Abstract Title

Session S-05F: Ecosystem Restoration: Geomorphic Context, Design Considerations, and Success Stories

Keywords

Restoration

Start Date

1-5-2014 10:30 AM

End Date

1-5-2014 12:00 PM

Description

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.

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May 1st, 10:30 AM May 1st, 12:00 PM

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.