Project: Natural Drainage Solutions for Khulna City

Team lead, Euroconsult Mott MacDonald BV (EMM), has worked extensively in the coastal region of Bangladesh since the 1970s in rural and urban infrastructure development, river engineering, irrigation and drainage, water supply and wastewater, health and education, municipal capacity building, power and transportation. From 2014, EMM supported the preparation and, from October 2018, the implementation of the Bangladesh Delta Plan 2100. EMM’s projects are supported from its Bangladesh branch office. As part of the Mott MacDonald Group, EMM can also draw upon the global experience, networks and resources of its staff in 150 countries.

KUET-URP supports the project in the area of urban design and planning and contributes its detailed knowledge of Khulna’s institutions and urban issues. During the first phase of the project, KUET’s on-campus Design Studio enabled students and academic staff to engage and contribute solutions.

Nearly one third of the land in the city of Khulna is currently flood prone.

This may increase to half by 2050 if climate change leads to more erratic rainfall and sea level rise as projected. These threats are exacerbated by the city's defective drainage system and frequent clogging of drains by solid waste. As a result, floodwaters often cause prolonged waterlogging in parts of the city, which interrupts daily life and causes health and safety concerns.

Natural Drainage Solutions for Khulna City seeks to recover the functionality of Khulna's water system by improving solid waste collection and upgrading the drainage infrastructure in the city. The team's proposal promotes collection and reuse of solid waste through a simple, decentralized sewage system, and highlights the vital importance of strong input and involvement from local communities. Investments are also recommended to safeguard ponds, create additional reservoirs, and rehabilitate canals, drains, and the Mayur River.

During the first five-year phase of the project, further studies and discussions with stakeholders will enable optimal solutions to be developed for storage of storm water in Khulna's waterbodies. Ultimately, decision makers will consider future water requirements under climate change conditions, availability of suitable storage locations, land prices, and whether limited pumping and land raising can be done in strategic locations. The plan uses an adaptive delta management approach, by scaling up existing good practices, integrating with planned projects, and improving the coordination and dialogue between the municipal services sectors, community partners, and other institutions.

The team's first proposal reduces flooding and waterlogging in Khulna while maximizing storage of storm water runoff.

The whole catchment basin of the Mayur River, including peri-urban and rural areas in adjacent polders, is considered in design. Khulna's many ponds are gradually connected to the city’s drainage system to store surface water immediately after storm events and delay runoff to adjacent khals and to the river itself.

In the short term, between 2020-2025, the team's proposal implements the following measures for drainage improvement:

• Rehabilitation and improvement of the existing drainage network, including the rehabilitation and improvement of khals and drains which are directly connected to the Mayur River;
• Repairing the Alutola sluice structure;
• Rehabilitation and reconstruction of cross culverts and 15 outfall structures on the Mayur River;
• Elevated embankments on both side of the Mayur River and low-cost pumps at the end of each outfall so that water drains properly to the river;
• Removal of hyacinths and solid waste from the Mayur River to restore its natural flow;
• The construction of two new bridges on the Mayur River for pedestrian and and light vehicle traffic; and
• Further studies to improve the drain connectivity inside the catchment area so that runoff water is drained properly and effectively.

Over the past decade, water storage capacity in Khulna has been greatly reduced as a result of pond filling and urbanization.

Capturing stormwater runoff will become increasingly important in the next 15 years. The supply of the new Madhumati surface water pipeline will face peak demand in 2035, and extraction from the deeper aquifer has already reached sustainable limits. At present there is insufficient support amongs stakeholders for creating additional reservoir capacity, although the team has identified a few potential sites for this in the peri-urban area.

The team's proposal focuses on safeguarding existing ponds and enhancing their storage capacity, water quality, and value to owners and users. Requiring new or enhanced ponds as part of new real estate developments in KCC’s extended area should be enacted into policy. The potential to create larger reservoirs in peri-urban areas to the west and southwest of the city could explored at a later date, when more information becomes available about Khulna's growth trajectory and likely developments regarding the hydrology of the greater Khulna region.

Three different development packages were created for different categories of existing urban ponds based on their ownership. For each pond type there will be a different main objective along with several co-benefits, including: providing space for recreation; increasing domestic water supply; benefitting household incomes; avoiding land fill, and creating resources. Different partnership types were developed and champions selected for the various types of ponds.

The key goal of the team's third proposal for sanitation and solid waste management is to ensure maximum benefit and long-term sustainability of drainage interventions.

In addition to contributing to reduced flooding and waterlogging, improved sanitation and solid waste management will result in improved public health and local environmental quality. The general principle will be to scale up existing good practices and improve coordination and dialogue between relevant institutions. Drainage improvements will be conditional on a simultaneous committment to improving the sanitation and solid waste situation per neighborhood. This therefore requires sufficient communication with, and support from, the local community.

One of the biggest challenges the centralised sewage system will face is developing the tertiary network of household connections and the subsequent collection of tariffs. This relies on a significant amount of advocacy work, particularly as many customers are used to discharging their waste for free. The team's interventions in the sanitation system improve the sewage management systems over the immediate- to medium-term while being cognisant of longer-term integration with the central sewerage system. Therefore, redundant or wasted investments in infrastructure are avoided.