Guwahati is set to begin work on a comprehensive drainage master plan to address chronic flooding issues, following a recent tragedy highlighting the city's drainage problems
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Guwahati is set to begin work on the long-awaited drainage master plan aimed at addressing the city's chronic flooding issues. The urgency of the project has been underscored by a recent tragedy that claimed the life of an eight-year-old boy, Avinash Sarkar, who was swept away by floodwaters after falling into an open drain in Jyotinagar on July 4. Despite desperate attempts by his father to save him, Avinash was carried away by the fast-moving water. His body was found three days later, sparking public outrage and criticism of the city's drainage system.
However, the Guwahati Metropolitan Development Authority (GMDA) is moving forward with a comprehensive drainage master plan.
Talking to GPlus, a senior GMDA official said that the work will commence within 15 days. "The government has approved the preparation of the Guwahati Drainage Master Plan, with a budget of approximately ₹12 crore," he said.
The GMDA has enlisted Royal HaskoningDHV, a consultancy firm, to prepare the plan. The project will involve a multi-stage exercise in collaboration with various stakeholders, including the Urban Local Body (ULB), Water Resource Department, Public Works Department (PWD), and others. The project is divided into two stages:
Stage I: Master Plans
In this stage, the consultant will prepare master plans for Guwahati to identify the existing conditions of flooding, using a scientific approach that includes hydraulic modeling. This will revalidate the drainage master plan prepared in 2008, taking into account projected climate change impacts and the city's development plan.
Stage II: Detailed Project Reports (DPRs)
The second stage involves the preparation of DPRs for development options based on technical, economic, and financial viability, and environmental and social safeguard considerations. The DPRs will focus on storm water management for Guwahati.
Throughout the project, the consultant will maintain records of all discussions, meetings, and presentations, ensuring thorough documentation of the process.
The earlier storm water drainage report for Guwahati was prepared in 2008 by M/s Tahal Consulting Engineers Ltd. However, no major construction work was undertaken, and the city continues to suffer from several issues:
• Many storm water drains are not connected to final outfalls.
• The vertical profile of existing drains often lacks a falling gradient, leading to stagnation, silt deposition, and reduced carrying capacity.
• Large quantities of silt ingress from hill catchments due to denudation.
• Inadequate inlet sizes of existing drains.
• Illegal encroachment over storm water drains.
• Disposal of sewage and garbage in the drains.
• Inadequate sizes of some drains.
Zoning for Drainage System
The geographical area of Guwahati is approximately 320 sq km. The Master Plan for the Guwahati Metropolitan Area 2025 divides the project boundary into two parts: North Guwahati and South Guwahati. Based on topographical features, the area is divided into six drainage basins that ultimately drain into the Brahmaputra River either directly or through various channels and water bodies. These basins are:
• Silsako Basin: Covers 5,272 hectares in the east of Guwahati, including military areas, refineries, and industrial townships. The area slopes towards Silsako Beel, which connects to the Brahmaputra River via Bondajan River.
• Bharalu Basin: The most flood-prone basin with a catchment area of 4,886 hectares, including hills and parts of Meghalaya. Encroaching developments have blocked natural drainage patterns, causing severe flooding during heavy rains.
• Dipor Basin: The largest drainage basin in Guwahati, covering 8,632 hectares. River Basistha discharges into Deepor Beel. The design flood for the catchment of River Basistha is approximately 274 cubic meters per second (cumecs).
• Foreshore Basin: Includes main residential, commercial, institutional, and business areas in Guwahati. Only short-duration waterlogging occurs in some areas.
• Kalmoni Basin: Falls outside the Guwahati Metropolitan area, covering 6,650 hectares. The major outlet, River Kalmoni, drains into the Brahmaputra through Deepor Beel and other channels.
• Kalmoni Basin: Falls outside the Guwahati Metropolitan area, covering 6,650 hectares. The major outlet, River Kalmoni, drains into the Brahmaputra through Deepor Beel and other channels.
• North Guwahati Basin: Comprises hill ranges to the north and west, covering 2,780 hectares. The area drains into the Brahmaputra either directly or via Numali Jalah Beel.
Consultant Tasks
The consultant, Royal HaskoningDHV, will carry out several tasks, including:
• Mobilisation: The team leader will set up the project office and mobilise key team members, equipment, and peripherals.
• Submission of Inception Report: The consultant will review all available reports and data, identify gaps, and present an action plan for data collection. A draft Inception Report will be prepared and finalised in discussion with the Executing Agency (EA).
• Situational Analysis & Data Collection: Topographical surveys and investigations will be conducted to develop GIS base maps, assess drainage conditions, wastewater quality, historical flooding data, and hydrometeorology. The consultant will also review climate change projections and existing drainage structures, and collect socioeconomic and physical data.
• Preparation and Presentation of Draft Master Plans: The draft master plan will address existing conveyance and disposal systems for wastewater and surface runoff, the topography and development patterns of the project area, and ththe integration of climate change adaptation measures.
The consultant will use innovative approaches, including remote sensing satellite data, for hydraulic analysis and will maintain comprehensive records of all project-related activities.
While the initiation of the Guwahati Drainage Master Plan is a welcome step, it raises questions about why it took such a devastating incident to spur action. The plan, with its ₹12 crore budget and involvement of multiple agencies, promises to address the city's chronic flooding and drainage problems. However, the real test will be in its execution and the timely implementation of proposed solutions.
