A Nature-Based Solutions Planning Framework for Arid Cities

Abstract

As aridity continues to increase in the world, with nearly 300 large cities projected to face increasing water scarcity issues by 2050, Nature-based Solutions (NbS) offer a unique multifunctional approach to addressing the severe environmental pressures in these contexts. While existing NbS planning frameworks provide a robust structure and guidance for city-planners, there is a gap in tailoring these frameworks to the context of hot arid cities, given the different environmental and socio-economic conditions. Against this backdrop, this research seeks to answer how can existing NBS planning frameworks be contextualized to address the specific challenges in hot arid cities?

The methodology used to answer this question employed a qualitative analysis of existing NbS, Urban Planning and Sustainable Urban Planning frameworks, coupled with a cross-case comparative analysis of implemented NbS interventions in arid cities.

Findings reveal a dominance in greening models in NbS, leaning towards addressing visible short-term stressors – like addressing heat stress using increased vegetation– with little consideration to underlying environmental stressors – like limited water supply. This mismatch is exacerbated by limited research engagement to adapt NbS interventions to the local ecosystem processes. The study also reveals how interactions between lead, funding and implementing actors impact NbS design and deployment across different scales and spatial contexts, with city-wide interventions skewed towards centralized governance systems, and smaller-scale interventions comprising higher modes of stewardship and participation with the local community.

By synthesizing insights from 94 global case studies and existing planning literature, the study offers a Contextualized NbS Planning Framework (C-NbS-F) for hot arid cities, and a prototype decision-support tool to help planners shift from visible "greening" symptoms to underlying hydrological limits.

Lastly, this thesis contributes to enhancing urban resilience against progressing aridification due to climate change, by generating transferable lessons and strategies for a more water-scarce future.