South Fork Dogfish Creek will get gradual makeoverOctober 28th, 2010 by cdunagan
The city of Poulsbo now has a reasonable blueprint for restoring the South Fork of Dogfish Creek as money and volunteers become available. The city is the logical entity to lead the effort, considering that 90 percent of the 700-acre watershed lies within the city limits.
Reporter Brynn Grimley quotes Mayor Becky Erickson in Wednesday’s Kitsap Sun:
“The plan identifies the low-hanging fruit, the individual projects over time that don’t cost a lot of money and that really restore the creek… Over the next four to five years, we hope to find funding and fix these one piece at a time. The idea of salmon spawning throughout Poulsbo and what that means to our heritage, that’s a good thing.”
The battle against pollution in Dogfish Creek has been going on for years under the leadership of the Kitsap County Health District. Much of the focus has been on septic systems and farming practices on the main stem of the creek, which flows down from the north through rural farmlands and housing developments, as well as the east and west forks of the stream.
What struck me about the plan for the South Fork is its clear focus on structure and function — in other words, looking at the needs of salmon. The South Fork Dogfish Creek Restoration Master Plan (PDF xx 8.8 mb) lists these objectives:
- Remove, repair, and replace barriers to fish migration.
- Restore/create off‐channel rearing and high‐flow refuge habitat.
- Increase instream habitat complexity (e.g., install large woody debris, create pools).
- Improve low‐flow water quality conditions (e.g., temperature and dissolved oxygen).
- Improve high‐flow water quality conditions (e.g., sediment and chemical pollutants in stormwater).
- Improve connection to the floodplain (i.e., restore natural planform and reduce channel incision).
- Restore riparian habitat (e.g., restore native plant species, increase interspersion of different plant communities).
- Restore connection to floodplain wetlands.
- Enforce existing regulations that protect stream ecology.
Salmonids — including coho, chum and steelhead — will love those changes, but many of the ideas don’t come cheap. Fortunately, some of the most critical problems — culvert barriers — are being fixed by the Washington Department of Transportation’s widening project on Highway 305.
The issue of flooding is also addressed in the plan, which emphasizes low-impact development (projects that infiltrate stormwater close to where it begins as rainfall).
These objectives are clearly spelled out:
- Increase stormwater detention storage.
- Improve stormwater conveyance.
- Update stormwater standards for new development.
- Retrofit existing development with stormwater treatment and detention facilities.
- Develop basin‐wide programmatic actions to reduce flooding (e.g., maintenance program for storm drains and catch basins, retrofit existing impervious surface area with stormwater detention and treatment facilities).
Over the past 100 years, the loss of vegetation and increased development with hard, imperious surfaces has reduced salmon habitat and increased flooding, according to the report:
“These conditions appear to have caused channel scour and bank erosion in the upper subbasin and sediment deposition in the lower subbasin. The channel scour has resulted in decreased floodplain connectivity, and the sediment deposition has filled pools and created a wide, braided channel form and contributed to increased flooding in the lower subbasin. These changes have degraded instream and riparian habitat for native fish and wildlife species.”
One thing I could not find in the study is an estimate of how many salmon and trout could be supported in the South Fork if the stream were restored to a feasible condition, given its urban setting. I would think that estimate or a qualitative discussion would important for city officials.
As the mayor suggests, the most valuable part of the plan may be the list of projects and rough estimates of cost, allowing these projects to be tackled as money and public support become available.