represents in-migration from other areas. Integration of this area with the Dhaka mega-urban field will be accelerated as well.
Socioeconomic equity and impacts on landless people
The strategy will reduce the total number of rural landless people in the region compared to the FWO situation, mainly by boosting the urban population of the Narsingdi-Narayanganj area through faster urbanisation of local landless people and increased in-migration to urban areas of rural landless people from other areas.

The benefits of strategy implementation will accrue to different sections of the society in varying proportions. FCD initiatives will mainly benefit landowners, which should slow down the overall rate at which small farmers become marginalized and eventually landless. The strategic thrusts for improved urban environment and improved liveability of rural settlements will benefit all strata of the population with optimum equity.

In FCD projects, the net incremental increase in employment in project agriculture less employment lost in fisheries, is composed of 66,000 jobs which would accrue to landowners and 16,000 jobs which would accrue to hired labourers (that is, landless people). Additional jobs in downstream post-harvest activities would also be created.

The overall figure for hired labourers masks the fact that as many as 41,000 jobs in the openwater fishery (about 12% of jobs in the sector) could be lost. Additional downstream jobs in post-catch processing would also be lost. This represents a significant negative impact on fishing families, particularly poorer families dependent upon subsistence fishing, as a group.

Gender equity
The strategic thrust to improve liveability of rural settlements would improve the conditions in which most women spend most of their lives and perform most of their work. This would also support expansion of household-based employment. The initiatives on potable water, both rural and urban, will benefit women, who collect and use most domestic water, more than proportionately.

Several of the strategic thrusts would support crop diversification, which could be positive for women, in the sense that adoption of non-traditional crops might provide an opportunity for eased cultural constraints on women's involvement in field activities in agriculture.

Otherwise, the other strategic thrusts benefit women mainly as members of households; to the extent that women share in the total work, income, assets, and so on of their households, to that extent they will benefit from the strategy. The other strategic thrusts neither fortify nor transform the social construction of gender roles as these would exist in urban and rural settings.

Literacy
The strategy will not impact literacy directly, but the improvement in general economic conditions and better living conditions in rural and urban areas will have positive impact on the people's attitudes towards and ability to afford education for their children. The elasticity of income for education is believed to be greater than one at the above-subsistence level: once basic food requirements are met, people spend more on education.

Well-protected settlement areas will prevent disruption of education from flooding of school buildings and roads.

As higher education facilities are concentrated in urban areas, improved protection of the roads and water links between the villages and urban centres would have some impact on higher enrolment in secondary and college level education. This is particularly true for Sylhet Region which has few colleges compared to other areas; these are mostly concentrated in urban centres where female enrolment is low.

While improved access will help to increase gross enrolment rate, increased household income is expected to reduce the dropout rate significantly.

Water and sanitation
The implementation of the proposed strategies on improved urban environment and improved liveability of rural settlements will contribute to achieve the national goal for universal coverage of potable water for drinking. With improved accessibility and motivation, the use of tube well water for all purposes can be expanded. This will help to reduce the incidence of water-borne diseases and will have positive impact on health and personal hygiene.

Tube well maintenance by women will enhance their role and status in the community. In addition, increased accessibility will reduce the labour in drawing and managing domestic water supplies, traditionally women's work.

Proposed initiatives (Urban Sanitation, Rural Water and Sanitation), will also contribute to improved sanitation through proper disposal of human waste and waste treatment.

Nutritional status
Enhanced production systems including pond aquaculture in seasonally flooded areas and integrated development of the deeply flooded areas will contribute to increased production of high value nutritious crops, fish, and livestock and will increase their availability in the market.

The FCD projects alone would result, relative to FWO conditions, in food availability per person increasing by 10% for rice, by 12% for other crops, and decreasing by 11% for fish. The impacts of the total strategy would be significantly more favourable than this. Increased aquaculture fish production (increase of 11% with fewer ponds at risk of regular flooding) would partly offset decreasing openwater fish production, but will provide little consumption benefit to poorer groups.

