CAREER: Coupling post-fire vegetation and volumetric sediment regimes in urban Mediterranean systems

San Diego State University Foundation, San Diego CA

Investigators

Abstract

Wildfires are increasing in size and extent across the western United States. Human-ignited fires, drought, large fuel loads, and non-native vegetation have made urban streams and rivers into avenues for fire movement. Very little is known about these new urban fires and the impacts on local ecosystems. The goal of this research is to understand and predict changes in vegetation, soil, and stream processes that occur after fires. Areas adjacent to streams, called riparian zones, are important in controlling the impacts of fires by regulating the release of pollutants and the erosion of soil into streams. Yet these riparian processes are poorly understood in urban stream corridors. Remote sensing methods provide detailed images of the Earth's surface from satellites and airplanes. Examining repeated images through time can allow researchers to document changes in erosion and to relate those changes to differences in riparian vegetation and stream conditions. The data collected from this project can be incorporated into mathematical models to make predictions about erosion and sediment following fires that can lead to poor water quality. The proposed research will include educational and outreach activities with San Diego State University and local community college students. Students from community colleges in San Diego County will be invited to participate in this research and will be encouraged to pursue higher education in science and engineering. This work will also increase community education opportunities and interactions through public seminars and outreach events. Human-ignited fires, drought, large fuel loads, and non-native vegetation have made urban streams and rivers into corridors for fire movement. The increase in human interactions in fire-prone areas can significantly alter hydrologic and sediment yield processes, which can transport contaminants to urban waterways. This research will contribute new fundamental knowledge on short- and long-term post-fire recovery processes in urban Mediterranean stream systems. The goal of this work is to understand coupled sediment and riparian zone interactions using a combination of field, remote sensing, statistical, and modeling approaches to describe and predict post-fire changes. Specific research objectives include: 1) establishing non-linear spatial and temporal relations between vegetation patterns and sediment volume within the upland and riparian zones after fire; 2) coupling the recovery trajectory of in situ volumetric sedimentation and hydrologic response after fires with satellite-based imagery of upland and riparian vegetation; and 3) developing a mass balance model to predict sediment flux following fires due to the evacuation of sediment stored behind vegetation. Light detection and ranging will provide detailed images of the landscape, allowing documentation of the storage and supply of sediment as a function of non-native and native vegetation and hydrologic conditions. Satellite imagery will augment these relationships and document interactions at multiple spatial and temporal resolutions. This information will be incorporated into a mass balance model to predict sediment contributions, which can be a source for degraded water quality following fires. Integrated educational activities include student researchers from San Diego State University and local community colleges, and outreach events to the public and local water agencies. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.