Design, implementation and evaluation of urban rainwater harvesting systems for resilience

Thesis Abstract

Urban rainfall patterns and increasing flood risk, coupled with strained urban water supply, underscore the need for resilient water governance and efficient stormwater management in rapidly urbanizing cities. This study addresses the design, implementation, and evaluation of urban rainwater harvesting (RWH) systems as a strategic component of urban resilience, integrating technical performance, user acceptance, and policy alignment to reduce vulnerability to droughts and variability in water supply. The aim is to develop a scalable RWH framework that enhances water security, supports flood mitigation, and improves urban livability. Specific objectives are (i) to assess hydrological potential and performance of pilot RWH installations across diverse urban micro-catchments; (ii) to optimize system design parameters (catchment area, storage capacity, filtration, and distribution) for four representative land-use types; (iii) to evaluate socio-economic and behavioral determinants of RWH adoption among residential and commercial stakeholders; (iv) to examine governance, financing, and regulatory factors affecting implementation at neighbourhood scales; and (v) to synthesize design guidelines and policy recommendations for resilient urban water systems. The methodology adopts an embedded mixed-methods design underpinned by realism and complexity theory. The study will be conducted in three metropolitan districts with varying rainfall regimes and infrastructure maturity, targeting a total population of approximately 1.2 million residents. A stratified random sample of 600 households and 40 commercial facilities will be selected to implement and monitor RWH systems over 24 months. Data collection instruments include calibrated flow meters and storage level sensors for quantitative hydrological data; structured questionnaires and semi-structured interviews for socio-economic and behavioral insights; and focus group discussions with neighborhood associations for governance perspectives. Instrument validity will be established through pilot testing and expert review, with reliability assessed via Cronbach’s alpha for survey scales (target ?0.7) and test–retest procedures. Descriptive statistics, regression analyses (multiple and logistic), time-series analysis, and ANOVA will be employed to quantify performance and adoption determinants. A system-dynamics model will simulate long-term resilience impacts under multiple climate scenarios, while a thematic analysis will interpret qualitative data to uncover perceived barriers and enablers. The study will adopt the Theory of Planned Behavior and the Diffusion of Innovations framework to interpret adoption dynamics, complemented by the Resilience Theory lens to assess systemic impacts. Key expected findings include (a) quantified performance metrics of RWH systems across residential and commercial scales, with average annual potable-water Replacement Rates (PWR) ranging from 18% to 42% and total annual runoff capture efficiencies of 60–85% depending on roof area and storage sizing; (b) a design optimization curve identifying diminishing returns beyond 20 m3 storage for typical urban dwellings and 50–100 m3 for commercial properties, with recommended configurations for four urban land-use archetypes; (c) significant associations between perceived behavioral control, social norms, and actual RWH uptake, with financial incentives and technical guidance emerging as critical determinants; (d) governance and policy barriers including permitting complexity, upfront capital costs, and maintenance responsibilities, alongside effective financing models such as performance-based subsidies and micro-lease schemes; and (e) a validated urban resilience framework showing reduced flood peak runoff, lower dependency on centralized supply during drought events, and improved blue-green infrastructure synergies. The study contributes to knowledge by integrating engineering design, behavioral science, and urban policy to produce a holistic resilience-enhancing model for RWH in cities. It provides empirical evidence on performance, adoption determinants, and governance pathways, culminating in context-sensitive design guidelines, cost-benefit benchmarks, and scalable policy recommendations. The main conclusion is that urban RWH systems, when designed with appropriate storage sizing, stakeholder engagement, and enabling governance, can meaningfully bolster water security and flood resilience in metropolitan contexts. Recommendations include adopting standardized design protocols for different land uses, simplifying permitting processes, implementing targeted financial incentives, and institutionalizing routine performance monitoring to sustain long-term resilience gains.