Technical Assistance Consultant’s Report
Project Number: 44167-012 December 2013
Bangladesh: Main River Flood and Bank Erosion Risk Management Program (Financed by the Japan Fund for Poverty Reduction)
Prepared by Northwest Hydraulic Consultants, Canada
In association with Resource Planning and Management Consultants Ltd., Bangladesh
For Bangladesh Water Development Board
This consultant’s report does not necessarily reflect the views of ADB or the Government concerned, and ADB and the Government cannot be held liable for its contents. (For project preparatory technical assistance: All the views expressed herein may not be incorporated into the proposed project’s design.
Government of the People's Republic of Bangladesh
Bangladesh Water Development Board
Project Preparatory Technical Assistance 8054 BAN Main River Flood and Bank Erosion
Risk Management Program
Final Report, Annex A Priority Sub-Reach Selection & Sub-reach Descriptions
September 2013
In association with
Resource Planning & Management Consultants Ltd.
Asian Development Bank
Funded by the Japan Fund for Poverty Reduction
Government of the People’s Republic of Bangladesh Bangladesh Water Development Board
Project Preparatory Technical Assistance 8054 BAN Main River Flood and Bank Erosion
Risk Management Program
Final Report, Annex A Priority Sub-reach Selection and Sub-reach Descriptions
September 2013
PPTA 8054: BAN- Main River Flood and Bank Erosion Risk Management Program
Document Background
Title: Priority Site Selection and Sub-reach Descriptions Annex A Principal Author: Knut Oberhagemann, Northwest Hydraulic Consultants Contributions: Team; Background data largely from the National Water Resources Database provided by CEGIS under different subcontracts; Some figures and graphs from CEGIS under different subcontracts; GIS presentations by consulting team, Inundation information from flood modelling, Annex D Early version: Annex A of Interim Report and draft Final Report Final version: September 2013, Re-printed 28 February 2014
Document Development
Draft Final 15 June 2013 Revision R1, 17 July 2013 Formatting, spell check, font change, justification R2, 27 July 2013 Formatting, spell check, font change, justification R3, 28 July 2013 Page setup and print R4, 2 Aug 2013 Inclusion of the MCA for priority site selection R5, 21 Aug 2013 Inclusion of parameters for economic feasibility R6, 31 Aug 2013 Formatting and page setup R7 21 Sep 2013 Setup cover page, change month name on header- footer and correction in river areas %. R8, 30 Sep 2013 Final check R9, 30 Sep 2013 Formatting for final print R10, 28 Feb 2014 Reprinted R9 Review Knut Oberhagemann, 1 August, 2013 Knut Oberhagemann, 30 August, 2013 Knut Oberhagemann, 30 September 2013
Cover page: Erosion upstream of Enayetpur Spur, December 2012 (Photo: Knut Oberhagemann)
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MAIN REPORT
ANNEXES
Annex A Priority Sub-reach Selection & Sub-reach Descriptions Annex A1 Priority Sub-reach Selection Annex A2 Sub-reach Description Annex B Background Data Annex B1 National Water Resources Database Annex B2 Socio-economic Data Annex B3 Surveys and Field Visits Annex C Institutional and Financial Assessment Annex D Hydrology and Flood Modelling Annex E River and Charland Morphology and River Engineering Annex F Design Issues Annex F1 Geotechnical Investigations Annex F2 Technical Designs Annex G Economic Feasibility Annex G1 Project Cost Annex G2 Economic Assessment Annex H Implementation and Procurement Planning Annex I Social Gender Equity Strategy & Action Plan Annex J Environmental Impact Assessment Annex K Involuntary Resettlement Annex K1 Resettlement Framework Annex K2 Resettlement Plan
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Table of Content
ANNEX A1 : PRIORITY SITE SELECTION ...... 1 1 Multi-Criteria Assessment (MCA) of Tranche 1 Interventions ...... 3 1.1 Approach and Key Criteria ...... 3 1.2 Criteria ...... 4 1.2.1 River bank erosion ...... 4 1.2.2 Flooding...... 4 1.2.3 Social Fabric ...... 5 1.2.4 Ease of engineering ...... 6 1.2.5 Complements existing work ...... 7 1.2.6 “No regret” ...... 8 1.2.7 Safeguards ...... 9 1.2.8 Cost ...... 10 1.2.9 Benefits ...... 11 1.3 MCA Weighting and Scoreboard ...... 12 1.4 Final Selection ...... 13 ANNEX A2 : SUB-REACH DESCRIPTIONS ...... 15 1 Jamuna Right Bank 1 –Jamuna Bridge – Shahjadpur Priority ...... 17 2 Jamuna Right Bank 2 –Pabna ...... 29 3 Jamuna Left Bank 1 – Tangail ...... 33 4 Jamuna Left Bank 2 – Aricha Priority ...... 37 5 Padma Left Bank 1 – Paturia – Harirampur Priority...... 48 6 Padma Left Bank 2 – Harirampur - Mawa ...... 58 7 Padma Left Bank 3 – Mawa-Padma Outfall ...... 62 8 Padma Right Bank 1 – Ganges Barrage-Goalando ...... 66 9 Padma Right Bank 2 – Faridpur to Arial Khan ...... 67 10 Padma Right Bank 3 – Arial Khan to Sariatpur ...... 69 11 Meghna Right Bank 1 – Bhedarganj ...... 71 12 Meghna Left Bank 1 – MDIP ...... 73 13 Meghna Left Bank 2 – Matlab to Chandpur ...... 75
Note: the Tranche-2 and Tranche-3 work is subject to further verification during the preceding tranches.
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ANNEX A1 : PRIORITY SUB-REACH SELECTION
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1 Multi-Criteria Assessment (MCA) of Tranche 1 Interventions
1.1 Approach and Key Criteria MCA is an appropriate approach when comparing quantitative and qualitative data that are otherwise incomparable. This is especially true for prefeasibility level assessment, when not all data are quantified or quantifiable.
In this PPTA, an MCA is used to select the sub-reaches to be brought forward for feasibility assessment and potential inclusion in Tranche 1. The MCA is the first step to identify three suitable sub-reaches, to which, in a second step, a simplified economic feasibility analysis will be applied for confirmation of their suitability. The purpose is to arrive at two or three sub-reaches to be covered by Tranche 1 subprojects.
We have identified issues and criteria in two categories, means-ends and impacts (Table 1-1). Issues in the means-ends group are vulnerability and planning-engineering aspects, and relate to the identification of priority sites suitable for MRP interventions. Issues in the impact group are safeguards and cost-benefit, and relate to acceptability of the potential impacts of the interventions. Criteria were then identified for each issue, nine criteria in total, each of which can have up to three sub-criteria. In addition, we assess if the identified priority interventions conflict with other planned major interventions. An example would be the Padma Bridge construction, which impacts on two sub-reaches directly and has the potential to affect four sub-reaches downstream.
Each of the following subsections systematically describes each criterion. In order to be transparent, we follow the same structure throughout. Starting with a short justification of the criterion we provide details about how we classify the criterion and how we arrived at the values used for the classification. The latter is important as we are using primary, qualitative data, and quantitative data, based on a more general assessment of an overall situation. Finally, we conclude with detailed tables explaining each sub-criterion. When there are measured data, this contains ranking and definition of limits, while for qualtitative assessment detailed descriptions of the considerations leading to the ranking are provided for each sub-reach.
Table 1-1: Grouping of criteria Broad Category Main Issues Criterion Means and ends Vulnerability Riverbank erosion Flooding Social fabric Planning and engineering Ease of engineering interventions Complements existing work/schemes Is consistent with predicted/expected future planform (“no regret”) Impacts Safeguards Social and environmental Cost and benefits Cost deviation from average low-cost work Expected benefits for different sectors
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1.2 Criteria 1.2.1 River bank erosion JUSTIFICATION: Riverbank erosion along the main rivers has resulted in substantial land losses in Bangladesh and impacts on the development of the floodplains bordering the main rivers.
DETAILS FOR EACH SUB-CRITERION: Historic Riverbank Erosion This sub-criterion is based on primary data. Riverbank erosion is expressed as erosion per km of bankline. It is the result of the total loss of land in one sub-reach divided by the length of riverbank in this sub-reach. The reference lines are the 1973 and the 2010 bankline.
Recent Riverbank Erosion This sub-criterion follows the same process as for historic riverbank erosion, only for the period 2007 to 2012.
Future Riverbank Erosion This sub-criterion cannot be based on primary data. Given the uncertainties the most likely scenario for the future around 10 - 15 years has been developed. The timeframe of 10 – 15 years is relevant as the PPTA prepares an MFF with around 10 years implementation period. Consequently, future developments are highly relevant for any interventions that target the reduction of river instability and maximization of reclamation of land lost during the erosion process of the last 30 years. The criteria selected were expected substantial erosion, coded “1”, no substantial erosion or accretion, coded “0”, and likely accretion, coded “-1”.
DETAILED TABLES:
CATEGORY SUB-CATEGORY Unit JRB1 JRB2 JLB1 JLB2 PLB1 PLB2 PLB3 PRB1 PRB2 PRB3 MRB1 MLB1 MLB2 Area sq km 580.4 914.6 787.5 1,211.8 681.7 789.5 440.9 876.3 1,055.2 801.4 435.1 277.5 440.5 floodplain ha 44,416.0 72,178.0 71,812.0 82,520.0 52,491.0 69,239.0 29,738.0 74,638.0 75,454.0 55,890.0 33,099.0 20,026.0 27,981.0 bank length km 36.7 66.0 21.2 56.3 24.8 30.4 47.6 55.4 50.3 46.5 34.1 21.4 24.4 erosion total (1973-2010) ha 5,561.4 2,053.5 5,224.2 14,579.7 8,312.9 2,048.0 6,042.9 7,673.6 9,125.9 8,356.6 6,313.4 2,022.0 1,096.1 recent (2007-2012) ha 478.7 427.4 125.3 694.4 70.8 182.2 390.2 1,027.2 597.2 857.5 875.1 115.6 256.2
ABSOLUTE FIGURES CATEGORY SUB-CATEGORY Unit JRB1 JRB2 JLB1 JLB2 PLB1 PLB2 PLB3 PRB1 PRB2 PRB3 MRB1 MLB1 MLB2 erosion total (1973-2010) km/km 1.52 0.31 2.46 2.59 3.35 0.67 1.27 1.39 1.81 1.80 1.85 0.94 0.45 recent (2007-2012) km/km 0.13 0.06 0.06 0.12 0.03 0.06 0.08 0.19 0.12 0.18 0.26 0.05 0.11 future (2012-2020) + / - 0 0 1 1 1 -1 1 1 1 1 1 0 0
RANK erosion total (1973-2010) 7 13 3 2 1 11 9 8 5 6 4 10 12 recent (2007-2012) 4 9 11 5 13 10 8 2 6 3 1 12 7 future (2012-2020) 9 9 1 1 1 13 1 1 1 1 1 9 9
1.2.2 Flooding JUSTIFICATION: Flooding is a major development impediment as it causes sporadic, unpredictable but substantial damages affecting the life on the floodplains in multiple negative ways.
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DETAILS FOR EACH SUB-CRITERION: Average Flood This sub-criterion is based on primary data. The analysis of Radarsat flood season images allows the determination of areas in each sub-reach flooded during a flood with a 2-year return period, or an average flood. As such this sub-criterion reflects on the amount of land potentially taken from agriculture during normal flood years.
Mean Flood Same as before this criterion is based on primary data, however for a higher return period. The range chosen lies between return periods of 5 to 15 years. This represents roughly the boundary between good flood and bad flood and could be considered to be the amount of flooded land that is accepted as an off-set of the beneficial fertilization of fields.
High Flood Following along the same lines, as the other two sub-criteria, this flood represents areas flooded during some of the highest floods observed in Bangladesh during the recent past, namely 1998, 2004, and 2007. These were damaging floods and flooding to this extent is unwelcome.
DETAILED TABLES:
CATEGORY SUB-CATEGORY Unit JRB1 JRB2 JLB1 JLB2 PLB1 PLB2 PLB3 PRB1 PRB2 PRB3 MRB1 MLB1 MLB2 Area sq km 580.39 914.56 787.5 1211.82 681.68 789.46 440.87 876.27 1055.15 801.43 435.14 277.53 440.48 floodplain ha 44,416 72,178 71,812 82,520 52,491 69,239 29,738 74,638 75,454 55,890 33,099 20,026 27,981 Total Area without River ha 44,417 72,179 71,813 82,561 52,492 69,242 29,740 74,640 75,456 55,891 33,100 20,026 27,983 Flooded Area 1998 ha 31,946 33,138 45,807 60,399 32,617 42,054 8,860 25,829 38,738 31,054 21,683 7,396 6,522 approximate return period year 20 40 20 40 40 40 40 40 40 40 40 40 40 1998 % 72% 46% 64% 73% 62% 61% 30% 35% 51% 56% 66% 37% 23% Flooded Area 2000 ha 19,982 15,383 17,098 28,194 19,041 27,692 3,990 4,339 10,010 12,904 6,038 1,699 4,795 approximate return period year 3333333333333 2000 % 45% 21% 24% 34% 36% 40% 13% 6% 13% 23% 18% 8% 17% Flooded Area 2001 ha 20,175 10,583 1,627 1,652 1,692 8,682 1,533 1,692 4,028 2,653 523 732 2,349 approximate return period year 2222222222222 2001 % 45% 15% 2% 2% 3% 13% 5% 2% 5% 5% 2% 4% 8% Flooded Area 2002 ha 21,816 17,238 20,657 36,710 16,279 21,348 2,136 8,012 14,923 12,387 3,243 1,410 3,304 approximate return period year 6 10 6 10 10 5 5 10 5 5 5 5 5 2002floode % 49% 24% 29% 44% 31% 31% 7% 11% 20% 22% 10% 7% 12% Flooded Area 2003 ha 21,065 16,125 9,969 27,250 12,202 20,229 2,080 7,189 9,313 13,215 2,564 1,627 2,579 approximate return period year 7676666666555 2004 % 47% 22% 14% 33% 23% 29% 7% 10% 12% 24% 8% 8% 9% Flooded Area 2004 ha 26,020 15,137 30,880 48,384 23,764 30,750 5,328 9,127 21,929 18,904 7,097 3,096 4,942 approximate return period year 25 15 25 15 15 15 15 15 15 15 15 15 15 2004 % 59% 21% 43% 59% 45% 44% 18% 12% 29% 34% 21% 15% 18% Flooded Area 2007 ha 24,652 23,761 29,579 48,145 23,926 30,370 3,650 11,642 22,688 20,487 5,110 1,326 4,759 approximate return period year 30 30 30 30 30 30 30 30 30 30 30 30 30 2007 % 56% 33% 41% 58% 46% 44% 12% 16% 30% 37% 15% 7% 17%
average 2 year event 45% 18% 13% 18% 20% 26% 9% 4% 9% 14% 10% 6% 13% moderate (5-15year) 48% 23% 21% 39% 27% 30% 9% 10% 16% 23% 10% 8% 11% severe (>15yr) 62% 33% 49% 63% 51% 50% 20% 21% 37% 42% 34% 20% 19%
RANK flooding % flooded 2-yr event 1 5 7 4 3 2 11 13 10 6 9 12 8 % flooded 5-15-yr event 1 5 7 2 4 3 12 10 8 6 11 13 9 % flooded >15-yr event 2 9 5 1 3 4 11 10 7 6 8 12 13
1.2.3 Social Fabric JUSTIFICATION: ADB’s overarching goal is to fight poverty and consequently poverty incidence is an important criterion for any interventions. In addition, the envisaged MFF comes with some focus on the primary sector, not at last as agriculture provides the expected main benefits while employing still the majority of the Bangladeshi population.
