Student Advising

M. Shah Alam Khan

Name of the student: MD. SHARIF IMAM IB-N-E AMIR

Program :  M. Sc. (WRD)

Title: SOCIO-TECHNICAL ASSESSMENT OF SEDIMENT MANAGEMENT OPTIONS IN TIDAL BASINS IN SOUTHWESTERN BANGLADESH

Background and present state of the problem:

The rivers of the southwestern region in Bangladesh are characterized by active deposition of sediment causing significant reduction in their drainage capacity. Besides, construction of costal polders that de-linked the floodplains from the rivers, and diminished upstream flow during the dry season deteriorated the sedimentation problem in this region (IWM, 2007). Consequently, this area has been experiencing severe drainage congestion and water logging since the early eighties. To solve these long-standing problems, the Khulna-Jessore Drainage Rehabilitation Project (KJDRP) was implemented during 1994-2002 (IWM, 2007). Later on, a popular concept based on generations of indigenous water management practices, formally known as Tidal River Management (TRM), was adopted. TRM would allow natural movement of sediment-borne tidal water into a beel (tidal basin) and allow deposition of sediment in the beel. During low tide the outgoing water would erode the river bed and increase the drainage capacity. After implementation of the project the prevailing drainage congestion was partially solved and agricultural, social and economic benefits were achieved (SMEC, 2002).

However, major problems in the area include non-uniform sedimentation inside the beel and inefficient performance of the flow control interventions, institutional conflicts among government agencies, water management associations (WMAs), NGOs and local government institutions (LGIs) regarding TRM, and social conflicts among various groups including farmers, fishermen and landowners resulting from shrimp farming and loss of indigenous varieties of fish and crop bio-diversity. Though, shrimp cultivation was gaining hold in the project area and had generated extra income but these shrimp ghers may give rise to drainage congestion (CEGIS, 2002)

However, the TRM was not implemented in accordance with people's suggestions. The failed project has now left a legacy of environmental disaster exemplified by silted-up, dead rivers, permanent inundation of thousands of hectares of land and the loss of indigenous varieties of fish and crop bio-diversity. The embankments disconnected the rivers from floodplain/wetlands, cutting fish migration routes and disturbing the spawning areas of indigenous fish varieties. A number of local fish varieties have almost become extinct. Although the summary environmental impact assessment clearly anticipated that the project would disrupt the spawning areas of indigenous fish, steps were not taken to address the issue. Moreover, the land acquired for the TRM was not compensated. Local wisdom and water management practices were undermined.

Sediment management and river morphology are the most difficult and demanding technical aspect of the study area (SMEC, 2002). People give their land for tidal basin without compensation wishing that the land will rise after three or four years. However, monitoring results and community consultation reveal that the sedimentation inside the tidal basins is very poor. This is done due to maintain proper sediment management inside the tidal basin. Therefore, sediment management is the most important criteria for the successful TRM practice in future.

Objectives with specific aims and possible outcome:

(i)   To determine and analyze all relevant natural, technical, social and institutional causes behind problems with sediment management; and

(ii)  Application of sediment transport model of the study area which will help to analyze different socially acceptable and technically feasible options for uniform sediment deposition inside the tidal basin

Possible Outcome: This study is important for the effective TRM practices and expected to provide a numerical model for design and situation analysis.

Outline of the Methodology:

Two suitable beels in the Bhabodah area will be selected for this study, one at the upstream and another at the downstream of the Hari river. One beel will be selected where TRM has been operationalized and another where it is under process. A two dimensional cohesive sediment transport model will be developed integrating the tidal basin and rivers using the MIKE21 FM modelling system (DHI water and environment, 2007). This numerical model will used to analyze various options including multiple cut for the proper sediment management inside the tidal basin. The downstream model boundary will be defined by the observed time series sediment concentration, and the upstream boundary will be a closed boundary since upstream influx sediment will not enter into the river during dry season. The model will be calibrated against observed sediment concentration covering neap and spring tides.

Appropriate field research techniques and tools will be applied to understand the views and opinions of the key stakeholders regarding sediment management and successful TRM operation. Based on these analyses several options for sediment management in the tidal basin will developed and analyze using the sediment transport model to assess the technical feasibility of these options.

References:

IWM (2009), Mathematical Modelling Study for Planning and Design of Beel Kapalia Tidal Basin, Final Report, Bangladesh Water Development Board.

DHI Water and Environment (2007), MIKE 21 FLOW MODULE (User Guide; Mud Transport Module), Danish Hydraulic Institute.

Choudhury, S.U., Khan, Z.H. (2007), Case studies for Sustainable Drainage Improvement under Tidal River Management in Khulna Jessore area, International Conference on Water & Flood Management (ICWFM-2007), 12-14 March 2007, Dhaka, Bangladesh.

IWM (2007), Monitoring the Effects of Beel Khuksia TRM Basin and Dredging of Hari River for Drainage Improvement of Bhabodah Area, Final Report, Bangladesh Water Development Board.

IWM (2006), Monitoring the Performance of Beel Kedaria TRM and Baseline Study for Beel Khuksia, Final Report, Bangladesh Water Development Board.

IWM (2005), Monitoring of Hydrological and Hydraulic Parameters on Tidal River Management under KJDRP Area, Final Report, Bangladesh Water Development Board.

SMEC (2002), Khulna Jessore Drainage Rehabilitation Project, Project Completion Report (Final), Bangladesh Water Development Board.

CEGIS (2002), Monitoring and Integration of the Environmental and Socio-economic impacts of implementing the Tidal River Management options to solve the problem of drainage congestion in KJDRP area, Final Report (Part A, Monitoring), Bangladesh Water Development Board.

SMEC (2002), Khulna-Jessore Drainage Rehabilitation Project, Project Completion Report (Final), Bangladesh Water Development Board.

EGIS (1998), Environmental Impact Assessment and Social Impact Assessment of Khulna-Jessore Drainage Rehabilitation Project, Final Report, Water Resources Planning Organization

SMEC (1997), Khulna-Jessore Drainage Rehabilitation Project, Feasibility Study Report for Overall Drainage Plan, Bangladesh Water Development Board.

SMEC (1997), Khulna-Jessore Drainage Rehabilitation Project, Sediment and River Morphology Study, Bangladesh Water Development Board.

Halcrow and Partners (1993), Southwest Area Water Resources Management Project, Final Report (Volume 4, Coastal Studies), Flood Plan Coordination Organization.

Haskoning and Associates (1993), Second Coastal Embankment Rehabilitation Project, Volume I: Executive Summary and Main Report, Bangladesh water Development Board.

O' Brien, M.P., (1969), Equilibrium Flow Areas of Inlets on Sandy Coast, Journal of the Water Ways and Harbours, DIV, Proc.A.S.C.E.

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