mapping bluffs and beaches to quantify sediment supply
300px|leftThis project will help ESRP begin to understand how much sediment input is needed to sustain coastal processes and maintain nearshore ecosystem functions within individual drift cells. Baseline boat-based lidar surveys collected as part of this project will establish current physical shoreline conditions. Geomorphology and habitat metrics can be used to strategically prioritize restoration projects and assess restoration effectiveness.
Sediment supplied from eroding bluffs is important for sustaining Puget Sound beaches and the nearshore ecosystem. Under present shoreline development trends and rising sea levels, sediment supply is among the most at-risk service, while intact beaches and the connectivity of nearshore habitats are among the most difficult to restore. Yet sediment supply rates remain unknown and their effects on beach structure and ecosystem services are only conceptually understood.
This project involved the collection of high-resolution bluff and beach topographic data that can be used to quantify physical aspects of the coastal landscape, including morphology, shoreline armoring, and habitat. The project demonstrates the usefulness of boat-based lidar technology to map drift cells efficiently, with sub-decimeter accuracy and detail. The horizontal-look angle of the mobile laser scanner provides an advantageous view of the coastline, particularly for bluff-backed beaches common to the Salish Sea.
High-resolution digital elevation models and point clouds can be used to detect physical changes in morphology and habitat as needed for monitoring restoration project effectiveness, to understand how much sediment input is needed to sustain beach functions, and to strategically prioritize drift-cell restoration. Morphological and ecological metrics can be extracted from the data, such as bluff toe elevation, back-beach width, overhanging riparian vegetation, large woody debris, beach wrack, and shoreline armor dimensions.
While this data collection effort can only provide one snapshot in time, repeat surveys of the same sites in the future can help us answer key questions about the spatial and temporal variability of beach structure, bluff supply rates, and downdrift effects of sediment input or barriers to sediment transport. As more data is collected, we hope to (1) gain a better understanding of beach response due to altered sediment supply, (2) determine bluff sediment delivery rates, (3) evaluate effectiveness of beach restoration measures, and (4) characterize key linkages between physical and ecological processes.
Relationships
- related to: beaches
- related to: Elwha Drift Cell
- related to: Mapping Bluffs and Beaches to Quantify Sediment Supply 2021
- related to: Web-Based Viewer of Beach Topographic Data
Source: mapping bluffs and beaches to quantify sediment supply on Salish Sea Wiki