Estimating Combined Effects of Climate Change and Land Cover Change on Water Regulation Services of Urban Wetlands in Valdivia, Chile

• Published in: Earth's future Vol. 12; no. 5
• Main Authors: Sauer, J., Grimm, N. B., Barbosa, O., Cook, E. M., Mustafa, A., Kunkel, K., McPhearson, T., Ballinger, A.
• Format: Journal Article
• Language: English
• Published: Bognor Regis John Wiley & Sons, Inc 01.05.2024; Wiley
• Subjects: Cities; Climate change; Climate effects; Climatic data; Drainage; Drainage systems; Environmental regulations; Environmental restoration; Environmental risk; Extreme weather; Flood management; Flood peak; Flood risk; Flooding; Floods; Hydrologic data; hydrology; Infrastructure; Land cover; Management systems; Precipitation; Precipitation data; Rain; Rainfall; Rivers; scenarios; Storm damage; Storms; Stormwater; Stormwater management; Urban areas; Urban development; Urban drainage; urban flooding; urban wetland; Water shortages; Watersheds; Wetlands; Chile
• ISSN: 2328-4277; 2328-4277
• DOI: 10.1029/2023EF003801

The relationship between cities and wetland cover varies across the globe, with some cities converting wetlands to low‐ and high‐density urban cover and others preserving, conserving, or restoring wetlands, or constructing new ones. However, the scientific literature lacks studies relating changes in systemic flood risk in an urban stormwater management systems to changes in wetland cover. Furthermore, whether and how such relationships are affected by changing storm intensity under climate change is unknown. We present a case study on the effects of changes in urban wetland extent and storm intensity on flooding in an urban drainage system in Valdivia, Chile, under several co‐produced future scenarios and historical trends of development. We used data derived from stakeholder workshops and historical landcover to determine four plausible scenarios of urban development, plus one business‐as‐usual scenario, in Valdivia through the year 2080. Additionally, we used historical precipitation data and downscaled climate data to estimate event rainfall from extreme storms in the year 2080. We found that system flood volume and time the system was flooded increased with increasing wetland loss and rainfall volume. Mean rate and hour of peak discharge were unaffected by wetland loss. Infiltration's relative role in reducing flooding diminished as wetland loss increased. Cities may still experience dangerous and/or unacceptable flooding even with extensive wetland coverage and will likely need to pair conservation with additional improvements in their stormwater management systems and contributing watersheds. Plain Language Summary Cities are growing and the decisions that cities make about what they will either build in or exclude from their environments may put them at greater risk of flooding. Decisions to destroy wetlands to make room for new developments may be major causes of this greater flood risk. Flood risk in cities may also increase as the climate continues to change. Flooding severity might be reduced by taking advantage of or restoring natural wetlands, or even by constructing new wetlands. In Valdivia, Chile, a city with extensive wetland cover, we had city employees and community members create positive scenarios of development in Valdivia through the year 2080. Additionally, we used climate models to estimate rainfall volume during an extreme storm event in the year 2080. We modeled how the scenarios would change the wetlands in the city, and how those changes might in turn change the amount of flooding the city experiences under climate change. We found that flooding was worse in scenarios where more wetlands were lost than in scenarios where fewer wetlands were lost. We find clear benefits in conserving, restoring, and/or constructing wetlands to reduce flooding now and into the future. Key Points System flood volume increased with inland urban wetland loss under present‐day and future extreme storms The contribution of infiltration to flood mitigation decreased with wetland loss and overall wetland area Visions of urban development created in stakeholder workshops resulted in lower flood risk than default development pathways