Flooding is one of the most frequent and devastating natural disasters worldwide, affecting millions of people annually and causing severe economic losses. In monsoon-prone regions such as the Brahmaputra River catchment, extreme rainfall events, tributary networks, and river morphology exacerbate flood risks. Nature-based solutions (NbS), such as wetland restoration and management, offer a sustainable alternative to conventional flood mitigation strategies.
How do wetlands reduce flooding
This study, based on the research paper "Assessing the Efficacy of Hydro-Ecological Based Wetland Management Approach for Flood Resilience of a Large River Catchment" by Rishi Gupta et al. evaluates a hydro-ecological based wetland management approach, examining its efficacy in flood risk reduction and proposing recommendations for sustainable wetland rejuvenation and management.
Key findings
Efficacy of wetland rejuvenation in flood mitigation
The study highlights that rejuvenation of wetlands plays a significant role in reducing flood risks by increasing water retention and controlled release. Existing wetlands contribute to peak streamflow reduction by approximately 1-2% at the catchment outlet, while rejuvenated wetlands can achieve up to 8% reduction.
On a tributary scale, the improvements are even more pronounced, with streamflow reductions reaching nearly 30% in some cases. Furthermore, the occurrence of flood threat level events at key cities within the catchment area was significantly reduced by up to 60% due to wetland rejuvenation, thereby reducing the socio-economic impacts of floods.
Impact of wetland location on streamflow reduction
The study also demonstrates that the location of wetlands plays a crucial role in determining their effectiveness in reducing flood risks. Upstream wetlands contribute more effectively to flood reduction than midstream or downstream wetlands, primarily due to their capacity to absorb excess runoff before it reaches major tributaries.
Rejuvenation of wetlands in high-precipitation zones substantially decreases downstream flooding. Moreover, the cumulative effect of multiple wetlands operating under controlled conditions maximises flood resilience, ensuring a sustainable and long-term impact on flood management efforts.
Influence of dynamic wetland management
A critical finding of the research is that static wetlands reach capacity early in the monsoon season, limiting their effectiveness in subsequent flood events. The study proposes a controlled storage release policy that considers precipitation thresholds and wetland ecological needs to optimise flood mitigation. Under this management approach, flood peaks were reduced by up to 6% at the catchment scale and by 28% at the tributary scale. The implementation of controlled wetland management strategies ensures that wetlands remain effective throughout the monsoon season, preventing uncontrolled overflows and mitigating the risk of severe flooding.
Impact on water levels at key cities
Water surface elevation at major cities such as Guwahati, Tezpur, and Dhubri showed significant reductions under the managed wetland scenario. Controlled wetland releases prevented high flood level exceedances in upstream cities such as Dibrugarh and Jorhat. Midstream cities observed significant improvements, with up to a 65% reduction in danger level exceedances. The impact at downstream locations such as Dhubri was less pronounced due to the wider river cross-section, but the controlled releases still contributed to mitigating severe flood levels. This demonstrates the potential of wetlands as an effective flood control measure, particularly when managed dynamically.
Economic and ecological considerations
The study also emphasises the economic and ecological considerations of wetland management. Wetland rejuvenation is identified as a cost-effective nature-based solution (NbS) with long-term socio-economic benefits. Maintaining ecological integrity is crucial, as wetlands support diverse aquatic ecosystems that depend on stable water levels. To sustain these ecosystems while also achieving flood mitigation, wetlands should retain a minimum storage level. Additionally, stakeholder engagement and policy integration are essential for the successful implementation of wetland management strategies, ensuring that economic, environmental, and social benefits are maximised.
Recommendations
Implement a catchment-wide wetland rejuvenation strategy: To maximise flood reduction benefits, it is recommended that wetland rejuvenation efforts focus on upstream and midstream regions. Restoring degraded wetlands should involve increasing surface area by 20-30% and depth by 2-3 meters to enhance storage capacity. This will help increase water retention and slow down the flow of excess water, preventing severe flooding downstream.
Adopt a controlled wetland management approach: A controlled storage-release policy should be developed to pre-emptively release water based on rainfall forecasts. This strategy would enable wetlands to maintain sufficient storage capacity throughout the monsoon season. The use of remote-controlled mechanisms such as gates or siphons can enhance the efficiency of wetland water management, ensuring optimal flood mitigation while maintaining ecological balance.
Enhance monitoring and data integration: Accurate data collection on precipitation, river discharge, and wetland capacity is crucial for refining hydrological models and improving wetland management. Advanced monitoring systems, including satellite and GIS-based tools, should be utilised for real-time wetland management. Such integration would enable authorities to respond proactively to flood risks, ensuring effective intervention strategies.
Incorporate wetland management into regional flood policies: To ensure long-term sustainability, wetland rejuvenation efforts should be aligned with existing floodplain management and climate adaptation strategies. Legal and financial frameworks should be established to support wetland conservation initiatives. Policymakers should consider integrating wetland restoration into regional flood mitigation programs to enhance their effectiveness and secure funding for long-term sustainability.
Increase public and stakeholder engagement: Public awareness of the benefits of wetlands as nature-based solutions for flood resilience should be promoted. Local communities, governments, and private stakeholders should be actively involved in wetland conservation and restoration projects. Participatory approaches will ensure that wetland management initiatives are well-supported and successfully implemented, fostering long-term community engagement and environmental stewardship.
Conclusion
The findings of this study underscore the significant role of hydro-ecological based wetland management in mitigating flood risks in large river catchments such as the Brahmaputra. Rejuvenation and controlled management of wetlands enhance their flood mitigation potential, particularly in high-precipitation zones.
By integrating wetland conservation into regional flood policies and leveraging advanced hydrological modelling, sustainable flood resilience can be achieved. Implementing the proposed recommendations will ensure that wetlands continue to provide critical ecosystem services while protecting communities from devastating floods.