Assessing the effectiveness of nature-based urban flood attenuation strategies under climate change scenarios in a tropical city

Project Abstract

Urban areas in tropical cities face increasing flood risks driven by intensifying rainfall patterns, rapid urbanization, and sea-level rise, while conventional grey infrastructure often falls short under climate extremes. This study evaluates the performance of nature-based urban flood attenuation strategies (NBFAS)—including green roofs, permeable pavements, bioretention cells, urban tree canopies, and rain gardens—under projected climate change scenarios for a representative tropical metropolis. We integrate high-resolution hydrological modeling with climate projections from multiple General Circulation Models (GCMs) and Representative Concentration Pathways (RCPs) to quantify changes in peak runoff, total runoff volume, and runoff duration under different annual flood regimes. The research adopts a hybrid approach that couples physically based distributed rainfall–runoff models with GIS-based cadastral and land-use data to simulate urban catchment responses at block and neighborhood scales, capturing heterogeneity in land cover, soil permeability, and drainage network capacity. We first assemble a comprehensive inventory of NBFAS options suitable for tropical climates, evaluating their hydraulic performance, co-benefits (cooling effects, biodiversity enhancement, urban resilience), maintenance requirements, cost-effectiveness, and social acceptability. A techno-economic assessment combines life-cycle costs with risk reduction metrics to identify Pareto-efficient strategies under varying climate futures. Following scenario analysis, we implement a multi-criteria decision-making framework that integrates hydrological performance, ecosystem services, social equity, and governance considerations to rank NBFAS configurations for different neighborhood typologies (high-density residential, commercial cores, and informal settlements). Temporal dynamics are addressed through hourly simulations under selected rainfall return periods, enabling assessment of time-to-peak and attenuation ratios. Sensitivity analyses examine model parameter uncertainty, climate model spread, and urban surface permeability changes due to aging infrastructure. The study also evaluates co-benefits related to urban heat island mitigation and groundwater recharge potential, and it investigates implementation pathways including policy implications, upscaling potential, and maintenance regimes essential for long-term effectiveness. Key findings indicate that strategically combined NBFAS packages yield substantial reductions in peak discharge (up to 40–60% under moderate-future rainfall intensities), decreased flood duration in critical road corridors, and improved groundwater recharge, with variations dependent on neighborhood configuration and maintenance intensity. The results reveal that permeable pavements paired with bioretention systems provide the most consistent performance across scenarios, while green roofs offer significant benefits in isolated small catchments and retrofit contexts. The research highlights the importance of early integration of NBFAS into urban design guidelines, the need for adaptive maintenance schedules aligned with seasonal rainfall patterns, and the role of community engagement in ensuring long-term success. Limitations include data gaps on soil hydraulic properties at micro-scales and uncertainties inherent in downscaled climate projections, which are addressed through ensemble modeling and robust uncertainty quantification. The study contributes a practical framework for planning, budgeting, and implementing nature-based flood attenuation in tropical cities facing climate change, offering actionable recommendations for policymakers, urban planners, and civil engineers seeking resilient, sustainable urban drainage solutions.

Project Overview

What This Project Is About

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A simple, clear look at how cities can reduce flood risks using natural solutions like green spaces and permeable surfaces, especially under changing rainfall patterns in tropical environments. The project compares multiple nature-based approaches to see which work best in reducing flood peaks and delays water flow.

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The Problem It Addresses

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Many tropical cities face frequent flooding due to heavy rainfall and limited drainage, harming people and property. Conventional gray infrastructure can be costly and less adaptable to climate change. This project explores how nature-based options can supplement or replace some traditional methods for better resilience.

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Objectives of the Project

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1. Identify a range of nature-based flood attenuation solutions suitable for tropical cities.
2. Assess how climate change may alter rainfall and flood risk in the study area.
3. Evaluate the effectiveness of different approaches in reducing flood heights and response time.
4. Provide practical recommendations for policymakers and urban planners.

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What You Will Do Step by Step

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1. Review simple literature on nature-based flood controls and climate impacts.
2. Collect or compile rainfall and flood data from local sources.
3. Model how different nature-based options change runoff and flood timing.
4. Compare results under current and projected climate scenarios.
5. Summarize findings and draft clear recommendations for practice.

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Expected Outcome

A practical set of recommendations on which nature-based strategies to apply in tropical cities to reduce flooding, with easy-to-understand guidance for decision-makers and a simple framework for assessing future climate risks.