Elizabeth Tellman, MESc

2013 TRI Fellow in El Salvador

Ecosystem Services for Disaster Risk Reduction: Modeling the effects of land use on freshwater flood mitigation in El Salvador

My research measures and maps the impact of urbanization and deforestation on flood risk in El Salvador.  I am comparing flooding over time in two urban watersheds to one forested watershed. For each watershed, I rely on remote sensing to map land use in 5 major storms over the past 15 years, and household surveys to understand maximum flood depth at various locations for each storm.  I surveyed river cross-sections and sediment samples to understand both the geomorphology and infrastructure of the river system in each watershed. Finally, I have precipitation and elevation information for my entire region of study. All of this data is used to create a computer flood model of each watershed, calibrated on historic floods. This allows me to understand how changing land use has affected stream flow and flood patterns historically. The model is then used to run future scenarios of land use and climate change, showing flooded area and depth for each situation. Visualizing and understanding the differences in future scenarios of flood risk will help the NGO I work with, ACUA (Association of Community Water and Agriculture) develop better watershed management plans by optimizing forest protection where it is most crucial to mitigating flood risk.


Land Use Change and Ecosystem Service Sheds: Where Does Deforestation Impact Flood Mitigation in El Salvador?