Geographic variation in Puget Sound tidal channel geometry: Developing a tool for restoration planning, design, and monitoring
Presentation Abstract
Effective tidal marsh restoration requires the ability to predict the outcomes of proposed restoration actions. Tidal channels are central elements of marsh hydrodynamics, sediment dynamics, and habitat, so GIS was used to digitize tidal channels from aerial photographs of Puget Sound river delta marshes and develop allometric models of channel geometry that predict the number and size of tidal channels that could develop following marsh restoration through dike breaching or removal. Tidal marsh area was the independent variable for all dependent channel planform metrics. Tidal channel allometry showed similar scaling exponents for channel planform metrics throughout Puget Sound, which simplified comparisons between locations. Y-intercepts of allometric relationships showed geographic variation in channel geometry, which multiple-regression analysis indicated was associated with tide range and storm-significant wave height. Channel size and complexity were positively related to tide range and negatively related to wave height. Closer examination of four case studies, each with paired regions of similar tide range and contrasting wave environments, further indicated wave environment affected channel geometry. Wave-mediated sediment delivery may be the mechanism involved, with wave-sheltered areas experiencing relative sediment deficits such that some tidal marshes in Puget Sound are already suffering sea level rise impacts that are reflected in their channel network geometry. Allometric models of channel planform can provide useful guidance for marsh restoration planning, design, and monitoring. For example, scaling exponents > 1 indicate non-linear cumulative effects of restoring tidal marsh area on total channel length and surface area, which likely has numerous implications for decision making, including asset allocation among and within potential restoration projects, and negotiations with stakeholders.
Session Title
Session S-05F: Ecosystem Restoration: Geomorphic Context, Design Considerations, and Success Stories
Conference Track
Restoration
Conference Name
Salish Sea Ecosystem Conference (2014 : Seattle, Wash.)
Document Type
Event
Start Date
1-5-2014 10:30 AM
End Date
1-5-2014 12:00 PM
Location
Room 602-603
Genre/Form
conference proceedings; presentations (communicative events)
Contributing Repository
Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.
Subjects – Topical (LCSH)
Salt marsh ecology--Washington (State)--Puget Sound; Geographic information systems--Washington (State)--Puget Sound; Tidal currents--Washington (State)--Puget Sound; Restoration ecology--Washington (State)--Puget Sound
Geographic Coverage
Salish Sea (B.C. and Wash.); Puget Sound (Wash.)
Rights
This resource is displayed for educational purposes only and may be subject to U.S. and international copyright laws. For more information about rights or obtaining copies of this resource, please contact University Archives, Heritage Resources, Western Libraries, Western Washington University, Bellingham, WA 98225-9103, USA (360-650-7534; heritage.resources@wwu.edu) and refer to the collection name and identifier. Any materials cited must be attributed to the Salish Sea Ecosystem Conference Records, University Archives, Heritage Resources, Western Libraries, Western Washington University.
Type
Text
Language
English
Format
application/pdf
Geographic variation in Puget Sound tidal channel geometry: Developing a tool for restoration planning, design, and monitoring
Room 602-603
Effective tidal marsh restoration requires the ability to predict the outcomes of proposed restoration actions. Tidal channels are central elements of marsh hydrodynamics, sediment dynamics, and habitat, so GIS was used to digitize tidal channels from aerial photographs of Puget Sound river delta marshes and develop allometric models of channel geometry that predict the number and size of tidal channels that could develop following marsh restoration through dike breaching or removal. Tidal marsh area was the independent variable for all dependent channel planform metrics. Tidal channel allometry showed similar scaling exponents for channel planform metrics throughout Puget Sound, which simplified comparisons between locations. Y-intercepts of allometric relationships showed geographic variation in channel geometry, which multiple-regression analysis indicated was associated with tide range and storm-significant wave height. Channel size and complexity were positively related to tide range and negatively related to wave height. Closer examination of four case studies, each with paired regions of similar tide range and contrasting wave environments, further indicated wave environment affected channel geometry. Wave-mediated sediment delivery may be the mechanism involved, with wave-sheltered areas experiencing relative sediment deficits such that some tidal marshes in Puget Sound are already suffering sea level rise impacts that are reflected in their channel network geometry. Allometric models of channel planform can provide useful guidance for marsh restoration planning, design, and monitoring. For example, scaling exponents > 1 indicate non-linear cumulative effects of restoring tidal marsh area on total channel length and surface area, which likely has numerous implications for decision making, including asset allocation among and within potential restoration projects, and negotiations with stakeholders.
