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Draft Channel Modifications White Paper

Category: Habitat - Habitat Conservation Plans

Date Published: December 28, 2007

Number of Pages: 226

Author(s): Herrera Environmental Consultants, Inc.


In 2006 and 2007, WDFW contracted with Anchor Environmental, Herrera Environmental Consultants, Jones & Stokes Associates, and R2 Resource Consultants to develop a series of “white papers” documenting the state of the science on a range of topics related to HPAs. The original white papers were peer-reviewed by a panel of experts outside of WDFW.

In developing the white papers, the consultants were working under specific time, scope, and cost constraints established by WDFW. These constraints were designed to further WDFW's specific goal of building a scientific foundation for a Habitat Conservation Plan for hydraulic projects that receive HPAs.

The white papers provide a solid scientific foundation upon which to build conservation measures for avoiding potential impacts, but they are not an exhaustive review of every potential impact of hydraulic projects. Rather, they reflect WDFW’s goal of establishing a solid scientific foundation for the HCP with limited time and financial resources.

Despite these constraints, WDFW is confident that a large proportion of the current scientific literature has been incorporated into the white papers. As WDFW continues to develop the Habitat Conservation Plan, we will also continue to assess new science, fill data gaps, and listen to the advice of scientists and hydraulic project construction specialists.


The Revised Code of Washington (RCW) directs the Washington Department of Fish and Wildlife (WDFW) to “preserve, protect, perpetuate, and manage” the fish and wildlife species of the state as its paramount responsibility (RCW 77.04.012). Under RCW 77.55, any construction or work that uses, diverts, obstructs, or changes the natural bed or flow of state waters requires a Hydraulic Project Approval (HPA) issued by WDFW. The purpose of the HPA program is to ensure that hydraulic projects are completed in a manner that prevents damage to public fish and shellfish resources and their habitats. To ensure that the HPA program complies with the Endangered Species Act (ESA), WDFW is developing a programmatic multispecies Habitat Conservation Plan (HCP) to obtain an Incidental Take Permit (ITP) from the U.S. Fish and Wildlife Service (USFWS) and the National Oceanic and Atmospheric Administration (NOAA) Fisheries Service (also known as NOAA Fisheries), in accordance with Section 10 of the ESA. For WDFW, the objective is to ensure that activities conducted under an HPA avoid and/or minimize the incidental take of aquatic species potentially considered for coverage under the HCP (referred to in this white paper as “HCP species”).

The HCP will address the impacts, potential for take, and mitigation measures for effects on HCP species from hydraulic projects that require HPAs. WDFW’s intent is to build the scientific foundation for the effort to prepare an HCP for hydraulic projects that receive HPAs. To accomplish this, WDFW is compiling the best available scientific information related to the impacts, potential for incidental “take” of species that may be covered in the HCP (as defined in the ESA; see Section 9 of this white paper for a definition of “take”), and possible management directives and mitigation measures to avoid and/or minimize potential take to the maximum extent practicable. As the HPA authority covers all waters of the state, this white paper considers hydraulic project impacts in both freshwater and marine environments.

This white paper is one of a suite of white papers prepared to establish the scientific basis for the HCP and to assist WDFW decision-making on what specific HPA activities should be covered by the HCP. This particular white paper compiles and synthesizes existing scientific information on channel modification activities, which in this white paper analysis include dredging, gravel mining and bar scalping, sediment capping, and channel creation and alignment.

The objectives of this white paper are to:

  • Compile and synthesize the best available scientific information related to the potential human impacts on HCP species, their habitats, and associated ecological processes resulting from the construction, maintenance, repair, replacement, modification, operation, and removal (hereafter collectively referred to as construction and maintenance) of dredging operations, gravel mining and bar scalping, sediment caps, and channel creation and alignment activities.
  • Use this scientific information to estimate the circumstances, mechanisms, and risks of incidental take potentially or likely to result from channel modification activities as defined herein.
  • Identify appropriate and practicable measures, including policy directives, conservation measures, and best management practices (BMPs) to avoid, minimize, or mitigate the risk of incidental take of HCP species.

The literature review conducted for this white paper identified seven impact mechanisms that could potentially affect HCP species. These mechanisms of impact are both direct and indirect and can have temporary, short-term effects or permanent, long-term effects. The impact mechanisms analyzed in this white paper are:

  • Construction and maintenance activities
  • Dredging equipment operation
  • Hydraulic and geomorphic modifications
  • Riparian vegetation modifications
  • Aquatic vegetation modifications
  • Water quality modifications
  • Ecosystem fragmentation

This white paper includes a discussion of the potential direct and indirect impacts on the 52 HCP species and their habitats due to exposure to the identified impact mechanisms. Following this discussion, an evaluation of potential for take of the 52 HCP species is included based on a separate analysis conducted using exposure-response matrices for each of the HCP species. This white paper also reviews data gaps and, where there is sufficient information, estimates the risk of take. In addition, habitat protection, conservation, mitigation, and management strategies that could avoid, minimize, or mitigate the identified potential impacts are provided. Key elements of the white paper are to:

  • Identify the distribution of the 52 HCP species (i.e., whether they use fresh water, marine water, or both) and their habitat requirements.
  • Identify the risk of “take” associated with each of these impact mechanisms based on the distribution information.
  • Identify cumulative impacts.
  • Identify data gaps.
  • Identify habitat protection, conservation, and mitigation strategies.