Aishwarya Rishitha Nagireddy

UR3596

UUR20009

Nature-based solutions For Hybrid Riverine Ecosystems: Adapting to Water Stress in South Asian Monsoon Climates - The Case of Chandrabhaga Catchment in Ahmedabad

South Asia’s monsoon-driven hydrological regime presents significant challenges to urban resilience, particularly in hybrid riverine ecosystems where fluctuating moisture conditions, unregulated urbanization, and ecological fragmentation exacerbate flood vulnerability. While Nature-based Solutions (NbS) have been widely studied in temperate climates, their application in monsoon-affected urban environments remains underexplored.

 This research advances a multi-scalar methodology for assessing flood vulnerability and NbS potential within Ahmedabad’s hybrid urban riverine systems, bridging ecological restoration with urban resilience. The study employs a Grid-Based Additive Overlay Framework to assess flood vulnerability and identify priority zones for NbS within the Chandrabhaga Catchment, Ahmedabad. The methodology operates at two scales: macro (5 km × 5 km) grids to assess broad flood susceptibility across the urban-river interface, and micro (2.5 km × 2.5 km) grids for detailed land-use classification and flood risk evaluation. Each grid is analyzed using datasets from ICLEI, GIS mapping, and development plans, considering factors such as flood potential, built density, and land-use patterns. A composite vulnerability score is assigned to each microgrid, helping pinpoint the most critical areas for targeted intervention. Following the grid analysis, a criticality matrix is developed to assign land-use types to be activated at specific return periods based on their criticality threshold, using the Flood Vulnerability Index (FVI). Sub-site typologies of land uses are codified to calculate flood risk scores, which are then used to determine flood allowances. Based on these assessments, two sites with extreme flood allowances one with high flood tolerance and the other with low flood tolerance—are selected to explore the potential for implementing NbS.

NbS applications are demonstrated at these sites, with each solution tailored to address the site-specific hydrological challenges. The study also considers future land-use change scenarios, assessing how evolving developments might influence flood dynamics. By simulating these changes, the research evaluates the effectiveness of NbS in reducing surface runoff, mitigating flash floods, and ensuring sustainable water management. Ultimately, the findings will demonstrate how NbS can preserve hydrological functions, reduce flood risks, and enhance urban resilience, while providing ecological benefits. The results contribute to urban planning and policy by offering a replicable framework for integrating NbS into monsoon-prone cityscapes across South Asia, bridging flood management with ecological restoration in urban riverine contexts.
 
Keywords:(NbS), flood vulnerability index, urban riverine systems, monsoon resilience, flood risk and flood allowance, adaptive flood management  

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Framing the Context Introduction to the study, situating it within the broader (URP) while foregrounding the global climate crisis and its cascading impacts on urban flood dynamics.

Situating Nature-Based Solutions (NBS) Establishing the theoretical and spatial foundation for NBS, this slide contextualizes Ahmedabad as a volatile urban landscape and introduces the Chandrabhaga rivulet as a case of hybrid riverine ecologies.

Aim, Scope, and Problem Focus Defining the research intent, core problem areas, and boundaries of investigation, this slide outlines the study’s objectives and relevance within contemporary urban flood management discourse.

Multi-Scalar Methodological Framework Presentation of a tiered methodological approach across macro (10x10 km, 5x5 km), meso (5x5 km, 2.5x2.5 km), and micro (<1 sq. km) scales to analyze, decode, and intervene within the urban flood-prone landscape.

Land Use Typologies and Criticality Matrix Classification of land uses based on their hydrological and ecological behavior to generate a criticality index that informs placement within the Flood Activation Pyramid.

Sub-Typologies of Land Use Further granularity of the landscape through the coding of land use sub-types to refine spatial understanding and tailor NBS interventions accordingly.

Flood Risk Coding and Spatialization Mapping flood susceptibility by integrating coded land uses with hydrological parameters, translating data into spatial risk zones for targeted intervention.

Flood Allowance and Water Behavior Analytical visualization of water behavior in varied terrains and land uses, helping define thresholds for flood allowance and performance-based design.

Micro-Scale NBS Application Strategy Site selection and strategic application of NBS at the micro-scale, drawing from URP and DRP precedents, and aligned with projected land use transitions under Ahmedabad’s 2021 Development Plan.

Demonstration, Impact, and Way Forward Comparative analysis of surface runoff before and after NBS implementation, concluding with reflections on research limitations, outcomes, and future directions for integrated flood resilience planning.