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DETAILS FOR EACH SUB-CRITERION: Poverty Level The poverty level is based on primary data from the earlier quoted (Chapter 3) BBS census. We are using the upper limit for the lower poverty line based on the cost of basic needs (upper poverty line). This reflects how many people are poor. The group of hard-core poor is included in this figure and a subset.
Dependency on the Primary Sector The analysis is based on primary data from 2010 Household Income and Expenditure Survey (HIES). The reference unit is a dwelling unit. The primary sector dependency is expressed in three categories: agriculture/forestry/livestock, agricultural labor, fishery. The total number is expressed as percentage of the total number of dwelling units.
DETAILED TABLES:
CATEGORY SUB-CATEGORY Unit JRB1 JRB2 JLB1 JLB2 PLB1 PLB2 PLB3 PRB1 PRB2 PRB3 MRB1 MLB1 MLB2 UPoverty % 49% - 60% 49% - 60% 37% - 48% 37% - 48% 37% - 48% 37% - 48% 21% - 36% 37% - 48% 37% - 48% 21% - 36% 21% - 36% 21% - 36% 21% - 36% Lpoverty % 11% - 22% 23% - 32% 23% - 32% 23% - 32% 23% - 32% 23% - 32% 11% - 22% 23% - 32% 23% - 32% 11% - 22%4% or greate11% - 22% 11% - 22% Total Dwelling Unit no 177,316 159,245 209,784 218,324 144,721 183,163 132,133 153,375 180,137 146,039 140,190 57,543 124,381 Dwelling Unit of Agriculture/ Forestry/Livestock no 35,319 55,643 53,760 81,967 40,967 31,471 23,393 51,558 54,475 48,051 51,060 15,089 15,411 Dwelling Unit of Agri labour no 28,129 32,333 32,864 47,092 29,811 25,803 23,807 35,693 35,587 38,824 42,176 12,178 26,570 Dwelling Unit of FISHERY no 1,783 2,645 3,064 3,804 3,123 3,712 2,340 2,172 2,117 1,997 3,506 1,741 5,487 U Poverty Level % 60% 60% 48% 48% 48% 48% 36% 48% 48% 36% 36% 36% 36% Dependency on Primary Sector (% total dwelling % 37% 57% 43% 61% 51% 33% 37% 58% 51% 61% 69% 50% 38%
RANK poverty level 1133339339999 primary sector 12 5 9 2 7 13 11 4 6 3 1 8 10
CLASSIFICATION (POINTAGE) lower upper boundary 0.45 0.58 3322221221111 0.4 0.6 1223211223321
1.2.4 Ease of engineering JUSTIFICATION: Initial interventions need to be based on simple, straight forward engineering interventions for a number of reasons. Firstly, riverbank protection design can follow existing guidelines, while embankment design can be based on present best-practice, such as established in the International Levee Handbook (ILH, 2012). Secondly, easy implementation supports the quick initial success of a future program. Thirdly, initial implementation of riverbank protection does work during an emerging final planform and it is easier to accept some future adjustments to recently build low-cost work. Fourthly, the limited resources and time scale of a PPTA do not allow complicated design processes depending on costly, long supporting studies.
DETAILS FOR EACH SUB-CRITERION:
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Riverbank Protection Work in a sub-reach, contributing to large scale stabilization shall not depend on complicated engineering work. While long guiding geotextile bag revetments form the standard, offtake structures for distributaries are out of the ordinary. As example, the design for the Gorai offtake took multiple years and substantial resources. The ordinary construction receives one point, while out of the ordinary structures receive zero points. Embankments The standard is an embankment incorporating a road on the land side and a berm for temporary settlement towards the river. In addition, simple sluice gates for local drainage are considered. Complicated embankments would incorporate a number of offtakes or a large number of openings to let flow pass for example along the right bank of the Padma towards the coastal area. Points are awarded as above.
Other Difficult Structures Difficult structures relate mostly to the offtake regulators which requires specific structural designs. The work associated with a specific intake geometry is considered under riverbank protection. No additional structures are awarded one point, whereas additional difficult structures do not get any points.
DETAILED TABLES:
riverbank embankment other riverbank protection embankment other difficult structure protection difficult structure
JRB1 y y y normal conditions Kaijuri to Bagabari, potential regulator / fish pass u/s char JRB2 n n y confluence issues reclamation at confluence on potential additional loose char soils regulator / fish pass JLB1 n n y number of distributary number of offtake offtake old Dhaleswari and offtake geometries geometries Dhaleswari JLB2 y y y largely normal conditions largely normal floodplain offtake old Ichamutti PLB1 y y n normal conditions normal conditions no PLB2 n y n erosion resistant area, deep existing road, higher - check no PLB3 n y n stabilization of confluence normal conditions no PRB1 n y n Ganges barrage and normal conditions no confluence PRB2 n n y additional measures along around Faridpur, rest open Arial Khan offtake long reclaimed bank, for overland flow to south, PRB3 n n y response to Padma Bridge open for overland flow to regulator / fish pass RTW with higher v south, MRB1 n y y stabilization of confluence open for overland flow to regulator / fish pass south, MLB1 y y y conducive existing normal conditions existing embankment conditions MLB2 n y y Chandpur protection normal conditions regulator / fish pass
1.2.5 Complements existing work JUSTIFICATION: Completion of existing work means less efforts and higher potential rewards. This is the more true in economic terms, as existing work is treated as sunken cost, which do not reduce the economic feasibility.
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DETAILS FOR EACH SUB-CRITERION: Riverbank Protection Riverbank Protection of several kilometers in length is considered existing work. This could, for example, provide the backbone for reconstruction of embankments. In case there is existing work, one point is awarded, otherwise none.
Embankments Existing embankments provide potentially higher benefits at lower cost, if riverbank protection should be required. Consequently, existing embankments are awarded one point, while the non-existence of embankments receives none.
DETAILED TABLES:
riverbank embankment riverbank protection embankment protection JRB1 y y existing work at Kaijuri, 10 existing BRE km JRB2 y y existing work at Kaitola, 7 km PIRDP ring embankment is complete JLB1 n n no work, offtakes uncertain no embankment due to fund shortage JLB2 n n marginal work at Chauhali no major embankment PLB1 n y no work Dhaka SW embankment PLB2 y y natural protection some existing road close to bankline PLB3 n n marginal work at Munshiganj no embankment
PRB1 y n existing work at Rajbari no embankment PRB2 n n existing work at Faridpur no embankment useless if land reclaimed PRB3 y n Padma Bridge 12 km no embankment revetment MRB1 n n no work no embankment MLB1 y y existing work at Eklashpur, MDIP ring embankment 4.5 km complete MLB2 y n existing work at Chandpur, no embankment about 1.5 km
1.2.6 “No regret” JUSTIFICATION: Any work that does not match with a future planform results in a potential waste of funds.
DETAILS FOR EACH SUB-CRITERION: The only sub criterion is the assessment if there is a potential wastage as work built during the next decade (under an MFF program) could risk not match with the future desired planform.
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DETAILED TABLES:
no regret no regret JRB1 y existing straight channel and bifurcation to be maintained
JRB2 y existing western bankline channel for navigation JLB1 y existing straight channel and bifurcation to be maintained
JLB2 y existing eastern bankline channel dominant PLB1 y reclamation of land due to favourable planform PLB2 n potential char development alongside Mawa left bank PLB3 n downstream consequence of Padma Bridge uncertain PRB1 n unclear due to confluence PRB2 n river planform not yet developed for reclamation PRB3 n downstream consequence of Padma Bridge uncertain MRB1 n not clear with confluence MLB1 y bankline stable MLB2 n not clear with confluence
1.2.7 Safeguards JUSTIFICATION: Safeguards play an important role in the densely populated and highly exploited deltaic environment. Any major implications could stop interventions as planned. On a somewhat lower level, complicated interventions could require more time than available for PPTA preparation and as such also need to be avoided during the initial PPTA.
DETAILS FOR EACH SUB-CRITERION: Land Acquisition and Resettlement Land acquisition and resettlement in Bangladesh is complex due to the fractured small landholdings often with unclear land titles. This problem is unavoidable and required to be addressed for any construction work. We consider three levels of complexity, also depending on the extent of the work: low, medium, high, with points in descending order from 3 to 1. Normal resettlement involves a 50 m wide strip along the bankline and a 50 m wide strip for embankment construction. If the embankment length is limited to less than 20 km and runs through less populated areas, and if there is only limited riverbank protection the impact is low. Medium impact relates to longer embankments and/or riverbank protection. High impact relates to areas that require embankment works and riverbank protection, both of substantial length.
Environment There are no environmental sensitive areas in the areas under consideration. Consequently, environmental aspects focus also on potential effects beyond the boundaries. This is especially true for the southern sub-reaches, with contribute substantial fresh water to the coastal area and as such restrict salinity intrusion.
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DETAILED TABLES:
land acquisition environment land acquisition and environment and resettlement resettlement
JRB1 m m embankment and limited existing embankment, char riverbank protection implications JRB2 l l no embankment work, only low impacts due to largely limited riverbank protection existing work JLB1 h h both required distributary effects JLB2 h m both required normal impacts PLB1 m m full embankment but limited normal impacts riverbank proteciton PLB2 l l limited embankment work, limited impacts as no no revetment riverbank protection PLB3 h m both required normal impacts PRB1 h m both required normal impacts PRB2 h h both required flow to south impacted PRB3 h h both required flow to south impacted MRB1 h h both required flow to south impacted MLB1 l l existing work, minimal existing work, minimal impacts impacts h m both required normal impacts MLB2
1.2.8 Cost JUSTIFICATION: Individual tranches have only limited total budgets. This is required for not overloading the implementing agency but also from budgetary considerations of ADB’s pipeline. DETAILS FOR EACH SUB-CRITERION: Riverbank Protection Addressing two or three sub-areas is potentially more beneficial for achieving the overall goal than putting all investment of one tranche into one area. For this reason high investment is less beneficial than lower investment. As such points are given for low, medium, and high investment in descending order, starting with three points for low.
Embankments The same holds true for embankments.
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DETAILED TABLES:
riverbank embankment riverbank protection embankment protection
JRB1 l l normal new revetment, 10 normal new embankment, km already existing partly existing JRB2 l l normal new revetment, 7 km existing embankment already existing JLB1 h m substantial offtake work new embankment JLB2 m m limited offtake work new embankment PLB1 m m normal new revetment new embankment PLB2 l l erosion resistant area existing road can be converted to embankment PLB3 h m higher requirement revet- new embankment ment d/s of Padma Bridge PRB1 m m normal new revetment new embankment PRB2 h m normal new revetment, but new embankment offtake of Arial Khan PRB3 h h higher requirement revet- new embankment with many ment d/s of Padma Bridge openings MRB1 h h deep confluence with high new embankment with many velocities and weak soils openings MLB1 l l existing work, no revetment existing work, no embankment MLB2 h m deep confluence with high new embankment velocities
1.2.9 Benefits JUSTIFICATION: High benefits provide attractive investments.
DETAILS FOR EACH SUB-CRITERION: Directly A main consideration is that work in already protected areas is less likely to achieve lower incremental benefits than work in previously unprotected areas. As such this sub-criterion filters the potential for new investment. Direct benefits largely focus on the primary sector. The classification is only yes or no gaining one point for yes and zero points for no.
Additional Apart from primary sector benefits obvious additional benefits where visible were identified. Again points were given for yes and no.
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DETAILED TABLES:
directly additional directly additional
JRB1 y y restoration of BRE flow along west bank for navigation, reclamation of charland JRB2 n n existing scheme existing scheme JLB1 n y higher area dry season flow due to offtakes JLB2 y y increased due to reduced flood losses and dry season flow due to offtakes, incremental agri increases additional reclamation of charland PLB1 y y increased due to reduced flood losses and reclamation of charland incremental agri increases PLB2 y n increased due to reduced flood losses and reclamation likely only after ten years incremental agri increases PLB3 y n increased due to reduced flood losses and none incremental agri increases PRB1 y n increased due to reduced flood losses and none incremental agri increases PRB2 y n improvement of Faridpur flood situation none PRB3 n n open floodplain, reduced benefits none MRB1 n n open floodplain, reduced benefits none MLB1 n n existing scheme existing scheme MLB2 y n increased due to reduced flood losses and none incremental agri increases
1.3 MCA Weighting and Scoreboard The MCA combines all above criteria, and applies weighing factors to each criterion. We applied weighing factors at two levels: (i) primary interest and (ii) evening out of the number of sub-criteria. Firstly, the three vulnerability criteria (riverbank erosion, flooding, social fabric) were set to obtain higher marks, in order to allow addressing these more urgent problems at higher priority. Secondly, we applied weighing factors, so that each group of sub-criteria (primary interest and others) obtains the same maximum marks. In combination this means that the vulnerability criteria get a maximum of 90 marks. If there are three classification groups, for example high, medium, low, the weighing factor applied was 10 (3 sub-criteria * 3 points * 10 weighing factor = 90), if there are two classification groups (for example yes - no) the weighing factor is 15 (3 sub-criteria * 2 points * 15 weighing factor = 90). For the second group, the same weighing factors apply, only with the goal to reach a maximum of 30 points. The result is presented in (Table 1-2 ).
A sensitivity run, setting all criteria equal, confirms the same selection as obtained by above method. Furthermore, a very similar result was obtained during an initial discussion with ADB, BWDB and members of the PPTA team in September, however with less refinement and quantification of sub- criteria.
