Goals and Objectives of the Restoration
Despite efforts by the planning team to avoid and minimize impacts to waters/wetlands by locating the campus on the hillslope, development of the campus still required the filling of approximately six acres of wetlands. Mitigation was therefore necessary for the project to occur.
While it would have been possible to meet the mitigation requirements on the site without restoring the entire floodplain and channel, the State of Washington made a commitment to environmental enhancement of the site that went beyond that which was strictly necessary from a regulatory standpoint. With environmental enhancement as one of the stated goals of the project, the most logical and consistent approach to meeting the regulatory requirements was to restore the structure and functioning of the North Creek riverine ecosystem on the site.The planning team proposed that North Creek be reconnected to portions of its historical floodplain through creation of a new primary and secondary channel and restoration of approximately 58 acres of riverine and floodplain ecosystem.
The proposed restoration was recognized by the regulatory agencies as more than mitigating for the acres of wetlands lost to campus construction and conditional permits were issued in 1996. Final project approval was granted in June of 1998.
The restoration was guided by the following principles:
- 1. Give due diligence to federal, state, and local regulatory requirements (avoid, minimize, then mitigate).
- 2. Target no net loss of area and/or function.
- 3. Target an on-site, in-kind approach to mitigation.
- 4. Base the restoration design on attainable regional references.
- 5. Target native riverine ecosystem features (i.e., plants and animals) and functions.
- 6. Integrate the forms and functions of natural and campus landscapes.
Design of the restoration began during the master-planning phase of the project. The architectural firm NBBJ on behalf of the HECB hired L.C. Lee & Associates, Inc. to complete a 75% design for the restoration and to obtain preliminary agency approval for the project. When responsibility for project management was turned over to the Washington State Department of General Administration in fall of 1997, NBBJ selected L.C. Lee & Associates, Inc. to lead the team that would finalize the restoration design.
Stream Channel and Floodplain
The riverine ecosystem restoration design was based upon detailed information from reference sites, studies of the current conditions of North Creek basin hydrology, hydrologic modeling, channel constraints, and the ecological potential of the North Creek site. OTAK, the civil engineering firm on the team, had primary responsibility for designing and sizing the channel based on their hydraulic analyses. The channel design also incorporates input from University of Washington fluvial geomorphologists, Dr. Dave Montgomery and Timothy Abbe.
The restored North Creek ecosystem is designed to develop over decades. With particular respect to the new channel system, the restoration is designed to occur with minimal risk; that is, slowly and in logical stages.
Channel and wetland design targets included: (1) maximizing channel length, (2) maximizing contact time between water and wetlands, (3) creating secondary high flow channels, (4) placing large wood in-channel to guide channel alignment and morphology, (5) providing for increased peak flows as a result of urbanization of the North Creek watershed, (6) allowing lateral channel movement within design parameters, and (7) providing visual access from both the campus and highway corridors.
It was decided that natural stream channel morphology would be returned to North Creek by constructing a new channel system that reflected characteristics found at reference sites in the Puget Sound Lowlands. That is, the new stream channel system would be constructed to allow overbank flow to occur approximately once a year. This approach would restore the linkage between channel and floodplain components of the North Creek ecosystem. The new main channel was designed with bed and bank features, meanders, and a variety of in-channel habitats, including pools, riffles, and large wood. Secondary channels were designed to engage at different flow volumes.
Restoration Development Over Time
Restorations of natural ecosystems take a long time. The native forests of the Puget Sound require hundreds of years to reach maturity. Initially the restoration at UWB/CCC will look much like a clear-cut. Canopy closure of trees will not happen for about ten years. At the end of ten years, the site should begin to look like an immature forest. It will take another 20 or 30 years before the restoration site really begins to function fully as a self-sustaining ecosystem. While the restoration is maturing it will be necessary to actively manage the site. Management requirements at the site will be highest during the first three to five years and then gradually taper off. Eventually, all that will be required as routine maintenance.
The federal Clean Water Act Section 404 permit requires monitoring of the site for 10 years following completion of the restoration. This monitoring is designed to ensure that the restoration is indeed progressing towards specified project targets as articulated in the permit. If the restoration is not progressing towards the project targets as required, contingency measures are triggered. For instance, if a severe drought or flood causes significant mortality of planted stock, replanting may be required. At the end of ten years, if project targets are met, the permit conditions will be satisfied.
In addition to monitoring, routine maintenance will be required to ensure the success of the restoration. For the first several years, maintenance will include irrigation of newly planted areas and active weed control. Additional plantings may also be required. Longer term maintenance includes ongoing weed and pest control, cleanup of trash; trail maintenance, and possible thinning.
Educational / Interpretive Opportunities
It was recognized early in the planning phases of the UWB/CCC project, that the restoration could be a valuable educational resource. This is one of the biggest floodplain restorations in the Pacific Northwest and it will undoubtedly attract considerable attention. The restoration design team solicited peer review from members of the UW academic community during the design and construction of the floodplain. It is hoped that this interest will carry forward with a long-term interest and commitment to the site. The restoration area should provide opportunities for research at the university level and teaching opportunities at all levels.