Income is directly correlated with nutritional status. With increased per capita income, the extent of child malnutrition (stunting, wasting, underweight) would decline. The impact on nutritional status will be less in rural than urban areas due to the lower impact of strategy implementation on rural incomes.

Increased household income would be accompanied by increased expenditure for food. This will contribute to ensure minimum caloric intake for the vulnerable population. The average incremental income would be sufficient to overcome absolute poverty (defined as Tk 4,800 per person per year), but many poorer households' income would remain below this level.

Life expectancy
The increase in aggregate household income expected as a result of strategy implementation would directly contribute to overall improvement in living conditions, particularly through improvement in health and nutritional status. It is likely that with increased household income, per capita expenditure on nutritious food, sanitation and health care will increase. All these together will have positive impact on life expectancy, particularly on the reduction of infant and child mortality.
Socioeconomic impacts of biodiversity and wetland changes
People dependent on floodplain grassland and on wetlands will be adversely affected, in proportion to the impacted areas noted above. This impact will be localized and will mainly affect poorer people who are most dependent on these types of resources.

9.7  MODIFICATION OF EXPECTED IMPACTS BY PARTIAL AND/OR DIFFERENTLY PHASED IMPLEMENTATION

9.7.1 Projects Affected by Tipaimukh Dam
Four projects (Upper Surma-Kushiyara River Project, Surma Right Bank Project, Surma-Kushiyara-Baulai Basin Project and Kushiyara-Bijna Interbasin Project) would be affected by Tipaimukh Dam. For phasing purposes, these projects are grouped together (Regional Plan Section 9.3, Group SED) for implementation commencing in Year Four, to allow additional time for resolution of the Tipaimukh Dam issue.

If the Tipaimukh Dam/Cachar Plain Project is delayed beyond this point (i.e. is neither implemented nor definitely dropped), then implementation of the Group SED projects would be delayed further. This would significantly alter the nature of the impacts produced by several other initiatives. For example, if the Upper Surma-Kushiyara Project and Surma-Kushiyara-Baulai Basin Project were not implemented:

The Kalni-Kushiyara River would likely experience a continuation of trends of increasing flood levels and sedimentation rates. Much greater maintenance dredging effort would be required to reverse these trends than is presently envisaged in the Kalni-Kushiyara River Improvement Project.

Large magnitude spills (possibly increasing over time due to channel changes) would continue to occur into the Central Basin from both the Surma River and Kushiyara River. This would significantly reduce the effectiveness of initiatives such as the Baulai River Improvement Project and Kushiyara-Bijna Interbasin Project.

In the case of extended delay in resolution of the Tipaimukh Dam issue, one approach would be to proceed with key components of the Upper Surma-Kushiyara Project and Surma-Kushiyara-Baulai Basin Project which would be feasible to construct during the extended interim period. Such components of the Upper Surma-Kushiyara Project involve regulation of spill channels and khals that divert water from the Surma River into the Kushiyara River system. Key components of the Surma-Kushiyara-Baulai Basin Project involve regulation of spill channels from the Surma River into the deeply flooded Central Basin, and re-excavation of important distributary channels which drain the inter-basin and discharge into the Baulai River. Components that might be postponed until after a final decision on the dam is reached includes raising and upgrading full flood control embankments on the Upper Surma-Kushiyara Rivers and upgrading and construction of new submersible embankments on the lower Surma-Baulai River and Kushiyara-Kalni River.

