Using Nature-Based Solutions for Flood Resilience
This project in Guayaquil's Febres Cordero parish explores nature-based solutions (NBS) to enhance flood resilience. Using the CRIDA methodology, the initiative involves local and international partners, fostering a collaborative, bottom-up approach with societal actors and governmental institutions.
Contexte
Guayaquil, Ecuador's delta city, is highly vulnerable to flooding, with projections indicating significant economic losses by 2050. The city¡¯s population of 2.7 million faces frequent flood events, severely impacting daily life. The Febres Cordero parish, identified as particularly vulnerable, struggles with high population density, poverty, and limited healthcare access, compounded by biophysical conditions like its proximity to the Salado Estuary and extensive impermeabilization.
Actions
In July 2018 local societal leaders and governmental institutions related to water management, environment, urban planning, and risk management participated in a stakeholder workshop to establish the decision context, CRIDA Step 1. A problem analysis of floodings as well as the common vision for the future of FC parish were analyzed and defined.
Next up, in CRIDA Step 2, a bottom-up vulnerability assessment was conducted to evaluate the impact of urban flooding under climate change scenarios, including altered precipitation patterns and sea level rise. An urban flood model was created using terrain and stormwater drainage data, considering precipitation return periods (1, 10, 50, and 100 years) and rainfall durations (3, 5, and 18 hours). Sea level anomalies were incorporated to assess their effect on the stormwater system's capacity. Additionally, economic impact of floods were estimated through interviews and census data. Residential areas faced losses of USD $298-$333 per home (flood levels of 20-50 cm), while commercial sectors saw losses of USD $29-$41 per business.
CRIDA Step 3 entails the listing of possible adaptation actions. Flood management in the city typically focuses on expanding stormwater drainage. However, in line with a vision for a greener Febres Cordero parish and flood resilience, nature-based solutions (NBS) were explored to complement existing flood management efforts. These options included green and blue measures to improve water infiltration and retention.
A selection of these measures was integrated into three alternatives for redesigning public spaces in Febres Cordero parish, ranging from low to high-level interventions (i.e., from gray infrastructure to green solutions). These alternatives were presented to societal and institutional actors in workshops, where the extent of flooded areas and flood drainage time were used as key metrics to evaluate improvements in flood resilience. This can be seen as CRIDA Step 4, the adaptation pathways evaluations, and CRIDA Step 5, the institutionalization of the decisions.
Outcomes
The CRIDA project¡¯s outcomes revealed that the alternative featuring mid-level interventions on public space was selected as the most viable solution by local governmental institutions and societal actors. Key municipal departments, including those focused on transportation, green spaces, public works, and stormwater management, confirmed the feasibility of these actions in line with future urban development plans. This validation showed that nature-based solutions for flood resilience could be integrated with existing infrastructure and municipal plans. The participatory process not only increased the likelihood of adopting these solutions but also facilitated the institutionalization of the CRIDA approach through enhanced collaboration across departments and institutions, promoting a more resilient city.