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Table 1-2: MCA scorecard
CATEGORY SUB-CATEGORY Unit JRB1 JRB2 JLB1 JLB2 PLB1 PLB2 PLB3 PRB1 PRB2 PRB3 MRB1 MLB1 MLB2 EROSION total (1973-2010) km² 2123312222211 recent (2007-2012) km² 2212112323312 future (2012-2020) km² 2233313333322 WEIGHT 10 60 50 60 80 70 30 70 80 70 80 80 40 50 FLOODING average (2-year) %3323331112112 based on radarsat mean (5-15 year) %3223231122111 images high(>15 years) %3233331122211 WEIGHT 10 90 70 70 90 80 90 30 30 50 60 40 30 40 SOCIAL FABRIC poverty %3322221221111 employment in agriculture %1223211223321 WEIGHT 15 60 75 60 75 60 45 30 60 60 60 60 45 30 Subtotal 210 195 190 245 210 165 130 170 180 200 180 115 120 ENGINEERING riverbank protection first? yes/no 1001100000010 INTERVENTION existing embankment yes/no 1001111100111 complicated structures yes/no 0000111100000 WEIGHT 10 20 0 0 20 30 20 20 20 0 0 10 20 10 COMPLEMENTS riverbank protection yes/no 1100010101011 EXSITING SCHEME embankment yes/no 1100110000010 WEIGHT 15 30 30 0 0 15 30 0 15 0 15 0 30 15 "NO REGRET" consist. w future planform yes/no 1111100000010 WEIGHT 30 30 30 30 30 30 0 0 0 0 0 0 30 0 EXPECTED COST riverbank protection (2.5M) l/m/h 3312231211131 embankment (0.5M) l/m/h 3322232221132 WEIGHT 5 30 30 15 20 20 30 15 20 15 10 10 30 15 SAFEGUARD expected social impact l/m/h 23112311111 3 1 IMPLICATIONS expected environm. impact l/m/h 2312232211132 WEIGHT 5 20 30 10 15 20 30 15 15 10 10 10 30 15 EXPECTED BENEFITS primary sector (agriculture) high/low 2112222221112 other (land-river transport) high/low 2122211111111 WEIGHT 7.5 30 15 22.5 30 30 22.5 22.5 22.5 22.5 15 15 15 22.5 Subtotal 160 135 77.5 115 145 132.5 72.5 92.5 47.5 50 45 155 77.5 GRAND TOTAL SUMMARY WEIGHT 107.5 370 330 237.5 330 325 297.5 202.5 262.5 257.5 250 255 330 197.5
Rank 1 2 11 2 5 6 12 7 8 10 9 2 13 winner winner winner winner winner winner
In conclusion the MCA indicates the following sub-reaches for potential initial investments (Table 1-3):
Table 1-3: Sub-reaches suitable for potential investment
River Sub-reach Division Jamuna Jamuna Right Bank 1 and 2 North West Jamuna Left Bank 2 North Central Padma Padma Left Bank 1 and 2 Meghna Meghna Left Bank 1 South East
1.4 Final Selection The final selection considers the relevance of the findings of the MCA. There are two main criteria to be considered: (i) overlap or conflict with existing or planned schemes, and (ii) “nothing to protect” during Tranche 1. With the focus of ongoing or planned investments, there are three sub-reaches that might be affected: (i) Rajbari where BWDB is building riverbank protection, and the Padma Bridge river training works planned at Mawa and Char Janajat. This means the PLB2 and PRB 2 sites will overlap with Padma Bridge river training works. “Nothing to protect” holds true for two of the winning sub- reaches: (i) JRB2, where there is little erosion at the PIRDP this moment and embankment set-back distances are quite large along unprotected banklines, and (ii) MLB1, where there is no erosion along the MDIP. Notwithstanding the lack of urgent protection, both sub-reaches should be covered under contingency measures during the first tranche, as their high ranking indicates the vulnerability and potentially viable investments. While the JRB2 site will have a clear focus on riverbank protection in support of an existing embankment line, MLB1 will have a clear focus on strengthening the flood embankment, which regularly is affected by “boiling” or seepage indicating a structural weakness.
Page 13 PPTA 8054: BAN- Main River Flood and Bank Erosion Risk Management Program
Considering the relevance of immediate interventions, the most attractive projects are listed in Table 1-4.
Table 1-4: Winning sub-reaches
River Sub-reach Division Jamuna JRB1 North West JLB 2 North Central Padma PLB 1
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ANNEX A2 : SUB-REACH DESCRIPTIONS
Page 15 PPTA 8054: BAN- Main River Flood and Bank Erosion Risk Management Program
Page 16 September 2013 A2 Sub-reach Descriptions
1 Jamuna Right Bank 1 –Jamuna Bridge – Shahjadpur Priority Project Name ID Upazilas (Unions) Area River Area Population Jamuna Right Bank 1 JRB1 3 (24) 582 km² 23.5 % 1,052,600
Bankline Total Erosion (1973- Flood extent Area Boro/Aman Population Density length 2010/2007-2012) (1998 / 2007) (total/floodplain) 37 km 1.52 km / 0.13 km 69% / 56% 65% / 37% 1810/2370
Situation The Jamuna Bridge guide bunds impose a straight channel downstream of the bridge flowing for about 15 km along the left bank of the braided belt (Sarker et.al 2011). As a consequence an about 15 km long and 5 km wide stable attached char has formed along the right bank, south of the Western Guide Bund. The straight channel bifurcates into a western and eastern branch at about Enayetpur, the eastern one presently being dominant. While the location of this bifurcation appears to be quite stable discharges vary in the two downstream channels. During the early 2000s hardly any dry season flow occurred along the right bank, while currently most dry season flow passes the channel along this bank.
The western flood plain was historically protected by the Brahmaputra Right Embankment (BRE) up to the Hurashagar/Baral River, upstream of the PIRDP. The last 10 km or so have been eroded from Kaijuri to the Hurashagar/Baral outfall. This erosion during the 1990s brought the once protected area back to the natural cycle of flooding and erosion, with substantial deposition of sand along the riverbanks (sand casting). The Hurashagar FCD project in this area became completely in operational (see FAP 2).
Figure from CEGIS morphology study for JMREMP
Page 17 PPTA 8054: BAN- Main River Flood and Bank Erosion Risk Management Program
Figure from FAP 2 report
Existing riverbank protection built from Kaijuri to Benotia in 2010 and 2011 has stabilized the riverbank and as such invited the cluster settlements of people living along the earlier BRE. It also stabilized the larger channel pattern and substantially reduced the dredging volume for the channel access to the important Baghabari Port (see Annex D of January 2013 report).
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250,000 Mohanganj to Kaitola 200,000 average Mohanganj to Kaitola 150,000
100,000
50,000
-
Future Scenarios The area at Enayetpur has come under erosional attack during the 2012 dry season with the Enayetpur spur at the brink of collapse from erosion. As the existing riverbank protection (spur) in this area is not reliable, substantial infrastructure is at risk, notably Enayetpur with a large hospital complex from erosion and the area behind the BRE from immediate flooding once a breach occurs. The situation is comparable to the PIRDP in the early 2000s when the flood embankment was at risk of immediate erosion.
Enayetpur Spur, dry season 2012/13 2012/13 (note absence of toe protection) and riverbank erosion upstream
Future channel planforms downstream of the bifurcation at Enayetpur can consist of one or two channels. The initial morphological study for the lower Jamuna reach (Annex C, January pre- feasibility report) indicates that the present two-channel system with one large char provides the
Page 19 PPTA 8054: BAN- Main River Flood and Bank Erosion Risk Management Program
overall best solution and in terms of future river management (or stabilization) efforts the most pragmatic approach.
Existing Works BWDB has built two RCC spurs at Betil and Enayetpur, which were rehabilitated two times from ADB flood damage repair funds (after the 2004 and 2007 flood), but which are not stable for major river attack as experienced at this moment. BWDB, under JMREMP, has built 10 km of riverbank protection from Kaijuri towards the Hurashagar River. Some of this work shows local geotechnical failure (slip circles) and is presently (dry season 2013) repaired at cost of 1.5 Crore. Three LGED small scale projects are situated in this area.
Project Concept This sub-project incorporates three BWDB priority projects: (i) riverbank protection along the right bank of the bifurcating channel from upstream of Enayetpur towards Kaijuri, (ii) riverbank protection upstream of the Hurasagar to close an existing gap, and (iii) reconstruction of the BRE and Hurashagar FCD embankment from Kaijuri to Shahjadpur
Tranche-1 • Reconstruction of the BRE for some 12.5 km along the Jamuna incorporating a road and rehabilitation of the embankment along Hurashagar/Baral (9.5 km) • 1 km of riverbank protection downstream of the existing protection towards the Hurashagar/Baral • Different regulators for water management (including rehabilitation of existing structures) • Provision for the adaptation of existing work and for immediate stabilization of the Enayetpur spur BENEFITS This work will substantially reinstate the original BRE and allow reaping initial benefits from the destroyed Hurashagar FCD project (see following flood maps from 1987 “with Hurashagar FCD” and 1998 “without Hurashagar FCD”, which shows that less area was flooding in 1987 specifically at the Hurashagar FCD project. Closing the BRE gap along the Jamuna will generate benefits beyond the Hurashagar FCD by reducing the flood levels overall. The road connection along the Jamuna bank will be complete and connect the densely populated area along the bank with Jamuna Bridge and Shahzadpur via Kaijuri
Tranche-2 • Rehabilitation of the remaining embankment from Baghabarito Shazadpur along the Kortoa river (4 km) and construction of the road from the Jamuna embankment to Baghabari and Shahzadpur • About 11 km of priority riverbank protection to stabilize the riverbank from the upstream bifurcation towards Kaijuri. This means Enayetpur will be protected from erosion and flooding and erosion and embankment breaches will be prevented in future. In addition, the off-take of the western Jamuna channel providing the main access to the Baghabari Port will be stabilized. Potentially some distance will be excavated or dredged during construction of the upstream riverbank protection through low lying charland. This creates a substantial amount of excavated/dredged material, which can be used to fill in the bankline channel between Enayetpur and Betil for reclamation purposes. • There are provisions for adapting existing riverbank protection to greater river depth BENEFITS 1 Hurashagar FCD project: The Hurashagar FCD project will be fully operational with full flood benefits. The road connection to Baghabari (via ferry) and Shahzadpur will provide impetus for increased economic activities. 2 Enayetpur area: The erosion of land including the risk of loosing the Enayetpur hospital will be avoided. As such the riverbank protection stabilizes the existing embankment in a similar manner as
Page 20 September 2013 A2 Sub-reach Descriptions
done by the original JMREMP work at the PIRDP.
Flood comparison prepared by CEGIS
Optional work in this area, depending on morphological study, economic feasibility, and availability of funds, are: • Provisional protection of char head for bifurcation stabilization (depending on morphological confirmation) with the aim to create an all-year-round navigable channel towards Jamuna Bridge. • Potential future construction of BRE over the attached char from Jamuna Bridge to Enayetpur, providing a reclamation potential of around 50 km² of land, if required supported by catkin plantation for accelerated sedimentation and soil fertility. • Potential construction of 5 km of additional riverbank protection and adaptation of the existing 10 km to expected greater river depth associated with a more stable channel
Intervention Elements List by type Description (Location, dimensions or quantity) Infrastructure TRANCHE-1 1.RBP 1 km at Benotia Adaptation and Enayetpur spur stabilization 2. EMB 23 km for reconstruction of BRE and Hurashagar FCD scheme 3. Other for water management 4 new regulators with 11 vents in total (1*1 vent, 1*4 vent, 1*6 vent) and rehabilitation of 2 existing 4 vent regulators Infrastructure TRANCHE-2 1.RBP 11 km at Enayetpur for protection and stabilization of the bifurcation LS adaptation work to greater river depth 2. EMB 4 km of embankment along Kortoa river and 13 km of road construction from Jamuna to Shahzadpur 3. Other Buoys for navigation and fish protection along revetment work
Page 21 PPTA 8054: BAN- Main River Flood and Bank Erosion Risk Management Program
Intended Benefits (+) and Known Potential Adverse Impacts (-) + Description Type - (impacted location, activity or asset; timing, extent or magnitude) ? Reduced flood + Whole area from damage (i) Rehabilitated embankments (BRE and Hurashagar FCD project) (ii) Securing BRE at the Enayetpur area Reduced erosion + Whole bankline through stabilized river course Navigation + More stable channel along protected bank with increased draught Dramatically reduced dredging cost Land reclamation + Downstream part of Enayetpur char secured Water + Improved conditions for HY aman and dry season irrigation after Management reconstruction of BRE Communication + Improved access in case a dedicated national highway standar road is built along the embankment from Beira to Nagarbari and beyond Land - Associated with original BRE embankment – about 1 km² (20km*50m) acquisition/loss floodplain land Resettlement - To be confirmed Fisheries ? Geotextile bag revetments provide shelter, attached chars potential spawning ground, protection from floating nets Improved operation of regulators following GIZ biodiversity project (at Pabna)
Supporting Studies River surveys by BWDB and the PPTA team Surveys Flood plain surveys along the Hurashagar and Kaijuri to Shariatpur Char-land Study Investigation of deposition rates of the char opposite of the Hurashagar/Baral outfall and upstream between Enayetpur and Jamuna Bridge River Modeling & 1-D HEC RAS modeling of flow patterns to determine the minimum width of a Analytical Approach single channel river solution Flood Modeling Scenario 1: restoration of Hurashagar FCD embankment from Kaijuri to Benatia along the Jamuna, Benotia to Baghabari along the Hurashagar/Baral, and Baghabari to Shahzadpur along the Karatoa River Scenario 2: loss of flood protection in the Enayetpur area due to erosion and breach of the embankment EIA/SIA Environmental baseline and impacts of above works Resettlement 100% census and IOL, 20% SES for embankment and 2 km of riverbank protection
Version change log (latest first) Version created Change date Changes made + reasons for changes by change 10 May 2013 5.0 Updated for final report - ko 26 Feb2013 4.0 detailed work layouts Tranche-1 and 2 – ko (MZ review) updated maps 6 Feb2013 3.0 Finalization with more detailed work layouts and maps– ko 3 Oct 2012 2.0 Full description entered – ko 25 Sep 2012 1.0 Initial version of project description – slb
Maps: Infrastructure Flood and erosion on satellite image Flood and erosion on DE
Page 22 September 2013 A2 Sub-reach Descriptions
Program Interventions Restoring and Securing the Brahmaputra Right Embankment: Tranche-1 and 2 Interventions are planned in Tranche-1 and Tranche-2 and lead to a systematic development of flood protection and riverbank stabilization. The following figure summarizes the interventions.
