200717800 - Monitoring fine sediment delivery in the Entiat subbasin
Sponsor: US Forest Service (USFS) - Pacific Northwest Research Station
Budgets: FY07: $265,570 | FY08: $145,830 | FY09: $154,010
Short description: Develop and test improved protocols for monitoring fine sediment in salmonid habitat.
Final Council recommendation (Nov 2006)
Funding category: Expense
Recommended budgets: FY07: $0 | FY08: $0 | FY09: $0
ISRP final recommendation: Fundable (Qualified)
The ISRP’s qualification for this “fundable” recommendation stems from the need for this study to examine the relationship between particle size distributions of deposited and suspended sediment in order to verify their assumption that suspended sediment provides a good surrogate measure for sediment levels in streambed gravel. There is additional discussion of this point below. Addition of this component would make this a very strong proposal, and this research would be relevant systemwide. Technical and scientific background: This proposal does a fairly thorough job of discussing the background of this issue. The importance of sediment to the quality and productivity of freshwater habitat is generally appreciated, so this topic is one of considerable importance to restoration and salmon recovery efforts. However, the proposal makes a major, the ISRP believes, unsupported assumption that suspended sediment levels are a good indication of levels of sediment deposited on the streambed. The relationship between levels of suspended sediment and fine sediment deposited in streambed gravel or in pools has not been well established. In fact, there are some studies that suggest that the two are not very closely associated. The Zimmerman and Lapointe study cited in the proposal apparently found a relationship between suspended sediment and infiltration of fine sediment into gravel baskets. However, there was no mention of whether or not the particle size distributions of the suspended sediment and that captured in the basket samplers were similar. It is possible that this relationship could have been caused by both suspended sediment and bedload being mobilized by the elevated flows, with the bedload movement being the process responsible for the deposition. The ISRP believes there are several studies that have examined the correspondence between particle size distribution of suspended sediment and fine sediments in streambed gravel and found little overlap. The suspended material is typically extremely fine, often dominated by clay-sized particles, whereas the fine sediment in the gravel was dominated by sand, a size fraction comprising a very minor component of the suspended load. This criticism is not intended to imply that this project is not worthwhile. On the contrary, a better understanding of suspended sediment dynamics at a watershed scale would be very useful. But to make the linkage to potential biological impacts, a characterization of the particle size distribution of streambed fines and suspended sediment should be included in the study. The proposal indicates that some streambed sampling is already ongoing in the Entiat as part of another project. Expansion of this program to cover a wider array of channel types and inclusion of particle-size distribution analysis on a subset of suspended sediment samples (those with the highest concentrations) would address this question. Were this comparison done across the range of channel types to be examined in this study, it might be possible to delineate where in the watershed suspended sediment levels are a good index of deposited sediment and where they are not. This understanding also would help to guide restoration efforts as particle size distribution varies among sediment sources (e.g., road surface erosion tends to produce very fine material, bank erosion and mass failures a wide range of particle sizes). Rationale and significance to subbasin plans and regional programs: This project does address an issue deemed important to salmon recovery in the Entiat Subbasin Plan. Fine sediment also is identified as an important issue in many other subbasin plans in the Columbia Basin. Relationships to other projects: There are ties with ongoing USFS projects as well as BPA funded RME projects in nearby subbasins (e.g., Wenatchee). The relationship of this effort to the objectives of the PNAMP process also is described. Objectives: The objective section should better reflect the actual technical objectives of the study. The objective presented simply repeats the subbasin plan goal of reducing fine sediment levels in stream gravel to <12%. The work elements described in the proposal do not directly address this objective. In fact, sampling of stream gravels is not included, so this study will not provide information indicating whether or not progress is being made against this objective. The objectives should be expanded and made explicit to the work elements included in the study. For example, a primary objective appears to be a characterization of the relationship between flow and suspended sediment concentration and load in streams of varying size, land uses and disturbance history. Tasks (work elements) and methods: Work elements are clearly stated and outlined with summary of methods to be used. Monitoring and evaluation: This entire project is a RME effort. It is generally very strong from a technical perspective. The monitoring and evaluation protocols developed should be useful for other projects. Facilities, equipment, and personnel: Personnel are well qualified. No justification is provided for equipment costs for this project, which are high (approx. $125,000). Information transfer: Information transfer appears adequate with dissemination through scientific channels plus the data will be made available on the USFS website. Benefits to focal and non-focal species: A better understanding of suspended sediment dynamics, especially the watershed-scale approach being proposed for this study, will provide information relevant for efforts to restore populations of the fishes listed as primary and secondary focal species. An improved understanding of sediment is likely to have large benefit, assuming the relationship between suspended sediment measurements and actual gravel sediment is real. Adverse effects to non-focal species are not likely.
State/province recommendation: MS: Do Not Fund
Review group: MSRT
Recommended budgets: FY07: (n/a) | FY08: (n/a) | FY09: (n/a)
Comment: The MSRT questions BPA responsibility for this project. There is currently an MOU between USFS and BPA that covers cost sharing where there is shared responsibility for mitigation. The MSRT did not find a good fit in the Council's research plan for this project. Is this project coordinated with the CSMEP and PNAMP sampling protocols efforts? The sponsors propose to develop protocols, but then propose a continuous study with no end determined.