Abstract: Closing Plenary Session 8:30 am (BACK)


Geomorphic Restoration: Twenty Years After

Barry Southerland, PhD
National W2Q Fluvial Geomorphologist, CPESC#514
USDA-Natural Resources Conservation Service
Portland, OR

In 1996 Geomorphic Restoration was not common on the landscape.  There were very few practitioners completely re-constructing and re-establishing multiple meander wavelengths to the dimension, pattern, and profile of the most probable form.  Two such projects to demonstrate restoration of a braided aggraded system and an incised system were proposed and planned in the Blue Mountains of Washington State in the Asotin Creek Watershed as part of the Model Watershed Salmon Habitat Recovery Program.  A third project involving extensive meander reconstruction was completed 7 years later. Despite skepticism and reluctance by permitting agencies and technical staff from within, two project went forth in natural channel restoration, one in a braided aggraded system and another in an incised system, specifically chosen by the practitioner to demonstrate two extreme scenarios for natural channel restoration.  After several months of field survey, analysis, planning, and design the project went out for technical review, followed by permitting, and was scrutinized vigorously by engineers and biologists.  At one point one of the design reviewers would not accept the natural channel profile component because of the reintroduction of profile facets such as pools, glides, riffles and runs.  The design was approved and the practitioner-designer was the construction foreman for implementation.  The two projects: the J-Bar Ranch meander reconstruction located on the South Fork Asotin Creek and the Frank Koch meander reconstruction on the mainstem of Asotin Creek were implemented in 1997 and 1998, respectively. Twenty years later both projects have been recognized as prime examples of floodplain reconnection, salmon habitat recovery, and a self-maintaining hydraulic geometry within the most probable form. Both projects have maintained their dimension, pattern, and profile while transporting load in a stable manner.  The goal of convincing an agency and multiple bureaucracies that a channel can be reconstructed to its most stable probable form and survive flood stages was accomplished.  This presentation illustrates the long-term positive physical and ecological benefits of implementation of sound geomorphic restoration principles, twenty years after.  Salmonid redds and adult resident populations with a healthy community of benthic macroinvertebrates and riparian forest dependent species are now abundant on reaches were they were lost in 1997.