Tranche 2 11km riverbank Tranche 1 protection • 12.5km new emba- nkment with road • 9.5 km embankment rehab • 4 sluice gates • 1 km riverbank protection Tranche 2 • 6km embankment with road • 10 km road
Page 23 PPTA 8054: BAN- Main River Flood and Bank Erosion Risk Management Program
Purpose: The purpose of the downstream work started in Tanche-1 is to restore the eroded Brahmaputra Right Embankment (BRE) along the Jamuna River and to rehabilitate the degraded flood embankment along the Hurashagar River. The embankment along the Hurashagar is basically completely eroded for the downstream half, while there is some low and embankment left along the upstream half. There are two existing 4-vent sluice gates in the embankment along the Hurashagar, which will be rehabilitated and extended. The embankment along the Jamuna will be provided with a road. The existing 10km long riverbank protection will be extended by one kilometer in downstream direction, in order to secure the new BRE. There will be two new sluice gates, one at Kaijuri to drain the Hurashagar and one north of Vatpara to allow flood season inflow into the relic Hurashagar channel. In Tranche-2 the remaining 6 km of embankment will be built with road, plus the road will be built at the 10km of Tranche-1 embankment along the Hurashagar. Annex F describes the technical designs.
Tranche 2 6km embank- Tranche 1 ment with road 12.5km new 10 km road embankment with road 9.5 km embankment rehab 4 sluice gates
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The embankment crest level is 1.5 m above 100-year flood level along the Jamuna and the downstream 5km of the Hurashagar from where it transitions to 1 m freeboard at Baghabari (and in Tranche-2 to Shahzadpur). The 100-year flood levels are: Kaijuri: 13.90 m+PWD Hurashagar outfall, Verakhola: 13.30m+PWD Baghabari 13.60m+PWD
Uncertainties pertaining to the exact assessment of future water levels as a consequence of climate change are incorporated into the design of the embankments. The proposed cross section allows the increase of the crest level without additional land acquisition or disturbing the road.
The new regulators are planned at the following locations:
Location Catchment area (Ha/ventage) Location [Northing Outfall River and Easting] Lochna Existing (4vent, add 2 vent); 1750 ha 461392E; 665068N Hurasagar/Baral Gala Existing (4 vent; add 4 vent) 3550 ha 465114E; 662557N Hurasagar/Baral Kaizuri, Gopalpur 5570 (6 vent-new) 468742E; 673594N Jamuna Gudhibari 850 (1 vent-new) 467619E; 671008N Jamuna
The estimated quantities for Tranche-1 work are:
Structure Details Volume Comments New embankment 12.5 km 1,880,000m³ sand Sand-fill dredged Rehab. embankment 10.5 km from river Sluice gates 4 Nos,13 vents Structural concrete: 2225 m³ Riverbank protection 1 km at Verakola 125kg geobags: 380,000 Nos Geotextile bag Concrete blocks: 10,900m³ revetments
The new embankment line will reduce the flood damages in the area. Selected historic damage data are shown in the following graph (more details are provided in Annex D).
The total area of JRB-1 can be broken down as follows:
Land Type Area (ha) Per Cent of Total (%) Gross Project Area 58,209 Adjusted Project Area protected by Embankment (APA) 41,067 100 Settlement Areas 8,855 22.0 Ponds, streams, other non-agricultural land 2,213 5.5 Net Cultivable Area (NCA) 30,000 73
Most of the land is low lying and the area would be totally inundated during the 100-year water levels.
Page 25 PPTA 8054: BAN- Main River Flood and Bank Erosion Risk Management Program
14 JRB1 12
10
8
6 Elevation (m) 4
2
0 0% 20% 40% 60% 80% 100% Per Cent Less Than
The flood modelling (Annex D) provides the following details for different flood characteristics. The 1998 flood is a high flood, the 2007 is moderate, and the 2003 is a low flood.
Areas (in ha) 1998 2003 2007 Adjusted project area (APA) 41,067 41,067 41,067 Settlement area 8,855 8,855 8,855 Other non-agricultural land 2,213 2,213 2,213 Net cultivable area (NCA) 30,000 30,000 30,000 F0 land (including flood free) 2,737 12,673 8,164 F1 land 36 117 135 F2 land 2,196 2,313 2,880 F3 land 15,516 12,024 12,105 F4 land 10,359 3,825 7,461 Total flooded cultivable area 28,107 18,288 22,581 Per cent of NCA flooded (%) 91% 59% 73% Per cent of APA flooded (%) 74% 50% 60%
After construction of the complete embankment in Tranche-2 the land type would change as follows:
Change in area (ha) 1998 2003 2007 F0 land (including flood free) +6,336 +6,642 +5,607 F1 land +2,286 +999 +2,052 F2 land +2,772 +864 +1,674 F3 land -5,274 -6,705 -5,184 F4 land -5,985 -1,647 -3,969 Total flooded cultivable area -5,283 -6,237 -5,013 Per cent of NCA flooded (%) -17% -20% -17% Per cent of APA flooded (%) -13% -15% -12%
The riverbank protection suggested for the area at Enayetpur in Tranche-2 secures the existing BRE. Without this protection there is the risk of an embankment breach leading to large scale flooding:
Area (ha) Breach – WO Breach – WP Change in F0 land +2,241 -11,772 Change in F1 land +1,026 -558 Change in F2 land -2,826 -810 Change in F3 land -6,543 +4,995 Change in F4 land +6,102 +8,145
For assessing economic benefits the 2007 flood was selected as representative moderate flood. Benefits were derived as follows:
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(i) Selection of the inundated area (in ha) for with and without project scenario (refer to above tables)
F0 F1 F2 F3 F4 With project 13,771 2,187 4,554 6,921 3,492 Without project 8,164 135 2,880 12,105 7,461 Incremental 5,607 2,052 1,674 -5,184 -3,969
(ii) Selection of area suitable for cropping (73.1%)
F0 F1 F2 F3 F4 With project 10,060 1,598 3,327 5,056 2,551 Without project 5,964 99 2,104 8,843 5,450 Incremental 4,096 1,499 1,223 -3,787 -2,899
(iii) Identification of crop intensity for different land types
F0 F1 F2 F3 F4 With project 227.1 198.0 172.1 177.5 0.0 Without project 227.1 154.0 170.1 177.5 100.0
(iv) Identify the total cultivated Area (ha)
F0 F1 F2 F3 F4 With project 22,850 3,164 5,724 8,974 0 Without project 13,547 152 3,579 15,696 5,450 Incremental 9,304 3,012 2,145 -6,722 -5,450
(v) Identify the construction sequencing and the benefit development
Tranche 1 Tranche 2 Tranche 3 Total Length [km] 23 6 0 29 Phasing [%] 79.3 20.7 0.0 100.0
The land improvement for largely agriculturally based activities applies to the area suitable for cropping with special focus on flood mitigation and drainage but also irrigation (mostly maintaining sustainable irrigation infrastructure during times of flooding). To this end it is associated with the land types, which is more intensively agriculturally used after implementing the project. Improvements in flood mitigation are commonly associated with the reclassification of the type of land to the next higher class, or lifting it to a land type with less inundation. While this applies for all classes from F3 to F0, in this special case both deeply flooded land types, F3 and F4, reduce substantially for the with-project scenario. The total F0 to F2 land are is around 15,900 ha with project as opposed to 8,300 ha without project, or a change of 7,600 ha. The figures for land suitable for cropping are 11,600 ha with project as opposed to 6,000 ha without project, translating into an increase of 5,600ha.
The improvement in land type translates into improvements in living conditions at household level. The average population density is 2380 persons per km² on the floodplain. Multiplying this figure with the total area of improved land types (F0 to F2 land) for 7,600 ha results in a flood risk reduction for 180,000 persons at the end of the program.
A 1.52 km wide strip of land eroded from 1973 until 2012 and a 0.13 km strip of land from 2007 until 2012. This translates into annual average erosion rates of 39 m over the whole period of 39 years and 26 m over the last five years of that period.
Page 27 PPTA 8054: BAN- Main River Flood and Bank Erosion Risk Management Program
For estimating the economic feasibility the benefitted area erosion data have been estimated mimicking observed erosion patterns, which come and go periodically. To this end 5-year erosion patterns followed by 5-year without erosion are assumed. In order to estimate benefits, and in line with the program concept to prevent predicted erosion in key areas, the work is assumed to prevent erosion starting from its completion date. This means that works starting in Tranche-1 prevents erosion from year 4, works starting in Tranche-2 prevents erosion from year 7, and work starting in Tranche-3 prevents erosion from year 10. The assumed erosion rate for JRB-1 is 125 m per year, which reflects local peak erosion rates correspondingto the total average erosion rate over the last 5-years. As such 1 km of protection saves 12.5 ha of land annually from erosion or 62.5 ha over 5 years. This is the same after 10-years, assuming that the erosion rate stops during the second cycle. The following table summarizes the aggregate erosion losses in ha for each 5-year period of the project implementation.
location Length Annual Work 5- 10- 15- 20- 25- 30- [km] erosion [m] start years years years years years years Benotia 1 125 year 1 25 62.5 87.5 87.5 113 150 Enayetpur 11 125 year 4 550 688 1238 1375 1925
Related to the physical work, there is land-acquisition and resettlement impact. The following figure shows the number of agricultural plot users, affected households and land requirements for different sections. It also indicates potential locations of construction camps.
Length (km) Land acquired (ha) Affected Households RBP 12 34.82 504 EMB 29 95.1 1493 Structures 4.21 0 Total 134.13 1997
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2 Jamuna Right Bank 2 –Pabna Project Name ID Upazilas (Unions) Area River Area Population Jamuna Right Bank 2 JR2 3 (29) 915 km² 21.1 % 915,200
Bankline Total Erosion (1973- Flood extent Area Boro/Aman Population Density length 2010/2007-2012) (1998 / 2007) (total/floodplain) 66 km 0.31 km / 0.06 km 36% / 33% 19% / 46% 1000/1270
Situation Number of erosion Total Erosion Years [m] 0 10 20 0 1000 2000 The western Jamuna channel flows as dry season meandering and anabranched channel along the eastern bankof the JRB- 2 before it turns east at the confluence with the Ganges. This channel causes some bank erosion in this sub-reach specifically at Nagarbari and downstream (lower part in figure on the left). There is little indication about severe riverbank erosion along the Ganges left bank up to the location of the planned Ganges barrage.
The western Jamuna channel is an important navigation route to the Baghabari Port, which supplies the whole northwestern Bangladesh with fertilizer and fuel. Dredging volumes have recently reduced dramatically after construction of riverbank protection upstream of the Hurashagar in the area Kaijuri to Benotia (see future scenarios).
The PIRDP, covering the area is expected to remain an area of main agricultural production. BWDB has tried through continuous efforts from the mid-1990s to 2011 (CAD and JMREM projects) to arrive at sustainable participatory water management, however with limited success. Reasons are the complicated slow responding irrigation network, a somewhat unreliable water supply on time, and the overall difficulty to implement a recurrent participatory planning process. As the area experiences a largely reduced flood and erosion risk (see flooded areas on the left), there is some potential for increased agricultural output.
Future Scenarios
Page 29 PPTA 8054: BAN- Main River Flood and Bank Erosion Risk Management Program
Jamuna and Ganges, the eastern and southern boundary will exhibit their dominant influence on this area in future. Given that the Ganges barrage could provide for larger scale stability of the area, the jibbery Jamuna morphology will influence the banklines in future. Given that much of the bankline is yet unprotected (roughly 25 out of 35 km) future vigilance to the erosion risk of the flood embankment is required. In addition, riverbank stabilization will further reduce the dredging volumes in the area. While the dredging volume along the protected bank downstream of the Hurashagar (Mohanganj to Kaitola) has dropped to less than 50% of the previous average, the dredging quantities of the unprotected area downstream remain unchanged. It is also evident that the area downstream is less affected (only around half of the time), which makes the investment into dredging cost reduction upstream more economic.
250,000 Mohanganj to Kaitola Dredging Volumes along JRB-2 total Awalbad Dolar 200,000 average Mohanganj to Kaitola 150,000 average Awalbad to Dolar
100,000
50,000
-
Longer-term Erosion prediction for the downstream bank (CEGIS 2007) confirms a high latent risk. If the erosion approaches the embankment with the risk to breach it, the situation would become similar to the situation in the early 2000s, when the PIRDP was at risk from erosion in the Hurashagar/Baral – Kaitola area. However, it is not expected that this development would take place immediately, however could arise during the next decade.
710000
bankline 2006 690000 predicted 2020 (50%)
670000
650000 455000 465000 475000 Easting (m)
Existing and Planned Works
Page 30 September 2013 A2 Sub-reach Descriptions
The flood plain is lower but protected through a ring embankment of the Pabna Irrigation and Rural Development Project (PIRDP). This embankment has been protected along 7 km of bankline (immediately downstream of the Hurashagar river) with riverbank protection works through JMREMP. The following around 5 km are passively protected as the river is deflected towards the east (center of the braided belt) near Kaitola, supported by and a large setback distance to the existing embankment. The embankment was strengthened during the mid-2000s as part of the ADB supported flood damage rehabilitation after the 2004 flood. One LGED small scale project is situated in this area.
Project Concept There is no immediate need for protection as the PIRDP has functional protection. The confluence between Ganges and Jamuna needs further studies before any work can be done in this area. As such interventions would start earliest in Tranche-2, more likely in Tranche-3.
Tranche-2 or 3 provisions • Riverbank protection downstream of Nagarbari, potentially along Ganges • The central char is intended to be left unprotected to maintain natural river processes • Potential strengthening of embankment with road
Optional, depending on economic feasibility and availability of funds • Reclamation of attached char at Ganges – Jamuna confluence with potentially 50 km² of land through a guided process of accelerated siltation – making use of katkin plantations as piloted in Bhuapur in the 1990s.
