Dr. Sarah Praskievicz (Geography, Environment and Sustainability) received new funding from the National Science Foundation for the project “Large Woody Debris in Low-Gradient Floodplain Rivers: Spatial Distribution, Physical Controls, and Geomorphic Effects.”
This research seeks to characterize the spatial distribution of large woody debris (LWD) in low-gradient floodplain rivers with fine-grained substrate, the physical controls on LWD recruitment and transport, and the effects of LWD on fluvial geomorphology. LWD (generally defined as pieces of wood at least 1 m in length and 10 cm in diameter, located in the active channel) has long been recognized as a significant driver of physical and ecological processes in river systems. Nevertheless, most knowledge of LWD in rivers is based on studies of small to medium-sized rivers in steep headwater catchments in coniferous forests, notably in the Pacific Northwest and Rocky Mountains of the United States, or in large gravel-bed rivers, such as in Europe. Historical records indicate that large LWD accumulations were once found on most low-gradient forested floodplain rivers, and studies indicate those wood accumulations were significant in fluvial processes and form. More recently, those loads have been reduced by human activities, but major LWD accumulations are still found in some rivers.
Given these findings, a systematic analysis of LWD dynamics and their geomorphic consequences in low-gradient floodplain rivers with fine substrate is warranted. By integrating hydrological, geomorphological, and ecological processes, this research contributes to understanding of coupled landscape and ecosystem dynamics.
The project will address the following research questions:
- What is the spatial distribution of LWD frequency and volume at (a) reach and (b) regional scales?
- What are the physical controls on (a) LWD recruitment and (b) LWD transport?
- What are the effects of LWD on channel process and form?
The research questions will be addressed through a combination of field measurements, remote sensing, tracking of LWD, and statistical and physically based modeling.
Praskievicz also received new funding from the University Corporation of Atmospheric Research for the project “Post-Wildlife Debris-Flow Runout and Inundation Mapping Using Geospatial Analysis.”
The overall goal of the project is to contribute to enhanced resilience of communities to post-wildfire debris flows by creating a geographic information systems (GIS)-based mapping workflow that forecasts the likely runout lengths, paths, and inundated areas. To achieve this goal, the following specific objectives will be addressed:
1. Apply a topographically based debris-flow runout model to >200 wildfires that have occurred since 2016 in seven U.S. states to develop forecasts of runout lengths, paths, and inundated areas.
2. Evaluate model accuracy using observed data on landslide occurrence and extent.
3. Develop tools (a web map and Python script) designed to facilitate the use of the model by emergency managers to enhance the resilience of communities to post-wildfire debris flows.
Methodology:
Use of USGS Post-Wildfire Debris-Flow Hazard Assessments
The project is intended to extend the existing post-wildfire debris-flow hazard assessments conducted by the USGS. All events included in the runout modeling as part of this project will be events that were also included in USGS assessments. The reason for this overlap between assessments is threefold: 1) the USGS takes a comprehensive approach to assessing most wildfires in the United States that are likely to result in enhanced debris-flow hazard; 2) some of the data compiled and modeling done by the USGS will be used as inputs to the runout modeling; and 3) runout modeling is a natural extension of the probability/volume modeling in the USGS assessments.