9.7.2 Projects Affected by Alluvial Fan Instability
The Piyain Improvement Project, Jadukata-Rakti Improvement Project, and Upper Someswari River Basin Project all contain measures for improving the stability of land affected by alluvial fans. However, at present, the channels on these fans are all poised to develop avulsions which could substantially alter the downstream hydrological regime and drainage patterns in the project area. The effectiveness of the proposed measures and the nature of the impacts from these projects will be strongly dependant on the timing for their implementation. This is because the tendency for channel changes will not remain constant over time but is generally progressive. For example, an avulsion path may originate as a small khal or spill channel and then enlarge during successive floods by bank erosion as flow is captured from the old channel. If the avulsion path is closed early on, before it develops into a major channel, relatively minor measures may be required. If the works are delayed until most of the flow is carried by the new avulsion channel, it may be no longer feasible to close it. Furthermore, even if a closure can be made, the scale of the impacts from this work may be substantial, both on the newly formed channel and the old channel. Therefore, the control measures described in these projects implicitly assume immediate implementation. If the work was not implemented immediately, the overall concept for stabilizing the fan would have to be re-assessed. In this case, a decision to delay the work is equivalent to assuming it will not be implemented at all.

9.8 IMPACTS BY SUBREGION

9.8.1 Introduction
This section describes the main physical impacts from Regional Plan initiatives in various geographical sub-regions. The object of the discussion is to illustrate the spatial distribution of impacts of the Plan in the region. Several different classification schemes can be used to delineate sub-regions, such as physiography, land-use, or depth of flooding. For the purposes of this discussion, the region has been divided (primarily on the basis of physiography), into six main sub-regions:
  • Eastern seasonally flooded floodplain land
  • Northern alluvial fans
  • Central Basin
  • Western seasonally flooded floodplain land
  • Southern piedmont floodplains
  • Peri-urban areas
The general extent of these sub-regions is can be seen in Regional Plan Figures 2, 4, and 14 (Peri-Urban Area).
9.8.2 Eastern Seasonally Flooded Floodplain
The eastern seasonally flooded areas include the floodplain of the Surma-Kushiyara Rivers and the inter-basin lands adjacent to the main rivers. The sub-region extends from Amalshid on the east where the Barak River bifurcates at the Indian Border, to near Chhatak on the Surma River and near Sherpur on the Kushiyara River. Projects in this sub-region include:
  • Upper Surma-Kushiyara River Project
  • Surma Right Bank Project
  • Sarigoyain-Piyain Project
These projects will eliminate spills from the main rivers during both the pre-monsoon and monsoon season so that during the flood season, runoff in the low-lying inter-basins will be derived only from internal rainfall. The closure of major spill channels will increase the relative distribution of flows carried by the Surma River. However, flow regulation from Tipaimukh Dam will reduce the flood inflows, so that the flood magnitudes will be reduced on both the Surma and Kushiyara Rivers. Consequently, the inter-basin lands will be more isolated from the main rivers since banks will not be overtopped, and inflows of water and sediment from spills will be eliminated. The main rivers will adjust to the reduced flood magnitudes, lower sediment inflows and increased lateral confinement. It is expected that some reaches (particularly the Kushiyara River) will transform into smaller, more stable channels with fewer deep scour holes and larger, more prominent sand bars.
9.8.3 Northern Alluvial Fans
The alluvial fans bordering the Meghalaya Hills extend from the Dhalaiganj River near Companyganj in the east to the Someswari River in the west. Projects that fall in this sub-region include:
  • Sarigoyain-Piyain Project, Dhalaiganj improvement component
  • Jadukata-Rakti River Improvement Project
  • Upper Kangsha River Basin Project, Someswari River component
The Plan recognizes the inherent instability and high risks that are associated with developments on fans. Therefore, the Plan has avoided initiatives that would attempt to confine the fan channels by narrow embankments. Instead, it is recommended that the fans be allowed to occupy a wide active floodway, which will be used for storing sediment and conveying flood flows. Initiatives have been restricted to (1) stabilizing inactive or less active portions of the fan so they will be safe from future avulsion hazards, or (2) preventing new avulsions from developing by closing spill channels that threaten to capture the main river flows. Therefore, the negative impacts of projects in the fans should be small. However, this also implies that damages from flooding, erosion and sedimentation will continue to occur to existing developments within the active floodway of the fans.
9.8.4 Central Basin
The projects in the Central Basin include:
  • Surma-Kushiyara-Baulai Basin Project
  • Baulai River Improvement Project
  • Kalni-Kushiyara River Improvement Project
  • Kushiyara-Bijna Inter-Basin Project
  • Jadukata-Rakti River Improvement Project
  • Updakhali Project
  • Dharmapasha-Rui Beel Project
Impacts from these developments will be primarily felt during the pre-monsoon and post-monsoon season. Project impacts are expected to be minor during the monsoon season when the sub-region, and the initiatives will be inundated.