Intervention Elements List by type Description (Location, dimensions or quantity) Infrastructure TRANCHE-2 or 3 (provisional) 1.RBP Provisional allocation of up to 5km along the southern Jamuna bankline 2. EMB Provisional strengthening of existing embankment including construction of national standard road. At the confluence lost floodplain land could be reclaimed and embanked with round 20 km of new embankment. 3. Other Potentially complex confluence stabilization considering with and without Ganges Barrage scenarios Sluice gates/regulators, fish passes Buoys for navigation and fish protection along revetment work
Intended Benefits (+) and Known Potential Adverse Impacts (-) + Description Type - (impacted location, activity or asset; timing, extent or magnitude) ? Reduced flood damage + No change due to existing embankment, however expected change in overall risk if embankment is strengthened Reduced erosion + Bankline from Kaitola to Ganges Navigation + More stable channel along protected bank with increased draught Land reclamation + Potentially 50km² if the area at the confluence becomes stabilized Water Management + Participatory regulator management for optimized rice-fish production Communication + Improved access in case a dedicated national highway standard road is built along the embankment from Beira to Nagarbari and beyond Land acquisition/loss - Associated with embankment widening in case of road construction Resettlement - To be confirmed Fisheries + Geotextile bag revetments provide shelter, central river chars potential spawning ground
Page 31 PPTA 8054: BAN- Main River Flood and Bank Erosion Risk Management Program
The GIZ supported biodiversity project is actively supporting the participatory management of an existing regulator in the downstream area
Version change log (latest first) Version created Change date Changes made + reasons for changes by change 1 Mar 2013 3.0 Description updated and expanded – ko 6 Feb 2013 3.0 Moderately updated – ko 3 Oct 2012 2.0 Full description entered – ko 25 Sep 2012 1.0 Initial version of project description – slb
Maps: Infrastructure Flood and erosion on satellite image Flood and erosion on DEM
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3 Jamuna Left Bank 1 – Tangail Project Name ID Upazilas (Unions) Area River Area Population Jamuna Left Bank 1 JL1 3 (32) 787 km² 8.8 % 1,138,700
Bankline Total Erosion (1973- Flood extent Area Boro/Aman Population Density length 2010/2007-2012) (1998 / 2007) (total/floodplain) 21 km 2.46 km / 0.06 km 42% / 41% 48% / 41% 1450/1590
Situation The east bank of the lower Jamuna is a very erosion prone area since the time of construction of the Jamuna Bridge (data series covering 13 years from 1994 to 2006, CEGIS, 2007).
Number of erosion Total Erosion Years [m] 0 10 20 0 1000 2000
The Jamuna flows as straight channel downstream of Jamuna Bridge for about 15 km along the left bank. This channel causes some bank erosion in this sub-reach. The channel bifurcates into a western and eastern branch, the eastern one presently being dominant. The location of this bifurcation appears to be stable.
There are two to three distributaries of the Dhaleswari system including the main Dhaleswari river at the southern boundary of this sub-reach. The offtakes have been studied in detail for the Buriganga Restoration Project, providing the rivers around Dhaka with fresh water. Sediment aspects have not been considered but are important for the long-term stability of the Dhaleswari.
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The floodplain is vulnerable to flooding for some distance from the river. The area around Tangail is somewhat protected from the Compartmentalization Pilot Project (FAP20) implemented during the second half of the 1990s.
Future Scenarios As a consequence of the asymmetric location and restrict width of the Jamuna Bridge Guide Bunds, the
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Jamuna flows as single channel along the eastern bank of the formerly braided corridor in this area. It is expected that this will continue in future limiting the amount of riverbank erosion. The observed dry season channel is rather narrow in places, around 2.5 km, which is beyond the minimum hydraulic width for carrying major flood flows. The channelization concept uses 4.km as minimum width. To this end it will be required to give the river some room in this area, so that future flows can pass without problems. This accepts that low temporary chars can form in this area somewhat resulting in an alternate bar pattern.
One important project scenario, the opening of the distributaries providing water to the river system up to Dhaka was studied by IWM in 2003 and arrives at substantial benefits for the whole area, especially to improve environmental flows and navigation during the dry season. The study proposed to open the Buriganga-Turag and Shitalakhya river system to dry season flow through the New Dhaleswari (south of Jamuna Bridge)-Pungli-Bangshi-Turag-Buriganga (172km). The Dhaleswari South offtake-Barinda-Bangshi-Sout-KarnataliKhal, Buriganga (140km) was discarded as too difficult and not delivering water to the Turag. The flow requirements were (i) 3.9 m draft for class-I navigation, (ii) >4mg/l dissolved oxygen, (iii) mitigate tidal effects, which requires 250m³/s of dry season discharge.
Apart from riverbank protection and an offtake a limited amount of channel (dredging, loop cuts) and bridge improvements were identified specifically for navigation. A broad variety of benefits was identified: (i) saving of crop losses due to floods, (ii) increased cropping intensity and yields, (iii) increased fish production, (iv) increased navigation, (v) saving due to improved health and reduced water borne diseases, (vi) saving of flood damages to dwellings, industries and public infrastructure, (vi) tree plantation to enhance environmental condition. The economic capital cost amount to BDT 5,341,749,000 (roughly USD 90 Million) with an EIRR of 23% and a NPV of BDT 4,193,225,000 (roughly USD 70 Million). The work has not been implemented partly due to some discussion on the merits of an offtake regulator.
Future Works As the single Jamuna channel is largely stable and requires some room, there is not much scope for riverbank protection. However, for dry season water management purposes several offtakes from Jamuna Bridge to the Dhaleswari River need some defined design including approach channel and
Page 35 PPTA 8054: BAN- Main River Flood and Bank Erosion Risk Management Program offtake geometries. This is the more challenging as the river channel exhibits an unstable pattern of dry season chars and shoals.
It is clearly beneficial for the large area, not only in terms of flood management to provide stable offtake geometries for the distributaries along the Jamuna left bank.
Existing and Planned Works The Tangail Compartmentalization Pilot Project is situated in this reach as well as two LGED small scale projects. No riverbank protection has been constructed in this reach
Project Concept The work in this area is not priority work and depends on future studies and availability of funds. Potential works could include: • Riverbank protection in places to stabilize the Pungliofftake geometries. • Construction of some embankments around offtakes; likely of reduced height due to favorable topography
Intervention Elements List by type Description (Location, dimensions or quantity) Infrastructure TRANCHE – 2 or 3, provisional 1.RBP Riverbank protection at the offtake geometries for the distributaries of the Dhaleswari system If morphologically required protection of char head for bifurcation stabilization 2. EMB Probably limited in length and height, mostly around offtakes
Intended Benefits (+) and Known Potential Adverse Impacts (-) + Description Type - (impacted location, activity or asset; timing, extent or magnitude) ? Reduced flood damage + Whole area Reduced erosion + Whole bankline Navigation + More stable channel along protected bank with increased draught Land reclamation + None Water Management + Improved dry season flow in Dhaleswari for boro irrigation and cleaning the Buriganga at Dhaka Land acquisition/loss - Associated with embankment and riverbank protection Resettlement - To be confirmed Fisheries ? Geotextile bag revetments provide shelter, attached chars potential spawning ground
Version change log (latest first) Version created Change date Changes made + reasons for changes by change 10 May 2013 5.0 Reviewed for final report - ko 1 Mar 2013 4.0 Description expanded – ko 3 Oct 2012 2.0 Full description entered – ko 25 Sep 2012 1.0 Initial version of project description – slb
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A2 Sub-reach Descriptions
4 Jamuna Left Bank 2 – Aricha Priority Project Name ID Upazilas (Unions) Area River Area Population Jamuna Left Bank 2 JL2 6 (48) 1212 km² 31.9 % 1,104,800
Bankline Total Erosion (1973- Flood extent Area Boro/Aman Population Density length 2010/2007-2012) (1998 / 2007) (total/floodplain) 56 km 2.59 km / 0.12 km 62% / 58% 32% / 44% 910/1340
Situation The east bank of the Jamuna is erosion prone since the construction of Jamuna Bridge (see JRB-1). The presently dominant eastern Jamuna channel flows as meandering (dry-season) channel along the bank leaving a larger attached char of more than 10 km in length in the upstream part of the project, between Dhaleswari and GhiorKhal (old Dhaleswari) offtake. This eastern Jamuna channel erodes its riverbanks at Chauhali and Zafferganj since several years putting both growth centers at the risk of extinction. The upazilla Chauhali has lost most of its floodplain land and nowadays consists mostly of a
river and char environment.
Apart from the main Dhaleswari river offtake, which consists of several offtake channels within an approximately 5 km bankline reach another distributary exists notably the GhiorKhal near Daulatpur. Both are vital to provide water to the river system around Dhaka (see map in JLB-1)
The flood plain is lower and prone to excessive flooding during higher floods (see figure in JLB-1).
Future Scenarios It can be expected that eastern and western
Jamuna channel will be separated by a more stable bankline char in future, however, it is not clear if either 2006 channel can break through the char to join the 690000 predicted other channel. 2020 (50%) Both channels experienced alternating times of nearly no dry season flow with the eastern channel 670000 presently carrying the majority of the water. During the flood season, however the discharge appears to be much more evenly distributed. The dry season variability results from the changing 650000 460000 470000 480000 bifurcation morphology upstream of the Easting (m) Dhaleswari and has implications on the dry season navigation. Given that little riverbank protection was built in this area, the future scenario without protective measures predicts quite substantial riverbank erosion the order of kilometers (see next figure from CEGIS, 2007).
Existing and Planned Works BWDB has provided 2 km of riverbank protection at Chauhali in 2011/12, which was largely destroyed during the 2012 flood.
BWDB plans an about 35 km long embankment along the riverbank from the Dhaleswari (Nagarpur upazila) to Aricha for two FCD projects, namely the Nagarpur-Chauhali and the Jamuna-Padma left bank Project (shown in the following figures, from FAP-3 documents). These two projects go back to the FAP-3 planning in the early 1990s recognizing the vulnerability of the area to flooding and flood damages
Page 37 PPTA 8054: BAN- Main River Flood and Bank Erosion Risk Management Program
figures from FAP-3 report
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Three LGED small scale projects are situated in this area. The areas at Chauhail and Zafferganj were identified by BWDB as priority areas for riverbank stabilization during the preparatory phase of this MRP PPTA in 2011.
Project Concept This subproject incorporates three BWDB priority projects: (i) riverbank protection along vulnerable reaches with a view to work towards river stabilization, (ii) strengthening of the existing 12 km long embankment from Aricha to Zionpur via Zaffarganj and extension to the Dhaleswari, (iii) provision of defined Dhaleswari and Ghior Khal offtake for dry and flood season flow including navigation. The central char is intended to be left unprotected to maintain natural river processes and to not disturb the established char societies. The project concept depends on further studies during Tranche-1.
Tranche-1 • Priority riverbank protection at Chauhali (about 5 km) and Zafferganj (about 2 km) to stabilize critically eroding reaches along the upazila headquarters • Pilot testing of guided, accelerated charland accretion of a suitable attached char through catkin plantation Tranche-2 • Extension of existing riverbank protection in upstream and downstream direction Chauhali including Dhaleswari offtake (around 3km) with the purpose of stabilizing the attached char in that area Zafferganj area (2 km) • Stabilization of attached char through guided, accelerated siltation (plantation of catkin as piloted in Bhuapur in the 1990s and other measures) with the purpose of reclaiming around 30km² of lost floodplain land • Rehabilitation of 12 km of existing embankment Tranche-3 • Extension of existing riverbank protection in upstream and downstream direction Chauhali including Dhaleswariofftake (around 5km) with the purpose of stabilizing the attached char in that area Zafferganj area (2 km)
Page 39 PPTA 8054: BAN- Main River Flood and Bank Erosion Risk Management Program
• Optional offtake geometry of Dhaleswari likely distinguishing dry season and flood season offtake • Offtake geometry at GhiorKhal • Embankment rehabilitation and link embankment from Dhaleswari to Aricha (total length around 17km) • Local placement of navigation buoys with combined navigation / fish protection purpose
Intervention Elements List by type Description (Location, dimensions or quantity) Infrastructure TRANCHE-1 1.RBP Around 7 km initial left bank stabilization: 5km at and 2 km at Zaffarganj 2. Other Pilot test of guided, accelerated charland siltation (catkin and supporting measures) Infrastructure TRANCHE-2 1.RBP Extension of existing protection Around 3 km at Chauhali, Around 2 km at Zaffarganj 2. EMB Rehabilitation of 12 km of embankment from Aricha to Zionpur 3. Other Guided accelerated siltation of charland Placement of buoys along the protected bank Infrastructure TRANCHE-3 1.RBP Around 5 km at Chauhali, Around 2 km at Zaffarganj Adaptation and maintenance 2. EMB offtake geometry for Dhaleswari offtake geometry for the GhiorKhal Around 23 km new embankment 3. Other Regulators, Fish passes Placement of buoys along the protected bank
Intended Benefits (+) and Known Potential Adverse Impacts (-) + Description Type - (impacted location, activity or asset; timing, extent or magnitude) ? Reduced flood + Whole area damage Reduced erosion + Whole bankline Navigation + More stable channel along protected bank with increased draught Land reclamation + 30 km² Water Management + Improved dry season flow in Dhaleswari for boro irrigation and cleaning the rivers around Dhaka Communication + Improved access in case a dedicated national highway standard road is built along the embankment from Dhaleswari to Aricha and beyond Land acquisition/loss - Associated with embankment – about 2 km² (40km*50m) floodplain land Resettlement - To be confirmed Fisheries ? Geotextile bag revetments provide shelter, attached chars potential spawning ground, protection from floating nets Improved river fish diversity due to dry season flow in distributaries and protection from floating nets (buoys)
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Supporting Studies River surveys by BWDB and the PPTA team Surveys Flood plain surveys along the Hurashagar and Kaijuri to Shariatpur Char-land Study Investigation of deposition rates of the char opposite of the Hurashagar/Baral outfall and upstream between Enayetpur and Jamuna Bridge River Flow Modeling 1-D HEC RAS modeling of flow patterns to determine the minimum width of a & Analytical Approach single channel river solution Flood Modeling Scenario 1: restoration of Hurashagar FCD embankment from Kaijuri to Benatia along the Jamuna, Benotia to Baghabari along the Hurashagar/Baral, and Baghabari to Shahjadpur along the Karatoa River Scenario 2: loss of flood protection in the Enayetpur area due to erosion and breach of the embankment EIA/SIA Environmental baseline and impacts of above works Resettlement 100% census and IOL, 20% SES for embankment and 2 km of riverbank protection
Version change log (latest first) Version created Change date Changes made + reasons for changes by change 10 May 2013 5.0 Updated for final report - ko 1 March 2013 4.0 Expanded description – ko 3 Oct 2012 2.0 Full description entered – ko 25 Sep 2012 1.0 Initial version of project description – slb
Page 41 PPTA 8054: BAN- Main River Flood and Bank Erosion Risk Management Program
Program Interventions Stabilizing the Jamuna Left Bank and Reducing Flooding: Tranche-1 to 3
Interventions are planned to progressively stabilize the Jamuna left bank from erosion. The stabilization starts from two highly erosion prone areas and develops with the requirements during the three tranches- During tranche-2 existing flood protection will be rehabilitated and during Tranche-3 extended to a consistent embankment line to the Dhaleswari River.
