During the last 12 years the Lower Nehalem watershed council and its partners have conducted a series of studies that have produced considerable information on conditions in the Nehalem watershed. These studies include:
Collectively these studies have shown that salmon production and survival in the Lower Nehalem is limited by reduced stream complexity, high stream water temperatures, and impediments to fish passage:
- Historical stream management practices included removal of large wood from streams, sometimes to allow floating logs to the mills down stream and sometimes in the mistaken belief that removing large wood would create better conditions for salmon production. We have learned that large wood is actually an important part of the stream habitat needed for salmon production as it creates a variety of conditions that support both salmon spawning (spawning gravel) and rearing (stream pools). Habitat surveys and the Nehalem Data Synthesis project have allowed us to identify areas in the watershed that need more large wood.
- Salmon prefer low water temperatures. Coho salmon which were on the endangered species list during the late 90’s need cold water for spawning in the fall and also cold water during the summer for rearing. Historical logging and farming pratices removed stream side trees allowing direct sunlight to warm the stream waters. The stream habitat studies and the Nehalem Data Synthesis project have allowed us to identify those areas in the watershed most in need of additional trees to provide shade.
- Logging, farming, and rural development have created a extensive network of roads in the Lower Nehalem watershed. The combination of the road and streams produces a large number of road stream crossings. Many of these road stream crossings involve the use of culverts. Some of these culverts become barriers to fish passage. This results in steam segments that can not be accessed by migrating salmon and hence reducing the area available for spawning and rearing. Visits to road crossing coho streams resulted in the identification of 22 culverts that appeared to be barrriers to fish passage. Most had a limited impact on available habitat. The culverts at Jetty Creek, Roy Creek, and Neahakahnie Creek showed the greatest impact on available salmonid habitat. The Jetty Creek culvert was replaced by a bridge in 2008, and the Neahkahnie and Roy Creek culverts are on track toward replacement. Tide gates are used to keep high tides from flooding farm land around the Nehalem Estuary. These tide gates can also block access to potential salmon habitat.
These three watershed problems, lack of large woody debris, high stream temperatures and fish passage barriers, have been the focus of the State and Lower Nehalem Watershed Council efforts. Studies have also shown the existence of other water quality problems in the watershed.
- E-coli sometimes reaches high levels in streams and rivers. This e-coli can be a danger to human health through contact during recreational activities.
- Low water flows during the summer can contribute to high stream temperatures and smaller areas of water available for Coho salmon rearing. Summer water flows are reduced as farmers take water from the river for use with their crops and livestock.
- Excessive stream sediment can burry salmon eggs and reduce salmon productivity. Unfortunately we do not have standards for sediment, and as a result this problem has received less attention than it probably deserves. Timber owners, however, have been putting additional rock on their dirt roads to reduce the discharge of fine sediment into streams.