The world’s rivers and streams are adjusting to changes in climate. In Washington State, stream channels are becoming more dynamic – especially in the vicinity of gravel-bed rivers. Federal, state, tribal and private roads are increasingly compromised or destroyed due to progressively more dynamic channel processes. A river’s bedload (sediment transported along the channel bed) drives how rivers move into – or away from – road infrastructure. In order to design durable roads and bridges, we need high quality information on how the natural material in the river system will move and deposit in the vicinity of road infrastructure. Widely available methods for assessing channel dynamics and hazards are based on sand-bed rivers, like the Mississippi River, that do not apply to gravel-bed rivers found throughout the United States. We need a gravel-bed river assessment tool that accounts for changes in gravel-bed rivers from glacial melt and extreme flooding associated with projected future climate change. In this pilot, WSDOT proposes to develop practical guidance and methods for assessing bedload transport in gravel-bed rivers for more resilient road infrastructure. This guidance will inform engineering design, hazard assessment, and maintenance strategies of roads along or near gravel-bed rivers. Other federal and state agencies support the pilot, and are willing to assist in the development and review process. WSDOT anticipates that US Forest Service, US Fish and Wildlife Service, Oregon DOT, Caltrans and other public works agencies will use the gravel-bed assessment tool developed by this pilot project.

This pilot will consist of three parts: 1. A technical workshop to define the framework, goals, and criteria for developing the guidance and case studies. 2. Data collection and case study development. 3. The guidance write-up and finalization

Scope of Work: WSDOT will bring together with experts and stakeholders in a one-day technical workshop to establish the assumptions, key resources, goals and identify the data gaps. This will assist WSDOT in directing the data collection and other work of the consultants and staff within an established framework. WSDOT will test the sediment transport modeling capabilities of the Sedimentation and River Hydraulics – Two-Dimensional model (SRH-2D), now the preferred hydraulic modeling software by FHWA, and compare the results obtained from current FHWA Guidance HEC-18. The pilot study will also consider future extreme weather conditions using the methods described in HEC-17. The pilot will closely examine the state-of-art technology for collecting direct and indirect measurements of bedload (e.g., passive and active hydroacoustic, Acoustic Doppler Profiler (ADP), Apparent Bedload Velocity (ABV), photosieving, accelerometers, Passive Integrated Transponder (PIT) tags, remote sensing and GIS). WSDOT’s hydraulics staff have experienced many challenges in collecting physical bedload samples: it is often dangerous and untenable. Advancements in data collection techniques offer opportunities for indirect measurement of bedload while ensuring safety of DOT staff and contractors. These data could greatly improve the calibration – and therefore the results – of sediment transport models within acceptable limits of accuracy. Physical sampling of bedload (for calibrating sediment transport models) will be compared to data obtained from modern tools in data collection in three case studies. The outcomes will be applied towards guidance development. The goal is to identify data collection techniques that refine inputs into sediment transport models within acceptable limits of accuracy when field-based site calibration is unsafe or untenable. The pilot will conduct three case studies in order to develop the guidance and test methods with a focus on: • Stream Simulation culvert design for fish passage and geomorphic stability, particularly in dynamic settings such as alluvial fans and transitions of channel slope or confinement. • Design criteria for bridge and roadway projects at risk from channel migration and spatially-extensive bed scour or gravel accumulation. • Design of bank stabilization projects in a manner that maintains integrity of habitat and adjacent streambanks. Maintenance strategies for DOT infrastructure in rivers and streams, such as reconfiguring culverts on small creeks to prevent blockage from heavy aggradation that requires annual dredging. Following the completion of the three case studies, WSDOT will prepare the guidance document. This final stage will include a third party review by independent experts, as well as review by partners and stakeholders who have been engaged in earlier stages of the pilot. The final product of the pilot study will be the publication of WSDOT’s guidance and methods. These will be applicable to state DOTs and other highway asset managers across the nation wherever gravel-bed rivers are found. WSDOT will be the lead agency for the pilot. Partners currently include: USFWS (Region 1), Oregon DOT, Caltrans, USFS. We remain open to acquiring additional partners to strengthen the effectiveness of the pilot. Without pool funding, WSDOT would not be able to lead or participate in this work. WSDOT’s Hydrology Program provides direct technical support to funded projects. Project budgets do not have funds for experimental techniques. While WSDOT has a research program, it’s funding is very limited. External funds are essential for the success of this pilot project.

Participants are requested to contribute a minimum of $25,000 per year for 3 years.