Strategic shift in Guwahati’s flood mitigation

Diversion of stormwater runoff from Meghalaya hills to Deepor Beel and Silsako Beel is pivotal to mitigating the worsening artificial flooding in Guwahati city and the Jorabat area. The approval by the Asian Development Bank for the Rs 183 crore project submitted by the Assam government for diversion of water from Meghalaya hills along the Bahini river catchment marks a strategic shift from patchwork fixes to a long-term solution. Strategic and long-term solutions in the other five drainage basins of the city – Bharalu, Mora Bharalu, Hathinala, Deepor Beel and Basistha basins – are crucial for comprehensive urban flood risk mitigation in the capital city. Nevertheless, the ADB’s approval of the Bahini basin project brightens hope for removing the financial bottleneck stalling long-term flood risk mitigation plans for the entire city. The project seeks to increase the discharging capacity of the existing Bahini River channel; create a diversion channel along the highway roadside drain; and constructa sponge pond to absorb stormwater in a low-lying area within the campus of Assam Power Distribution Corporation Limited at Six Mile. Encroachment of natural drainage channels of Bahini and other river and wetland basins due to unplanned and rapid urbanisation has drastically reduced their stormwater discharge capacities. Massive deforestation in hills in Meghalaya and Guwahati and ecological degradation of the watersheds have led to an increase in siltation and debris load in the drainage channel, making the current band-aid response, such as desilting the drains and wetlands, ineffective in flood risk mitigation. The intensity of flooding in the city has increased, with more areas continuing to reel under prolonged waterlogging during rainy days. Crores of public funds spent in sporadic desilting exercises ahead of the monsoon literally go down the drain with no visible mitigation and no respite for people in chronically affected localities. As the Bahini River originates in the Meghalaya hills and flows into Guwahati for a stretch of 8.21 km with its basin spanning a vast area of 17 sq. km, the project restoring the natural drainage in the entire basin is crucial for achieving the key goals. The proposed sponge pond to be constructed on the bank of the Bahini River will have a storage capacity of 60,000 cubic metres that is projected to mitigate peak inflows of 33 cubic metres per second, but timely execution of desilting of the proposed pond will be critical to achieving the targeted mitigation goals. Increasing the width of the existing stormwater drain along NH27 for diversion of water from Meghalaya hills from the present width in the range of 1.5 metres to 2.2 metres to 4 metres will be proven effective only when the problem of siltation and garbage disposal in the drain are also effectively addressed. Restoration of the degraded landscape in the upper catchment of the Bahini River in the Meghalaya hills and putting in place a scientific solid waste management system will be necessary and will require the full cooperation of the Meghalaya government. If the problem of siltation on account of unchecked destruction of the hill ecology and garbage disposal in the river remains unaddressed, then the discharge capacity of the Bahini channel will continue to be suboptimal even after implementation of all the components of the project, and the engineered interventions will fail to provide a sustainable solution. The project planning outlines a critical gap in the drainage system in the Bahini basin, with about 4.26 km of drains found to be lacking the correct gradient for optimal flow, and corrects the gradient to enhance flow capacity and prevent prolonged waterlogging in the Rukminigaon area during peak monsoon days. Overcoming institutional bottlenecks such as chronic delays, bureaucratic apathy and piecemeal execution and poor planning is essential to ensure that the past track record of poor performance in the execution of externally aided projects in the city is not repeated in the execution of the Bahini basin project. Lack of proper coordination among different agencies engaged in infrastructure development and public utility project implementation, observed in some of the ongoing projects, if left unaddressed, can adversely affect ADB-aided project execution for flood risk mitigation in the city. Such harsh realities call for empowering the Project Management Unit (PMU), to be established within the Assam Urban Infrastructure Development and Finance Corporation Limited, which will be responsible for management, coordination and execution of all activities funded under this project, with a robust monitoring and oversight mechanism to keep track of progress and quality control of work in real time. Drastic change in rainfall pattern due to climate change impact demands that all components of the Bahini basin project are climate-resilient and ecologically sound so that intended outcomes are not compromised by design flaws. Optimal utilisation of the seasonal window of non-rainy days will be crucial for expeditious implementation and prevent delay on account of monsoon-triggered disruption. Transparency in fund utilisation will be critical to uphold public trust in externally aided infrastructure projects.