Case Study 8 North Fork Nooksack River In-channel Project Project Overview The North Fork Nooksack In-channel project was developed cooperatively between the USDA Forest Service and the Nooksack Salmon Enhancement Association (NSEA), with the objectives of (1) decreasing egg-to-fry loss of native chinook, coho, cutthroat, pink, sockeye, steelhead, and char due to redd scour and (2) decreasing frequency of dewatering of side-channels, which are areas containing valuable spawning and rearing habitat. The 3-mile project reach marks the uppermost extent of anadromous use and consistently sees a high amount of use by spawning North Fork Nooksack River salmon. The reach is also used extensively for stock enhancement in the Nooksack Chinook salmon recovery program. The North Fork In-channel Project was completed in two phases in the summers of 2003 and 2004. It consists of 36 logjams (9 small unballasted and 27 large ballasted structures) through the 3-mile reach (figure 1). The Lummi Indian Nation’s Natural Resources Department (LNR) has been working with the USDA Forest Service to monitor the habitat effects of the project, while NSEA has completed topographic surveys through the reach to help characterize the geomorphic response of the channel to the structures. We expect that differentiating the river response to the project from the natural range of conditions will take long-term monitoring. This report represents only the first year of post-construction monitoring. The project relies on the dynamic that exists between riparian forest, wood recruitment, and wood jams in the North Fork Nooksack. This project is the first stage in restoring a self-sustaining dynamic river morphology and habitat to a forested floodplain river. The following monitoring results only address the first stage of “river development succession,” hastening wood collection and bar development. Once the bars become more stable, vegetation colonization of bars can begin. Established vegetation North Fork Nooksack River In-channel Project is expected within 3 years, including effective vegetation filtering of floating wood during flood events. Finally, continued vegetation and wood collection will lead to periodical channel blockage and resultant shifting into overflow channels with a projected 25-percent increase in reconnected floodplain channels. Each of these developments takes time. This system averages a 4-year adjustment period from major storms due to limited stabilizing elements like large woody pieces. Six major events (greater than 10-year return interval) have occurred since 1989, and storms of this size are the trigger for the larger sediment pulses and wood recruitment (USDA Forest Service 1995). Since the storm of record for the North Fork Nooksack occurred in 2003, we project that it will be 2007 when the telling results and conclusions can be made. We expect that these changes in habitat- 3—89 Developing Monitoring Plans— Chapter 3 forming processes will lead to reduced scour of redds and more stable side-channel habitat. A basin-wide report on redd scour in the Nooksack Basin found redd scour to be greatest in main-stem and braided reaches, and it suggested using wood to stabilize bars and increase side channel habitat as a means of reducing redd scour and limiting the dewatering of side channels (Hyatt and Rabang 2003). Project Methods, Design, and Monitoring The basic design for monitoring the results of this multiyear structure- placement project was to compare fish habitat changes between the pre- and post-project conditions. First, we used a five-level hierarchical habitat classification system (based on modifications of the habitat classification system described by Hawkins et al.1993) to describe habitat in the reach. The first-level classification identified the channel types as main channel, braided channel, or side channel, while levels 2 through 4 classify the main geomorphic units (pools, riffles) of the channel. For level 2, the water is classified as fast or slow moving. Level 3 further separates these two classes as turbulent or nonturbulent fast water, and scour pool or dammed pool. Level 4 divides these groups further. For example, turbulent riffles can be classified as falls, cascades, rapids, riffle, or chute; and scour pools can be classified as eddy, lateral, midchannel, trench, convergence, or plunge. We classified bank conditions by resistance to channel migration, either bedrock, boulder, or armored. If the banks fell in none of those categories, we classified them by the riparian stand characteristics (Duck Creek Associates 2000). Second, for each habitat we measured unit, length, width, maximum and average depth, bank angle, vegetation overhang, undercut banks, length and width of available cover, and dominant/subdominant substrate were measured. We measured depth with a stadia rod and recorded it to North Fork Nooksack River In-channel Project the nearest 0.1 meter. To characterize the bank angle, we measured the distance from the toe of the bed to the water edge (measured