research project details
Project Title: Chilkat River Project (Year 2)
Investigator(s): David Hill
Sponsor: Alaska Department of Fish and Game
Environmental Problem Addressed:
Degradation of Chilkat River Ecosystem
Research Project Objectives:
Investigate the effects of large jet boat operations on the banks and bed of the Chilkat River , in the Alaska Chilkat Bald Eagle Preserve (CBEP). This research is seeking to determine if large jet boat operations are causing accelerated bank erosion and related impacts to spawning and rearing habitat on the Chilkat River near the Kelsall River confluence. The purpose of this project is to determine if commercial jet boat tours are causing adverse impacts to fish habitat in the Alaska CBEP. This study will assist with management decisions being made to adequately protect the Preserve resources.
The specific objectives of Year 2 include:
- Detailed quantification of the flow and turbidity distributions near the banks, in the absence of boating activity. Year 1 made only limited measurements of these quantities; Year 1 emphasis was on wake heights. Goal is to gain a thorough understanding of baseline river conditions of the habitat for rearing salmonids.
- Detailed quantification of the flow and turbidity measurements near the banks, in the presence of boating activity. The goal is to expand the rough comparative estimates of boat-related and flow-related bank impacts made in Year 1. the near-bank disturbances will be functions of the height of the wakes striking the banks.
- Laboratory study of the response of hatchling fish to various fluid mechanical parameters and turbidity. A preliminary review of the pertinent literature reveals that several past studies similar in nature have been conducted. Unfortunately, many of these studies have been poorly designed from a fluid mechanics point of view. This study aims to research the effect of multiple exposures to lower levels of shear more realistically represent the current conditions.
Summary: 
Recently, the Alaska Department of Fish & Game (ADFG) articulated concern that levels of commercial jet-boat traffic have risen to heights neither anticipated nor adequately addressed by the original preserve management plan. The specific concerns are that boat-generated wakes are accelerating erosion of the river's banks (see figure) and that the boats, which can operate in extremely shallow water, may be 'scouring' the river bottom, which is prime salmon spawning habitat.
Methodologies: Numerous methodologies will be used in order to achieve the project objectives for Year 2:
- The near-bank velocity and turbidity profiles will be measured with an array of acoustic Doppler velocimeters and optical backscatter sensors.
- The laboratory studies will be conducted with a variety of facilities. In order to assess the effects of shear stress, a rotating Couette flow will be used. Comprised of two concentric cylinders, one fixed and one rotating, this arrangement generates a flow field characterized by constant stress. By adjusting the rotational rate of the free cylinder, the level of shear stress can be carefully controlled.