Tranche 1 to 3 12km riverbank protection
Tranche 2 12km embankment rehabilitation Aricha to Zionpur Tranche 3 23 km embankment constructionZionpur to Dhaleswari
Tranche 1-3 6km riverbank protection at Zafferganj
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Purpose: The purpose of the riverbank protection work is to start providing reliable protection that secures the bank at the two critical locations Chauhali and Zaffarganj. This protection is expected to develop over three tranches into long-reach protection guiding the river channel along the bank and at the downstream end away from the bank, in order to provide passive protection to the downstream area.
Existing flood protection from Aricha to Zionpur will be strengthened. The existing condition of this 12km long embankment is shown in the figure below. In tranche-3 the existing embankment will be extended by 23km in upstream direction to the Dhaleswari. It is expected that Dhaleswari and GhiorKhal, the two main distributaries in this area will get an offtake geometry that allows dry season inflow, while restricting the flood season inflow to return periods below 10 years in order to avoid heavy flooding but maintain a certain inflow of fertile fine sediments.
Page 43 PPTA 8054: BAN- Main River Flood and Bank Erosion Risk Management Program
The embankment crest level will be determined during tranche-1 based on the assessment of the 100- year flood water levels. A freeboard of 1.5 m applies throughout. The 2, 50, and 100-year flood water levels at Aricha are 9.5, 10.9 and 11.1m+PWD.
The estimated quantities for tranche-1 work are:
Structure Details Volume Comments Riverbank protection 1 km at Verakola geobags: Geotextile bag Chauhali: 1,760,000no 125kg revetments 250,000no 250kg Zafferganj: 690,000no 125kg 55,000no 250kg Concrete blocks: Chauhail: 54,000m³ Zafferganj: 21,000m³
For the purpose of flood modelling the adjacent areas JLB-2 and PLB-1 were considered together. 65% of the area (119,225 ha) are covered by JLB-1, while 66,895ha are covered by PLB-1). The total area of JLB-2 and PLB-1 can be broken down as follows:
Land Type Area (ha) Per Cent of Total (%) Gross Project Area 186,121 Adjusted Project Area protected by Embankment (APA) 135,552 100% Settlement Areas 32,836 24% Ponds, streams, other non-agricultural land 3,778 3% Net Cultivable Area (NCA) 98,908 73%
Most of the land is low lying and the area would be totally inundated during the 100-year water levels.
The flood modelling (Annex D) provides the following details for different flood characteristics. The 1998 flood is a high flood, the 2007 is moderate, and the 2003 is a low flood. The following table applies to the area of JLB-2:
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Areas (in ha) 1998 2003 2007 Adjusted project area (APA) 82,927 82,927 82,927 Settlement area 18,491 18,491 18,491 Other non-agricultural land 2,696 2,696 2,696 Net cultivable area (NCA) 61,740 61,740 61,740 F0 land (including flood free) 12,667 27,364 16,141 F1 land 171 855 954 F2 land 2,655 7,668 7,767 F3 land 36,279 24,669 33,750 F4 land 12,033 3,474 5,193 Total flooded cultivable area 51,174 36,783 47,844 Per cent of NCA flooded (%) 80% 57% 75% Per cent of APA flooded (%) 65% 48% 61%
The flood modelling demonstrates that the existing embankment line has a small benefit to the area, as it is largely open to the Jamuna flooding between Zionpur and Jamuna Bridge. As such alternative flood modelling scenarios were investigated out of which a lateral embankment along the Jamuna left bank was selected as it is the shortest embankment of the alternatives while providing most benefits (flood reduction). The following table shows the difference in flooding for the upgraded existing embankment (covering JLB-2 and PLB-1):
Area (ha) Existing situation Upgraded embankment Difference F0 land 1,992 5,345 +3,353 F1 land 11,295 11,673 +378 F2 land 40,261 39,987 -274 F3 land 67,397 64,512 -2,885 F4 land 5,550 4,977 -573
The new embankment line will reduce the flood damages in the area. After construction of the complete embankment in Tranche-3 the land type in JLB-2 would change as follows:
Change in area (ha) 1998 2003 2007 F0 land (including flood free) +18,621 +23,994 +27,711 F1 land +10,575 +5328 +6,813 F2 land +8739 -4347 -441 F3 land -29,187 -24,003 -32,031 F4 land -11,970 -3,465 -5,184 Change in total flooded NCA -16,902 -23,373 -26,766
For assessing economic benefits the 2007 flood was selected as representative moderate flood. Benefits were derived as follows:
(i) Selection of the inundated area (in ha) for with and without project scenario (refer to above tables)
F0 F1 F2 F3 F4 With project 43,852 7,767 7,326 1,719 9 Without project 16,141 954 7,767 33,750 5,193 Incremental 27,711 6,813 -441 -32,031 -5,184
(ii) Selection of area suitable for cropping (74.5%)
Page 45 PPTA 8054: BAN- Main River Flood and Bank Erosion Risk Management Program
F0 F1 F2 F3 F4 With project 32,648 5,783 5,454 1,280 7 Without project 12,017 710 5,783 25,127 3,866 Incremental 20,631 5,072 -328 -23,847 -3,860
(iii) Identification of crop intensity for different land types
F0 F1 F2 F3 F4 With project 226.1 200.0 200.0 200.0 0.0 Without project 226.1 195.1 198.2 199.0 100.0
(iv) Identify the total cultivated Area (ha)
F0 F1 F2 F3 F4 With project 73,818 11,565 10,909 2,560 0 Without project 27,171 1,386 11,461 50,006 3,866 Incremental 46,647 10,180 -553 -47,447 -3,866
(v) Identify the construction sequencing and the benefit development
Tranche 1 Tranche 2 Tranche 3 Total Length [km] 0 12 23 29 Phasing [%] 0 34.3 65.7 100.0
The land improvement for largely agriculturally based activities applies to the area suitable for cropping with special focus on flood mitigation and drainage but also irrigation (mostly maintaining sustainable irrigation infrastructure during times of flooding). To this end it is associated with the land types, which is more intensively agriculturally used after implementing the project. Improvements in flood mitigation are commonly associated with the reclassification of the type of land to the next higher class, or lifting it to a land type with less inundation. While this applies for all classes from F3 to F0, in this special case the more deeply flooded land types, F2 to F4, reduce for the with-project scenario. The total F0 and F1 land are is 51,600 ha with project as opposed to 17,100 ha without project, or a change of 34,500 ha. The figures for land suitable for cropping are 38,400 ha with project as opposed to 12,700 ha without project, translating into an increase of 25,700ha.
The improvement in land type translates into improvements in living conditions at household level. The average population density is 1340 persons per km² on the floodplain. Multiplying this figure with the total area of improved land types (F0 and F1 land) of 34,500 ha results in a flood risk reduction for 462,000 persons at the end of the program.
A 2.59 km wide strip of land eroded from 1973 until 2012 and a 0.12 km strip of land from 2007 until 2012. This translates into annual average erosion rates of 66 m over the whole period of 39 years and 24 m over the last five years of that period.
For estimating the economic feasibility the benefitted area erosion data have been estimated mimicking observed erosion patterns, which come and go periodically. To this end 5-year erosion patterns followed by 5-year without erosion are assumed. In order to estimate benefits, and in line with the program concept to prevent predicted erosion in key areas, the work is assumed to prevent erosion starting from its completion date. This means that works starting in Tranche-1 prevents erosion from year 4, works starting in Tranche-2 prevents erosion from year 7, and work starting in Tranche-3 prevents erosion from year 10. The assumed erosion rate for JRB-1 is 100 m per year, which reflects
Page 46 September 2013 A2 Sub-reach Descriptions local peak erosion rates corresponding roughly to the total average erosion rate over the last 5-years. As such 1 km of protection saves 10 ha of land annually from erosion or 50 ha over 5 years. This is the same after 10-years, assuming that the erosion rate stops during the second cycle. The following table summarizes the aggregate erosion losses in ha for each 5-year period of the project implementation.
location Length Annual Work 5- 10- 15- 20- 25- 30- [km] erosion [m] start years years years years years years Chauhali 5 100 year 1 100 250 350 500 600 750 Chauhali 3 100 year 4 - 120 150 270 300 420 Chauhali 5 100 year 7 - 50 250 300 500 550 Zaffarganj 2 100 year 1 40 100 140 200 240 300 Zaffarganj 2 100 year 4 - 80 100 180 200 280 Zaffarganj 2 100 year 7 - 40 100 120 200 220
Related to the physical work, there is land-acquisition and resettlement impact. The following figure shows the number of agricultural plot users, affected households and land requirements for different sections. It also indicates potential locations of construction camps.
Length (km) Land acquired (ha) Affected Households RBP 19 57 798 EMB 35 134.2 1802 Structures 2.46 0 Total 193.66 2600
Page 47 PPTA 8054: BAN- Main River Flood and Bank Erosion Risk Management Program
5 Padma Left Bank 1 – Paturia – Harirampur Priority Project Name ID Upazilas (Unions) Area River Area Population Padma Left Bank 1 PLB1 3 (35) 682 km² 23% 736,000
Bankline Total Erosion (1973- Flood extent Area Boro/Aman Population Density length 2009/2004-2009) (1998 / 2007) (total/floodplain) 25 km 3.35 km / 0.03 km 62% / 46% 18% / 34% 1080/1400
Situation The Padma starts as single channel after the confluence of Jamuna and Ganges. 10 km downstream of the confluence it bifurcates into two channels, carrying different percentages of its flow over time and enclosing an around 25 km long and up to 10 km wide char. Presently the southern channel is declining.
At the downstream boundary of this subproject reach, about 25 km downstream of the confluence, a more erosion resistant clay forms the northern (left) bank (marked in figure below). Upstream of this clay the Padma tends to erode substantial amounts of floodplains through outflanking channels, which periodically close (see following figure with bankline development). At this moment a historic, extreme meander loop is filled in and the river is flowing rather straight. The filled in area is around 30 km² (3000 ha) in size. The historic Dhaka Southwest Project embankment in this area is eroded and was not rebuild (also refer to JLB-2 maps from FAP 3). The char age map (1973-2009, Padma Bridge report) indicates that the anabranch between Harirampur and Faridpur is presently contracting in width with substantial areas along both banks recently silted in.
Figure from Padma Bridge design report
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Erosion at Harirampur
Figures from Padma Bridge design report
Future Scenarios Future channel planforms downstream of the bifurcation can consist of one or two channels. The initial morphological study for the upper Padma reach (Annex C, January 2013 PPTA report) indicates that the present two-channel system with one large char provides an overall acceptable solution and in terms of future river management (or stabilization) efforts the most pragmatic approach.
Page 49 PPTA 8054: BAN- Main River Flood and Bank Erosion Risk Management Program
It is expected that the Padma exhibits the currently straighter alignment along the north bank near Harirampur and continues building the recently deposited land to greater height. The field trip in December confirmed that roughly the upstream half has reached substantial height, while the downstream part is still low lying.
BWDB pursues some plans of the Nagarpur-Chauhali and the Jamuna-Padma left bank Project in this area going back to the FAP 3 recommendations (also refer to JLB-2). This project basically addresses the flooding issue in this area, providing drainage facilities and improved irrigation opportunities in addition.
Existing Works The Paturia ferry ghat is located at the upstream end of this sub reach. For dry season ferry operation a navigation channel is dredged regularly. Two LGED small scale projects are situated in this area.
Project Concept This area incorporates two BWDB priority projects: (i) riverbank protection along the left bank upstream of Harirampur to protect the large meander bend from forming again, and (ii) reconstruction of the Dhaka Southwest Project embankment from Paturia to Harirampur. The PPTA recognizes the opportunity of reclaiming around 3000 ha of lost flood plain land due to the present favorable morphological situation.
Tranche-1 • 7 km of riverbank protection at Harirampur covering the upstream of the old meander erosion, only geobag part • Pilot plantation of catkin for accelerated char growth Tranche-2 • 7 km of riverbank protection at Harirampur covering the upstream of the old meander erosion, only wave protection part • Reconstruction of the embankment from Paturia towards Mawa • Sluice gates for water management (including rehabilitation of existing sluice gates) Tranche-3 • About 5 km of riverbank protection in continuation of tranche-1 works • Sluice gates for water management (including rehabilitation of existing sluice gates)
Intervention Elements List by type Description (Location, dimensions or quantity) Infrastructure TRANCHE – 1 1.RBP Around 7 km with temporary wave protection 2. EMB none 3. Other Pilot plantation of catkin and monitoring of vertical char growth (up to floodplain level) 1. Buoys for navigation and fish protection along revetment work Infrastructure TRANCHE –2 1.RBP Around 7 km of permanent wave protection 2. EMB Around 17 km of rehabilitation with 8 km new embankment 3. Other Plantation of catkin for vertical char growth (up to floodplain level) Infrastructure TRANCHE – 3 1.RBP Around 5 km of riverbank protection 2. EMB None 3. Other Buoys for navigation and fish protection along revetment work
Page 50 September 2013 A2 Sub-reach Descriptions
Intended Benefits (+) and Known Potential Adverse Impacts (-) + Description Type - (impacted location, activity or asset; timing, extent or magnitude) ? Reduced flood + Whole area damage Reduced erosion + Whole bankline Navigation + More stable channel along protected bank with increased draught Land reclamation + Potential flood protected area around30km² Water Management + Improved conditions for dry season irrigation after reconstruction of embankment Communication + Improved access in case a dedicated national highway standard road is built along the embankment from Aricha to Dohar and beyond Land - Associated with embankment strengthening– about 1 km² (20km*50m – acquisition/loss assumption that existing land can be used) Resettlement - To be confirmed Fisheries ? Geotextile bag revetments provide shelter, attached chars potential spawning ground Improved river fish diversity due to protection from floating nets (buoys)
Version change log (latest first) Version created Change date Changes made + reasons for changes by change 30 May 2013 5.0 Updated for final report –ko 1 Mar 2013 4.0 Expanded description – ko 6 Feb2013 3.0 Finalization with more detailed work layouts – ko 25 Sep 2012 1.0 Initial version of project description – slb
Maps: Infrastructure Flood and erosion on satellite image Flood and erosion on DEM
Page 51 PPTA 8054: BAN- Main River Flood and Bank Erosion Risk Management Program
Program Interventions Stabilizing the Padma Left Bank, Recovering 3000ha of Lost Floodplain, and Reducing Flooding: Tranche-1 to 3
Interventions are planned to progressively stabilize the upper Padma left bank from erosion. The stabilization starts upstream of the highly erosion prone area periodically occupied by a meander loop and currently in a stage of accretion. Flood and riverbank protection develop during three tranches leading to progressive stabilization and comprehensive flood risk reduction from an upgraded flood embankment.
