Assessing the effectiveness of urban green infrastructure in mitigating flood risk and urban heat in rapidly growing cities: A case study approach

Project Abstract

Urbanization in rapidly growing cities intensifies flood risk and urban heat islands (UHI) due to impervious surfaces, reduced vegetation, and altered hydrological cycles, necessitating evidence-based deployment of urban green infrastructure (UGI). This study evaluates the effectiveness of UGI configurations—including green roofs, permeable pavements, bioswales, urban trees, and pocket wetlands—in mitigating flood risk and reducing ambient temperatures across different urban morphologies. A mixed-methods approach integrates hydrological modelling, microclimate simulations, remote sensing analysis, and empirical field measurements to quantify performance under multiple rainfall return periods (10-, 25-, and 100-year events) and seasonal temperature variations. The research comprises four interconnected objectives (1) to quantify the hydrological impact of UGI on peak discharge, runoff volume, and infiltration rates using calibrated distributed rainfall-runoff models and urban catchment data; (2) to assess UGI effects on thermal comfort and heat load by analyzing surface and air temperatures, heat fluxes, and diurnal temperature ranges through high-resolution thermal imaging, ground-based sensors, and meteorological data; (3) to identify synergistic vs. trade-off conditions between flood mitigation and heat reduction across diverse land-use types, street canyons, and building densities; and (4) to develop a decision-support framework that optimizes UGI design parameters (size, density, configuration, and maintenance) under constraints of cost, land availability, and social acceptability. A case study area spanning quadrants of a rapidly expanding metropolitan region with heterogeneous housing typologies and land tenure is selected to ensure generalizability while capturing local context. Data sources include LiDAR-based digital elevation models for hydrological routing, high-resolution satellite vegetation indices, sensor networks capturing temperature, humidity, and soil moisture, and historical flood and heat event records. The analysis employs (a) hydrological modelling with SWMM/MIKE URBAN to simulate rainfall-runoff responses with and without UGI scenarios; (b) urban microclimate modelling using ENVI-met and RayMan to estimate UHI intensity reductions attributable to green corridors and evaporative cooling; (c) spatial statistics and scenario analysis to identify critical thresholds where UGI yields diminishing returns; and (d) cost-benefit and social acceptance assessments to evaluate long-term sustainability. Expected outcomes include quantifiable reductions in peak discharge by up to 25–40% in targeted streetscapes, substantial UHI attenuation during heatwaves (mean radiant temperature decreases of 2–4°C in populated areas), and a robust optimization framework that guides policymakers and planners in prioritizing UGI investments. The study will also elucidate context-dependent performance drivers such as soil permeability, rainfall intensity, maintenance regimes, and community engagement, thereby contributing actionable guidelines for integrating UGI into urban resilience planning for flood and heat mitigation in rapidly urbanizing environments.

Project Overview

What This Project Is About

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A plain-language overview of how urban green spaces can reduce floods and heat in cities that are growing quickly, and what a case study will look at to learn from real examples.

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The Problem It Addresses

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Cities are expanding faster than they can plan for flood risk and heat management. Traditional gray infrastructure often fails during heavy rain and heat waves. This project investigates how nature-based solutions can help, and why it matters for safety, comfort, and sustainability.

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Objectives of the Project

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1. Understand what urban green infrastructure (UGI) is and where it fits in city planning.
2. Assess how UGI helps reduce flood risk and urban heat in a real city case study.
3. Identify key factors that make UGI effective or limited in rapidly growing areas.
4. Provide practical recommendations for planners and communities.

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What You Will Do Step by Step

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1. Review simple background material on floods, heat in cities, and UGI concepts.
2. Choose a city or district with available data for a detailed look.
3. Collect information on parks, permeable surfaces, wetlands, and tree cover.
4. Analyze how these features relate to flood events and temperature data.
5. Compare areas with and without UGI to see differences.
6. Discuss practical challenges like maintenance and costs.

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Expected Outcome

A clear set of findings on which UGI features work best in the chosen city, along with simple recommendations for improving flood resilience and cooling, even for cities with limited budgets.