The main project impacts in this sub-region derive from three factors:

Spills of pre-monsoon floods from main river courses into the low-lying haor basins will be reduced due to regulation of spill channels and completion of new submersible embankments along the major rivers. Consequently, during the pre-monsoon season, drainage requirements will be primarily determined from local runoff rather than from externally generated flood inflows. The key project that accomplishes this regulation of spills into the Central Basin is the Surma-Kushiyara-Baulai Basin Project. In addition, the Upper Surma-Kushiyara River Project, although located outside the sub-region, also is critical to reducing inflows along the Kushiyara River.

Runoff in the Central Basin will be organized and conveyed into several major drainage channels that will discharge into the main rivers. At present, much of the existing drainage system has been obstructed by past channel closures, channel changes due to morphologic processes or local siltation. The initiatives includes a major program to restore the drainage capacity of the basin lands through a program of channel re-excavation and re-alignment.

Shoals and obstructions on the main river channels will be excavated to lower pre-monsoon water levels (to reduce spills into the Basin) and post-monsoon water levels (to hasten post-monsoon drainage).

Consequently, it is expected that the Central Basin will become a more stable, low energy environment, since the magnitude of the driving forces (the water and sediment inflows) will be reduced considerably.

9.8.5 Western Seasonally Flooded Floodplain
This sub-unit includes the floodplain of the Old Brahmaputra River as well as Piedmont floodplains draining the Susang Hills. The projects in this sub-unit include:
  • Upper Kangsha Project
  • Mrigi River Drainage Improvement Project
The proposed works on the Mrigi River involve channel re-excavation and drainage improvements while the works in the Upper Kangsha River Project involve construction of full flood control embankments, a flow diversion to Mogra River and a major program of channel straightening and loop cutting. Impacts from the Mrigi project will be minor, while major impacts are expected to occur from the Upper Kangsha River Project, both in the direct project area and further downstream outside the project area.
9.8.6 Southern Piedmont Floodplain
This sub-unit includes all of the piedmont streams draining the Tripura Hills in India. Projects in this sub-unit include:
  • Manu River Improvement Project (Manu River and Dhalai River)
  • Habiganj-Khowai Improvement Project (Khowai River, Karangi River and Sutang River)
The primary effect of these projects will be to reduce monsoon season flooding by either confining main channel flows and preventing spills (Habiganj-Khowai Project) or by reducing flood magnitudes by diverting flows into an adjacent basin (Manu River Improvement Project).

The magnitude of the impacts from both projects is expected to be large. However, the nature of the impacts will be very different. For example, spills from the Khowai River into adjacent Karangi River will be greatly reduced by extending the Khowai embankments upstream. Therefore, impacts will be associated with reduced flooding on the Karangi River and increased flood flows on the lower Khowai River. The main impacts on the Manu River Project will be associated with the reduced flood discharges below the diversion along the Manu and the impact of the diversion of water and sediment into Hakaluki Haor.

9.8.7 Peri-Urban Area
This sub-unit includes the districts of Narayanganj and Narsingdi, which are expected to take on the role of market gardens for the Dhaka urban and peri-urban population, as urban development spreads to the northeast and displaces market gardening from current closer-in areas. Projects in this sub-unit are:
  • Narsingdi-Narayanganj Project
  • Narsingdi District Project
These projects are intended to protect these peri-urban areas for flooding, to facilitate high-value agriculture and reduce flood damage to homes and businesses. They are not expected to affect hydrologic or morphologic conditions outside the project areas.

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