WEST WEAVER CREEK Assessment and Action Planning
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WEST WEAVER CREEK Assessment and Action Planning Prepared for August 2012 Trinity County Resource Conservation District WEST WEAVER CREEK Assessment and Action Planning Prepared for August 2012 Trinity County Resource Conservation District 2600 Capitol Avenue Suite 200 Sacramento, CA 95816 916.564.4500 www.pwa-ltd.com Los Angeles Oakland Olympia Petaluma Portland San Francisco San Diego Seattle Tampa Woodland Hills D211670.00 WEST WEAVER CREEK ASSESSMENT AND ACTION PLANNING TABLE OF CONTENTS Page 1 Introduction 1 1.1 Overview of the Assessment 1 1.2 Goals 2 1.3 Objectives 2 1.4 Conclusions 2 2 Setting 4 2.1 Geography and Land Ownership/Management 4 2.2 Infrastructure 5 2.3 Topography and Land Cover 5 2.4 Geology, Soils and Hillslope Processes 6 2.5 Hydrology 7 2.5.1 Climate 7 2.5.2 Basin characteristics 7 2.5.3 Flows 7 3 Watershed History 9 3.1 Land Use Practices 9 3.2 Recent Fire History 9 3.3 Past Stream Assessments 10 3.3.1 West Weaver Creek Fish Habitat Assessment (1990 Ebasco) 10 3.3.2 Weaverville Watershed Analysis (2004 USFS) 10 3.4 Past Stream Restoration Efforts 11 4 Existing Channel Conditions 12 4.1 Water Quality 12 4.2 Stream Classification 12 4.3 Riparian Vegetation 13 4.4 Fish Ecology and Habitat 13 5 Field Reconnaissance and Assessment 15 5.1 Field Reconnaissance 15 5.1.1 Initial Reconnaissance 15 5.1.2 Detailed Reconnaissance 16 5.2 Analysis 19 5.2.1 Examination of Profile 19 5.2.2 Analysis of Cross Sections 19 5.2.3 Analysis of Culvert Hydraulics for Fish Passage 22 5.3 Summary of Field Assessment, Modeling and Analysis 23 5.3.1 Top 5 Priority Issues 24 5.3.1.1 Issue 1 – Exposed bedrock and shallow in-channel substrate depth in the focus reach 24 5.3.1.2 Issue 2 – Lack of lateral channel migration in the focus reach 24 West Weaver Creek i ESA PWA / D211670.00 Assessment and Action Planning August 2012 WEST WEAVER CREEK ASSESSMENT AND ACTION PLANNING 5.3.1.3 Issue 3 – Lack of floodplain connectivity in the focus reach 25 5.3.1.4 Issue 4 – Fish passage at Highway 299 Culvert (RM 2.3) 25 5.3.1.5 Issue 5 – Fine sediment from Grub Gulch (RM 1.8) 25 6 Opportunities and Constraints 26 7 Recommended Actions 28 8 References 30 List Of Tables Table 2.1 Estimated return interval discharges at West Weaver Creek basin outlet. 8 Table 5.1 Return interval discharges at the focus reach for the methods used 20 Table 5.2 Velocity depth results from the hydraulic analysis for XS1-4 20 Table 5.3 Critical shear stress required to entrain certain particle sizes 21 Table 5.4 Results of open channel shear stress calculations for XS1 through XS4 21 Table 5.5 Comparison of CDFG passage criteria to results of hydraulic analysis for fish passage through the Highway 299 culvert 23 List Of Figures Figure 2.1 West Weaver Creek Setting Figure 2.2 West Weaver Creek Geography Figure 2.3 West Weaver Creek Land Ownership/Management and Infrastructure Figure 2.4 West Weaver Creek Valley Profile: Headwaters to the Confluence Figure 2.5 West Weaver Creek Topography and Land Cover Figure 2.6 West Weaver Creek Geology Figure 3.1 West Weaver Creek Recent Fire History Figure 3.2 Affects of the Oregon (2001) and Junction (2006) Fires: Aerial Photo Time Series Figure 5.1 Initial Field Reconnaissance Notes and Photos Figure 5.2 Highway 299 Box Culvert and Fish Passage Baffles Figure 5.3 Surveyed Longitudinal Stream Profile of Focus Reach Figure 5.4 Detailed Field Reconnaissance of Focus Reach Figure 5.5a West Weaver Creek Hydraulic Analysis Focus Reach: Cross Section 1 Figure 5.5b West Weaver Creek Hydraulic Analysis Focus Reach: Cross Section 2 Figure 5.5c West Weaver Creek Hydraulic Analysis Focus Reach: Cross Section 3 Figure 5.5d West Weaver Creek Hydraulic Analysis Focus Reach: Cross Section 4 Figure 5.6 Highway 299 Box Culvert Baffles Hydraulic Analysis Locations Figure 7.1 Conceptual Design Alternatives for the Focus Reach West Weaver Creek ii ESA PWA / D211670.00 Assessment and Action Planning August 2012 WEST WEAVER CREEK ASSESSMENT AND ACTION PLANNING 1 INTRODUCTION 1.1 Overview of the Assessment Rivers are comprised of their contributing tributaries and upstream watersheds. These tributaries contribute more than water—they provide important contributions of sediment, organic material, and also serve as habitat for resident and anadromous aquatic species. The tributaries of the Trinity River, downstream of Lewiston Dam, are perhaps even more important than in other basins, given the exclusion of anadromous habitat in the river’s watershed upstream of the dams. These tributary watersheds may also contribute to fine sediment loading of the river and habitat within the tributary streams themselves. The Trinity River Restoration Program includes the Watershed Restoration Program and Watershed Coordinator Program to assess, plan and implement tributary watershed restoration actions for an improved Trinity River. These watershed restoration activities require a combination of actions that: 1) (re)establish natural physical processes that create and maintain high-quality aquatic