Tranche 3 5km riverbank protection
Tranche 2 25km embankment rehabilitation
Tranche 1 7km riverbank protection below water Tranche 2 7km riverbank protection above water
Page 52 September 2013 A2 Sub-reach Descriptions
Purpose: The purpose of the tranche-1 riverbank protection work is to provide under-water protection at the upstream end of the in-filled meander bend in order to secure around 3000 ha of newly accreted land from erosion. The upstream protection will be placed in Tranche-2, when the siltation process is expected to be further advanced. Downstream protection will be provided in Tranche-3.
Existing flood protection from Dohar to Paturia will be strengthened in tranche-2. The existing condition of this around25km long embankment is shown in the figure below
Page 53 PPTA 8054: BAN- Main River Flood and Bank Erosion Risk Management Program
The embankment crest level will be determined during tranche-1 based on the assessment of the 100- year flood water levels. A freeboard of 1.5 m applies throughout. The 2, 50, and 100-year flood water levels at Aricha are 9.5, 10.9 and 11.1 m+PWD.
The estimated quantities for tranche-1 work are: Structure Details Volume Comments Riverbank protection 7 km at Harirampur 125kg geobags: 1,500,000no Geotextile bag 250kg geobags: 1,200,000no revetments
For the purpose of flood modelling the adjacent areas JLB-2 and PLB-1 were considered together. 65% of the area (119,225ha) are covered by JLB-1, while 66,895ha are covered by PLB-1). The total area of JLB-2 and PLB-1 can be broken down as follows:
Land Type Area (ha) Per Cent of Total (%) Gross Project Area 186,121 Adjusted Project Area protected by Embankment (APA) 135,552 100% Settlement Areas 32,836 24% Ponds, streams, other non-agricultural land 3,778 3% Net Cultivable Area (NCA) 98,908 73%
Most of the land is low lying and the area would be totally inundated during the 100-year water levels.
The flood modelling (Annex D) provides the following details for different flood characteristics. The 1998 flood is a high flood, the 2007 is moderate, and the 2003 is a low flood. The following table applies to the area of PLB-1:
Areas (in ha) 1998 2003 2007 Adjusted project area (APA) 52,070 52,070 52,070 Settlement area 14,345 14,345 14,345 Other non-agricultural land 1082 1082 1082 Net cultivable area (NCA) 36,643 36,643 36,643 F0 land (including flood free) 12,646 21,718 14,194 F1 land 126 468 369 F2 land 3006 3411 4671 F3 land 13,509 10,863 15,156 F4 land 7884 1134 2565 Total flooded cultivable area 24,525 15,903 22,788 Per cent of NCA flooded (%) 66% 42% 62% Per cent of APA flooded (%) 49% 33% 46%
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The flood modelling demonstrates that the existing embankment line has a small benefit to the area, as it is largely open to the Jamuna flooding between Zionpur and Jamuna Bridge. As such alternative flood modelling scenarios were investigated out of which a lateral embankment along the Jamuna left bank was selected as it is the shortest embankment of the alternatives while providing most benefits (flood reduction). The following table shows the difference in flooding for the upgraded existing embankment (covering JLB-2 and PLB-1):
Area (ha) Existing situation Upgraded embankment Difference F0 land 1,992 5,345 +3,353 F1 land 11,295 11,673 +378 F2 land 40,261 39,987 -274 F3 land 67,397 64,512 -2,885 F4 land 5,550 4,977 -573
The new embankment line will reduce the flood damages in the area. After construction of the complete embankment at JLB-2 in Tranche-3 the land type in PLB-1 would change as follows:
Change in area (ha) 1998 2003 2007 F0 land (including flood free) +7416 +8280 +11,151 F1 land +4266 +2259 +3240 F2 land +2772 -693 -891 F3 land -8046 -9198 -11,781 F4 land -6732 -909 -2052 Change in total flooded NCA -5526 -7011 -9432
For assessing economic benefits the 2007 flood was selected as representative moderate flood. Benefits were derived as follows:
(i) Selection of the inundated area (in ha) for with and without project scenario (refer to above tables)
F0 F1 F2 F3 F4 With project 25,345 3,609 3,780 3,375 513 Without project 14,194 369 4,671 15,156 2,565 Incremental 11,151 3,240 -891 -11,781 -2,052
(ii) Selection of area suitable for cropping (70.4%)
F0 F1 F2 F3 F4 With project 17,836 2,540 2,660 2,375 361 Without project 9,989 260 3,287 10,666 1,805 Incremental 7,847 2,280 -627 -8,291 -1,444
(iii) Identification of crop intensity for different land types
F0 F1 F2 F3 F4 With project 267.4 200.0 200.0 198.3 0.0 Without project 267.4 178.3 188.4 198.3 100.0
(iv) Identify the total cultivated Area (ha)
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F0 F1 F2 F3 F4 With project 47,694 5,079 5,320 4,710 0 Without project 26,710 463 6,193 21,150 1,805 Incremental 20,984 4,616 -873 -16,440 -1,805
(v) Identify the construction sequencing and the benefit development
Tranche 1 Tranche 2 Tranche 3 Total Length [km] 0 17 0 29 Phasing [%] 100 0 100.0
The land improvement for largely agriculturally based activities applies to the area suitable for cropping with special focus on flood mitigation and drainage but also irrigation (mostly maintaining sustainable irrigation infrastructure during times of flooding). To this end it is associated with the land types, which is more intensively agriculturally used after implementing the project. Improvements in flood mitigation are commonly associated with the reclassification of the type of land to the next higher class, or lifting it to a land type with less inundation. While this applies for all classes from F3 to F0, in this special case the more deeply flooded land types, F2 to F4, reduce for the with-project scenario. The total F0 and F1 land are is 28,900 ha with project as opposed to 15,500 ha without project, or a change of 14,400 ha. The figures for land suitable for cropping are 20,400 ha with project as opposed to 10,300 ha without project, translating into an increase of 10,100ha.
The improvement in land type translates into improvements in living conditions at household level. The average population density is 1400 persons per km² on the floodplain. Multiplying this figure with the total area of improved land types (F0 and F1 land) of 14,400 ha results in a flood risk reduction for 202,000 persons at the end of the program.
A 3.35 km wide strip of land eroded from 1973 until 2009 and a 0.03 km strip of land from 2004 until 2009. This translates into annual average erosion rates of 93 m over the whole period of 34 years and 6 m over the last five years of that period.
For estimating the economic feasibility the benefitted area erosion data have been estimated mimicking observed erosion patterns, which come and go periodically. For this sub-reach there are two patterns that play a role: (i) The conventional approach of 5-year erosion patterns followed by 5-year without erosion: The assumed erosion rate for PLB-1 is 50 m per year, which reflects about half of the local peak erosion rates over the total period. (The average erosion rate over the last five years is not representative as it reflects a period of accretion, where the large meander bend downstream of Harirampur was silting in.) As such 1 km of protection saves 5 ha of land annually from erosion or 25 ha over 5 years. This is the same after 10-years, assuming that the erosion rate stops during the second cycle. (ii) The occupancy of a big meander bend along the bankline downstream of Harirampur: This bend is eroded progressively, assuming that the existing 12km long bankline erodes during the first year, followed by 11km during the second year and so on until the last km is eroded in year 12. Then the embayment will not eroded anymore and a cycle of fill will start. We assume that the erosion starts in year 6, during tranche-2.
In order to estimate benefits, and in line with the program concept to prevent predicted erosion in key areas, the work is assumed to prevent erosion starting from its completion date. This means that works starting in Tranche-1 prevents erosion from year 4, works starting in Tranche-2 prevents erosion from year 7, and work starting in Tranche-3 prevents erosion from year 10.
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The following table summarizes the aggregate erosion losses in ha for each 5-year period of the project implementation.
location Length Annual Work 5- 10- 15- 20- 25- 30- [km] erosion [m] start years years years years years years Harirampur 5 100 year 1 - 1500 2250 2340 2340 2340 Dohar 2 100 year 7 - 50 125 150 250 275
Related to the physical work, there is land-acquisition and resettlement impact. The following figure shows the number of agricultural plot users, affected households and land requirements for different sections. It also indicates potential locations of construction camps.
Length (km) Land acquired (ha) Affected Households RBP 12 36 504 EMB 48.1 48.1 2476 Structures 2.46 0 Total 86.56 2980
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6 Padma Left Bank 2 – Harirampur - Mawa Project Name ID Upazilas (Unions) Area River Area Population Padma Left Bank 2 PLB2 4 (50) 789 km² 12.3% 1,093,000
Bankline Total Erosion (1973- Flood extent Area Boro/Aman Population Density length 2009/2004-2009) (1998 / 2007) (total/floodplain) 30.4km 0.67 km / 0.06 km 53% / 44% 32% / 23% 1390/1580
Situation The Padma exhibits a distinct slowly developing switching pattern in this reach from meandering to straight, whereas the straight channel always follows the erosion resistant left bank. When returning from meandering to straight the river exhibits an anabranching planform for a short period of time. There is little riverbank erosion in this sub-reach even though the river can become very deep (more than 45 m), as a result of the erosion resistant clay layer. The Dhaka Southwest Project embankment is largely existing and functioning even though locally under erosion.
Future Scenarios Future channel planforms without work will likely continuing to switch with a periodicity of nearly 30 years. However, it is expected the construction of the Padma Bridge could lead to a more stabilized planform, as the south bank revetment would act as a second attractor of the channel. This could
Page 58 September 2013 A2 Sub-reach Descriptions extend the periods of meandering with a more stable char forming along the north bank. An initial “channelization” concept considers the long term stability of the meandering channel in this area, which means substantial land gains alongside the left bank.
Erosion in some locations endangers the existing Dhaka Southwest embankment. If the embankment is lost the area behind will be flooded at higher rate, substantially impacting on the living conditions.
Existing Works BWDB has provided some limited emergency work at two locations where the embankment is eroding (in 2012 at Dhulshura near Barrah Bazar).
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Six LGED small scale projects are situated in this area. The northern abutment for Padma Bridge is located at the downstream end of this area.
Project Concept Interventions in this area focus on providing ad-hoc stabilization to critically eroding reaches in order to protect the flood embankment from erosion. In later tranches provisional work on strengthening the existing Dhaka Southwest embankment including provision of a national highway standard road could be considered.
Tranche-1 • Limited emergency protection in critically eroding areas (2 km)
Tranche-2 • About 4 km of riverbank protection in continuation of tranche-1 works • Provisional: reconstruction of the embankment from Dohar to Mawa
Intervention Elements List by type Description (Location, dimensions or quantity) Infrastructure TRANCHE-1 provisional 1.RBP 2 km of emergency works (USD 500,000) Infrastructure TRANCHE-2 provisional 1.RBP 4 km in critically eroding reaches (USD 8.4M) 2. EMB Around 30 km of reconstruction and rehabilitation including road (provisional) 3. Other Sluice gates/regulators for water management
Intended Benefits (+) and Known Potential Adverse Impacts (-) + Description Type - (impacted location, activity or asset; timing, extent or magnitude) ? Reduced flood damage + Whole area Reduced erosion + Whole bankline Navigation Similar to present situation Land reclamation + Water Management + Improved conditions for flood season cropping after reconstruction of embankment Communication + Improved access in case a dedicated national highway standard road
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is built along the embankment from Dohar to Mawa and beyond Land acquisition/loss - Associated with embankment strengthening Resettlement - To be confirmed Fisheries ? Geotextile bag revetments provide shelter, attached chars potential spawning ground
Version change log (latest first) Version created Change date Changes made + reasons for changes by change 1 Mar 2013 4.0 Original concept – ko
Maps: Infrastructure Flood and erosion on satellite image Flood and erosion on DEM
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7 Padma Left Bank 3 – Mawa-Padma Outfall Project Name ID Upazilas (Unions) Area River Area Population Padma Left Bank 3 PLB3 3 (33) 440 km² 32.5% 740,000
Bankline Total Erosion (1973- Flood extent Area Boro/Aman Population Density length 2009/2004-2009) (1998 / 2007) (total/floodplain) 47.6 km 1.27 km / 0.08 km 22% / 12% 5% / 23% 1680/2490
Situation The Padma in this reach is characterized by the variable confluence morphology typically consisting of multiple channel joining the Meghna at different locations. There is no strong correlation with the upstream reaches. As a consequence of the variability erosion patterns vary widely over the confluence area (PLB-3, PRB-3, MLB-1,2, and MRB-1). At present the North Padma channel flowing along the sub-project reach is declining and exhibits a distinct meandering pattern.
Future Scenarios The future of the confluence depends on the influence of the river training works of Padma Bridge. A number of different scenarios were studied during the Padma Bridge design phase and superimposed with the past river corridor in this area. The non-invasive river training works will not cause dramatic downstream effects, as opposed to the dramatic changes entailed by Jamuna Bridge.
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The study of a number of options (example below) reveals that the only very limited erosion beyond the observed historic pattern is expected. This notwithstanding there remains substantial uncertainty as to when and where the channel will be located in future, not at last due to the uncertainty related to the construction start of the planned bridge.
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Existing Works BWDB has provided some riverbank protection in the Manikganj District There is no LGED small scale projects are situated in this area. The northern abutment for Padma Bridge is located at the upstream end of this area.
Project Concept Interventions in this area focus on providing ad-hoc stabilization to critically eroding reaches in order to protect the flood embankment from erosion. In later tranches provisional work on strengthening the existing Dhaka Southwest embankment including provision of a national highway standard road could be considered.