horizontally along the water surface) and the depth of the water at the toe. For example, a perfectly flat (horizontal) bank would be 0 degrees and a vertical bank would be 90 degrees. Undercut banks would have bank angle values of greater than 90 degrees. We measured vegetation overhang with a stadia rod and included only vegetation within 300 millimeters (1 foot) of the water surface. We estimated each cover component based on length and average width, or (in the case of substrate) as a percentage of the entire habitat unit. 3—90 Case Study 8 Figure 1. General location of the North Fork Nooksack in-stream project. Third, we mapped large woody debris as logjams and key-sized pieces. Since the bankfull width of the channel was greater than 20 meters (65 feet), we defined a key-sized piece as greater than 9 cubic meters (11.7 cubic yards) in volume (Washington Forest Practices Board [WFPB] 1997). In this assessment, the “key-sized” designation does not indicate the size for a single piece of wood to be stable in the channel. Instead, it represents the size of wood being contributed by the approximately 500- year-old riparian stands that exist in two locations in the reach. For wood accumulations, we located each logjam and described any geomorphic or North Fork Nooksack River In-channel Project habitat effects. The geomorphic and habitat effects included the following: l split low flow: The logjam was actively splitting flow around or through it during low-flow conditions. l split bankfull flow: The logjam would be splitting flow when the stage was approaching bankfull. l channel deflection: The logjam was actively turning or deflecting the channel at low flow. 3—91 Developing Monitoring Plans— Chapter 3 l sediment storage: The evidence showed that the channel slowed velocity and deposited sediment adjacent to the logjam. l pool formation: The evidence showed scour adjacent to the structure. l cover: The logjam was providing hiding cover for juveniles during low-flow conditions. We estimated the stability of the logjam from indicators such as persistent vegetation, effects on the channel, and persistence of the structure on aerial photos. We independently identified and described any key-sized pieces associated with the logjams. The main limitation of the mapping was that smaller pieces of drift were not characterized. Therefore, we could not characterize the total volume of wood in the reach. Monitoring Results and Interpretation Project Reach Changes Although the reach has an average slope of 0.008, this slope varies considerably within the reach from 0.005 to 0.02 (Indrebo 1998; GeoEngineers, Inc. 2001). The active channel width varies from approximately 50 feet, where it is confined between bedrock walls, to more than 650 feet, where it is often braided or has vegetated islands splitting the channel. The channel is dominated by riffle-pool morphology, with substrate, vegetation, and woody debris forming the dominant roughness elements, depending on the degree of channel confinement. We estimated the bankfull and 2-year return intervals for the discharge in the reach at 4,400 cubic feet per second for the bankfull interval and 6,000 cubic feet per second for the 2-year return (Indrebo 1998, GeoEngineers, Inc. 2001). Since construction, the project has been subjected to several flows greater than bankfull stage, which occurred in mid-October 2003. North Fork Nooksack River In-channel Project Although a U.S. Department of the Interior U.S. Geologic Survey gauge at road marker 63 and within the project reach was not reporting, the flow was estimated to have been approximately 14,000 cubic feet per second, with a secondary peak 5 days later of over 12,000 cubic feet per second (Gary Ketcheson, U.S. Forest Service, personal communication, May 2004). These were the largest floods since the gauge began operation in 1937, and both of these peaks were estimated to have been greater than the 100-year flood level. The flood appears to have had only a modest impact on the channel planform, largely in the unconfined sections of the project reach. In these areas, meander bends have migrated slightly downvalley, or sediment deposition has led to braiding of the channel. In other sections of the reach, the channel appears to have incised and narrowed during the flood. 3—92 Case Study 8 Fish Habitat-forming Processes—Sediment Production and Transport In the project reach, sediment is supplied from tributaries within the reach and as bedload transported from upstream. A comparison of aerial photos, conducted by GeoEngineers, Inc. (2001), indicates the occurrence of frequent fluctuations in channel width—episodes of accelerated lateral migration, bank erosion and channel avulsion (the removal of a piece of land from one property onto another as a result of a shift in the course of a boundary stream). The North Fork Watershed Analysis (USDA Forest Service 1995) found a relationship between channel widening and flood occurrence in the response (lower gradient and unconfined) reaches of the North Fork Nooksack.