habitat, and 2) improve spawning and rearing conditions downstream of the dams that best compensate for lost habitat upstream. Over the past century West Weaver Creek, a tributary and contributing watershed of the Trinity River, has experienced a number of land use stressors including hydraulic mining, fire, timber harvest, road construction, and urbanization. Fortunately, West Weaver Creek exhibits strong potential for improved spawning and rearing conditions given the appropriate rehabilitation effort. This report provides: • A general overview of the watershed’s geography, land use and ownership, hydrologic and geomorphic setting. • The history of the watershed as it concerns the existing physical and ecologic conditions of the channel. • A review of initial field reconnaissance efforts and description of observations sufficient to focus more-detailed field surveys. • A review of more-detailed surveys and field observations • A summary of hydrologic and hydraulic analyses for a focused reach of creek, including fish passage at Highway 299. • A summary of key issues and recommendations for next steps, including provision of potential restoration design concepts. The work completed to assess West Weaver Creek and prepare this report focused on providing information and recommendations to guide restoration funding to the most appropriate locations and issues, relative to improving aquatic habitat for important fish species of concern. This work also sought to recommend a specific set of prioritized actions to help apply restoration funding in West Weaver Creek 1 ESA PWA / D211670.00 Assessment and Action Planning August 2012 WEST WEAVER CREEK ASSESSMENT AND ACTION PLANNING a manner that addresses key stressors and reinvigorates the physical and ecological processes that create and maintain desirable habitat conditions in the West Weaver Creek. 1.2 Goals The Trinity River receives fine sediment from its watersheds at levels above that which is considered acceptable for the protection of the aquatic ecosystem (US EPA, 2001). The Trinity River Watershed Council, the Trinity County Resource Conservation District, and the Trinity River Restoration Protection, and other natural resource management agencies at the state and federal level all want to reduce the fine sediment entering the mainstem river from the West Weaver Creek watershed. Reducing West Weaver Creek’s fine sediment yield to the Trinity River is an important project goal. As a tributary to the Trinity River, West Weaver Creek provides valuable spawning and rearing habitat for endangered salmonids in the Trinity River basin. A number of anthropogenic stressors (mining, timber harvest, urbanization, water diversion) in the watershed may affect the quality of salmonid habitat. Another project goal is to improve quantity, quality and access to salmonid habitat in this tributary to the Trinity River. 1.3 Objectives The objectives of this assessment focused research and evaluation first at a broad, regional scale, then sequentially refined the focus downward until issues related to salmonid habitat and sediment yield were identified at a local, reach scale. Issues that span the entire basin, and/or are at a broad, landscape-level, such as forest road erosion or background sediment yield from timber harvest, were not considered in this assessment. For the purposes of this assessment, watershed stressors/habitat issues were defined at the discrete and/or reach-scale and also present an opportunity for execution of manageable rehabilitation efforts to address the goals of the project. The specific objectives of the assessment were: • Understand the general setting of watershed • Review historical conditions (primarily the disturbance history), previous studies and past rehabilitation efforts • Conduct a field reconnaissance effort to assess existing watershed channel/floodplain conditions as they pertain to salmonid habitat and sediment yield • Identify and prioritize issues related to salmonid habitat and sediment yield • Recommend actions to address these issues 1.4 Conclusions • The reach of West Weaver Creek that deserves immediate attention, in terms of focused rehabilitation effort, begins just upstream of Grub Gulch (RM 1.8) and ends just downstream of Highway 299 (RM 2.3). West Weaver Creek 2 ESA PWA / D211670.00 Assessment and Action Planning August 2012 WEST WEAVER CREEK ASSESSMENT AND ACTION PLANNING • Future rehabilitation efforts should develop a design that includes reconfiguration of the channel’s width, slope, and its ability to connect with the adjacent floodplain. - This includes increasing in-channel substrate in areas currently scoured to bedrock, and the expansion of the channel and floodplain width in key locations sufficient to support hydraulic conditions that will maintain desirable riffle-pool channel morphology. - The design process should consider sorting and grading of the floodplain to create beneficial conditions for revegetation and long-term geomorphic processes (such as sediment sorting and deposition on the floodplain; and in the long term allow for channel avulsion).