Tranche-1 • Limited emergency protection in critically eroding areas (1km)
Tranche-2 • About 4 km of riverbank protection in continuation of tranche-1 works • Provisional: reconstruction of the embankment from Dohar to Mawa
Intervention Elements List by type Description (Location, dimensions or quantity) Infrastructure TRANCHE-1 provisional 1.RBP 1 km of emergency works (USD 0.5 M) Infrastructure TRANCHE-2 provisional 1.RBP 4 km in critically eroding reaches (USD 8.4M) 2. EMB Around 30 km of reconstruction and rehabilitation including road (provisional) 3. Other Sluice gates/regulators for water management
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Intended Benefits (+) and Known Potential Adverse Impacts (-) + Description Type - (impacted location, activity or asset; timing, extent or magnitude) ? Reduced flood + Whole area damage Reduced erosion + Whole bankline Navigation Similar to present situation Land reclamation + Water Management + Improved conditions for flood season cropping after reconstruction of embankment Communication + Improved access in case a dedicated national highway standard road is built along the embankment from Dohar to Mawa and beyond Land acquisition/loss - Associated with embankment strengthening Resettlement - To be confirmed Fisheries ? Geotextile bag revetments provide shelter, attached chars potential spawning ground
Version change log (latest first) Version created Change date Changes made + reasons for changes by change 1 Mar 2013 4.0 Original concept – ko
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8 Padma Right Bank 1 – Ganges Barrage-Goalando Project Name ID Upazilas (Unions) Area River Area Population Padma Right Bank 1 PRB1 3 (38) 876 km² 14.8% 688,000
Bankline Total Erosion (1973- Flood extent Area Boro/Aman Population Density length 2009/2004-2009) (1998 / 2007) (total/floodplain) 55.4 km 1.39 km / 0.19 km 30% / 16% 11% / 41% 780/920
Situation The lower Ganges near the confluence with the Jamuna exhibits a distinct meandering pattern, which continues as deep, single channel in the confluence area. The area is less densely populated than the average of Bangladesh.
Future Scenarios Government plans to implement the Ganges Barrage in this area.
Existing Works BWDB has built several km of riverbank protection works at Rajbari. The work is ongoing in 2012/13 Fourteen LGED small scale projects are situated in this area.
Project Concept No interventions are planned in this area
Intervention Elements List by type Description (Location, dimensions or quantity) Infrastructure 1.RBP None 2. EMB None 3. Other None
Intended Benefits (+) and Known Potential Adverse Impacts (-) + Description Type - (impacted location, activity or asset; timing, extent or magnitude) ?
Version change log (latest first) Version created Change date Changes made + reasons for changes by change 1 Mar 2013 4.0 Initial version – ko
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9 Padma Right Bank 2 – Faridpur to Arial Khan Project Name ID Upazilas (Unions) Area River Area Population Padma Right Bank 1 PRB1 4 (38) 1055 km² 28.5% 978,000
Bankline Total Erosion (1973- Flood extent Area Boro/Aman Population Density length 2009/2004-2009) (1998 / 2007) (total/floodplain) 50.3 km 1.81 km / 0.12 km 38% / 30% 10% / 36% 930/1300
Situation The Padma starts as single channel after the confluence of Jamuna and Ganges. 10 km downstream of the confluence it bifurcates into two channels, carrying different percentages of its flow over time and enclosing an around 25 km long and up to 10 km wide char. Presently the southern channel is declining due to the occurrence of a cutoff (Refer to PLB-1). Due to this morphological development the town of Faridpur is not threatened by erosion any more. The situation was different in the early 2005, when bank erosion was still ongoing but a Netherlands expert team conducting a study predicted this future development. This notwithstanding BWDB built substantial length of riverbank protection to protect Chandpur.
The Padma Bridge design study identified that the area downstream of Faridpur contributes to substantial flood flows to the south through the Arial Khan, other small distributaries, and flow over the flood plain. This process continues to raise the floodplain level, a desirable effect countering the climate change induced sea level rise.
Future Scenarios Preferred future channel planforms downstream of the bifurcation can consist of one or two channels. The initial morphological study for the upper Padma reach (Annex C, January 2013 PPTA report) indicates that the present two-channel system with one large mid-channel char provides an overall acceptable solution and in terms of future river management (or stabilization) efforts the most pragmatic approach.
It is expected that the channel at Faridpur will decline further and north of Faridpur form a partial cut-off through the mid-channel char, which would allow recovering some of the lost floodplain land. The time frame for the formation of a major channel north of Faridpur is estimated to be about 5 years and subsequently this channel might start eroding the southern bank again.
Any future scenario building embankments has to consider large-scale impacts on the availability of fresh water and salinity figure from Shureswar project report intrusion in the southern area (left figure).
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Existing Works BWDB has built 10 km of riverbank protection works in the area of Faridpur from own funds. The work is currently continuing with 1.5 km under construction in 2012/13. In addition there is about 3.5 km of protection downstream of Faridpur at Decree Char, and 1km at Hajiganj Bazar. Five LGED small scale projects are situated in this area.
Project Concept There is no project planned in this area as there is substantial existing protection and no immediate erosion risk due to the continuing favorable morphological development.
Intervention Elements List by type Description (Location, dimensions or quantity) Infrastructure 1.RBP None 2. EMB None 3. Other None
Intended Benefits (+) and Known Potential Adverse Impacts (-) + Description Type - (impacted location, activity or asset; timing, extent or magnitude) ?
Version change log (latest first) Version created Change date Changes made + reasons for changes by change 10 May 2013 5.0 Updated for final report - ko 1 Mar 2013 4.0 Initial version – ko
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10 Padma Right Bank 3 – Arial Khan to Sariatpur Project Name ID Upazilas (Unions) Area River Area Population Padma Right Bank 3 PRB3 3 (47) 801 km² 30.3% 744,000
Bankline Tota Erosion (1973- Flood extent Area Boro/Aman Population Density length 2009/2004-2009) (1998 / 2007) (total/floodplain) 46.5 km 1.80 km / 0.18 km 42% / 37% 12% / 30% 930/1330
Situation The Padma exhibits a distinct slowly developing switching pattern in this reach from meandering to straight, whereas the straight channel always follows the erosion resistant left bank as explained in PLB-2.
Same as the PRB-2, this area contributes substantial flood season flow to the southern coastal area. To this extend the planned Padma Bridge approach road has more than 10% openings along its length to allow flood season water to pass.
Future Scenarios The overall river situation is explained in PLB-2 and characterized by the large river training work associated with the Padma Bridge.
In parallel BWDB is planning a new FCDI project in this area that is considered for future support by ADB (as extension of the South- West area development). This notwithstanding the FCDI project components between Arial Khan and Sureswar have been postponed (communication with CE Faridpur on 19 FEB 2013 during field trip.
figure from Sureswar report
Existing Works There is no existing work, however, the Bangladesh Bridge Authority has started construction of 2 km of riverbank protection downstream of the planned river training works in early 2013. Five LGED small scale projects are situated in this area.
Project Concept No interventions are planned in this area associated with the uncertainties related to the construction of the Padma Bridge river training works and the related future channel morphology.
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Intervention Elements List by type Description (Location, dimensions or quantity) Infrastructure 1.RBP None 2. EMB None 3. Other None
Intended Benefits (+) and Known Potential Adverse Impacts (-) + Description Type - (impacted location, activity or asset; timing, extent or magnitude) ?
Version change log (latest first) Version created Change date Changes made + reasons for changes by change 1 Mar 2013 4.0 Initial description – ko
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11 Meghna Right Bank 1 – Bhedarganj Project Name ID Upazilas (Unions) Area River Area Population Meghna Right Bank 1 MRB1 2 (21) 435 km² 23.9% 411,000
Bankline Total Erosion (1973- Flood extent Area Boro/Aman Population Density length 2009/2004-2009) (1998 / 2007) (total/floodplain) 34.1 km 1.85 km / 0.26 km 27% / 15% 35% / 40% 950/1240
Situation The variable confluence geometry governing erosion and accretion patterns has been described in PLB- 3.
The higher area of the Sureswar block, clearly visible on the satellite image, consists of old marine clay and is classified as very erosion resistant. It also blocks the flow to the east, as demonstrated by channels upstream (NariaKhal) and downstream of the block.
Currently out of 30 km of riverbanks (extending beyond the Chandpur boundary along the Sureswar FCDI banks) 7 km are eroding at two locations of the south Padma channel and 5km in one location along the Lower Meghna right bank.
figure from Sureswar report
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Future Scenarios The overall river situation is explained in PLB-3 and characterized by the variability of the confluence geometry. This will be somewhat affected by the large river training work associated with the Padma Bridge. Depending on the future channel planform, there is substantial potential for additional large accretion in this area, if the Padma is guided as single meandering channel from the bridge to Chandpur.
BWDB is planning a new FCDI project (see PRB-3) in this area that is considered for future support by ADB, specifically Unit 3 and 4 (as extension of the South-West area development). If these Units are selected for a new future FCDI program financed by ADB, this MRP is supposed to protect eroding river banks up to the level of Chandpur.
Existing Works BWDB is implementing riverbank protection along the town of Sureswar in 2013 Three LGED small scale projects are situated in this area.
Project Concept Interventions in this area are contingent to future ADB involvement in a new FCDI project. Only riverbank protection will be considered from this program, at this moment estimated around 10km. The feasibility will be driven by the FCDI project, including the cost for additional riverbank protection. In order to reap potential benefits from future accretion, and to design riverbank protection for the environment of one of the largest confluences in the world, substantial supporting studies will be required in Tranche-1 or 2.
Intervention Elements List by type Description (Location, dimensions or quantity) Infrastructure TRANCHE-2 or 3 1.RBP Potentially up to 10km 2. EMB None 3. Other None
Intended Benefits (+) and Known Potential Adverse Impacts (-) + Description Type - (impacted location, activity or asset; timing, extent or magnitude) ? Reduced erosion + Whole bankline other + With ADB supported FCDI project
Version change log (latest first) Version created Change date Changes made + reasons for changes by change 1 Mar 2013 4.0 Initial description – ko
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12 Meghna Left Bank 1 – MDIP Project Name ID Upazilas (Unions) Area River Area Population Meghna left Bank 1 MLB1 1 (14) 278 km² 27.8% 292,000
Bankline Total Erosion (1973- Flood extent Area Boro/Aman Population Density length 2009/2004-2009) (1998 / 2007) (total/floodplain) 21.4 km 0.94 km / 0.05 km 37% / 7% 63% / 47% 1050/1460
Situation The project area is the Meghna - Dhonagoda Irrigation Project, support by ADB during a CAD project from 1995 -2003 and subsequently protected from erosion through JMREMP from 2004 to 2011. The erosion protection involves 4.5 km at Ekhlaspur and 7 km along different reaches of the meandering Dhonagoda river.
The area is low lying and experience annual flooding of up to six months prior to construction of the ring embankment. During the early 1990s and early 2000s the North Padma channel was dominant which created a large erosion pressure at Eklaspur. This channel is declined and the critical bank has been protected. The figure is from JMREMP, 2005
Future Scenarios The overall river situation is explained in PLB-3 and characterized by the variability of the confluence geometry and the large river training work associated with the Padma Bridge.It is not expected that major riverbank erosion will happen in this area. However, the existing embankment remain vulnerable to seepage (“boiling”) failure specifically during higher floods.
Existing Works 4.5 km of riverbank protection built under JMREMP, including strengthening of the Ekhlaspur hard point. There is no LGED small scale project in this area.
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Project Concept Provisional interventions relate to the strengthening of the embankment by reducing the seepage risk during higher floods. The protected riverbank would provide shelter for fish, however is systematically overfished from floating nets. To this end it is suggested to place three navigation buoys to reduce the impact of floating nets and enhance the fish stock.
Intervention Elements List by type Description (Location, dimensions or quantity) Infrastructure TRANCHE-2 or 3 1.RBP None 2. EMB Grouting or other measures to reduce seepage 3. Other Buoys for navigation and reduction of overfishing from floating nets
Intended Benefits (+) and Known Potential Adverse Impacts (-) + Description Type - (impacted location, activity or asset; timing, extent or magnitude) ? Reduced flood damage + Whole area Reduced erosion + existing Navigation Improvement through buoys Land reclamation + Water Management + existing Communication + existing Land acquisition/loss - None Resettlement - None (temporary relocation of squatters in areas where embankment grouting would be conducted – for few weeks might become necessary) Fisheries ? Geotextile bag revetments provide shelter, attached chars potential spawning ground Buoys reduce the overfishing
Version change log (latest first) Version created Change date Changes made + reasons for changes by change 1 Mar 2013 4.0 Initial description – ko
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13 Meghna Left Bank 2 – Matlab to Chandpur Project Name ID Upazilas (Unions) Area River Area Population Meghna left Bank 2 MLB2 2 (22) 440 km² 36.5% 676,000
Bankline Total Erosion (1973- Flood extent Area Boro/Aman Population Density length 2009/2004-2009) (1998 / 2007) (total/floodplain) 24.4 km 0.54 km / 0.11 km 23% / 17% 47% / 25% 1530/2420
Situation The project area constitutes the eastern boundary of the Padma-Meghna confluence. As the confluence shows a consistent tendency to move to the east, the Chandpur Town protection arrests this movement and as such is fundamental for the stability of the whole Lower Meghna, starting with the Chandpur Irrigation Project. While at this moment little erosion happens, due to the somewhat favorable (for Chandpur) confluence geometry, long term morphological developments will change this. The present scour level is around 50 m. The steep underwater slopes entail a high risk of instability.
NA MEGH ER
LOW 0 C -5 ro ss Se -10 ctio n NATUN BAZAR -15 -20
-25 MOLE HEAD Slump 2001 -30
Filled -35
-40
-45 Da -50 ka -55 ti a Ri -60 v er -65 PURAN BAZAR
0 100 200 300 400 0 Chandpur Scour Depth -20
-40
-60
-80 1960 1980 2000 2020
Future Scenarios The overall river situation is explained in PLB-3 and characterized by the variability of the confluence geometry and the large river training work associated with the Padma Bridge. The stability of Chandpur remains a concern for the stability of the whole downstream estuary.
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Existing Works 0.8 km of riverbank protection protects the “mole head” from erosion. The work has been built in phases since the 1960s building on earlier work during the British period and periodically upgraded. There is one LGED small scale project in this area.
Project Concept Provisional interventions relate to the strengthening of Chandpur Town Protection after thorough study of the confluence geometry and future expected changes due to Padma Bridge and climate change impacts.
The project concept can build on earlier work implemented after the 1988 flood and studied in the FAP 9.1 Meghna Short Term Study report in the early 1990s. The use of modern technologies will allow optimizing the designs. A fundamental is providing a wide stable apron at present river levels and then to build up the slope to flatter angles. Suitable technologies are the dumping of large sand-filled containers of different dimensions during the dry season from bottom dump barges.
Intervention Elements List by type Description (Location, dimensions or quantity) Infrastructure TRANCHE-2 or 3 1.RBP Town protection, around 2 km 2. EMB 3. Other
Intended Benefits (+) and Known Potential Adverse Impacts (-) + Description Type - (impacted location, activity or asset; timing, extent or magnitude) ? Reduced flood damage + none Reduced erosion + Lower Meghna estuary Navigation Improvement through reduced turbulence Land acquisition/loss - None Resettlement - None as underwater works Fisheries ? Geotextile bag revetments provide shelter,
Version change log (latest first) Version created Change date Changes made + reasons for changes by change 1 Mar 2013 4.0 Initial description – ko
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