research project details
Project Title: The Impacts of Commercial Jet Boating on Salmon and
Eagle Habitat in the Chilkat Bald Eagle Preserve, Alaska
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 include:
- Quantification of the wake characteristics (amplitude, frequency, number of waves) of boats operating in the areas of interest. These characteristics will be very strong functions of boat parameters such as the length, power, etc., and operating parameters, such as speed and distance from shoreline. Determination of this functional dependence is viewed as highly significant.
- Quantification of near-bank turbidity and mobilization in order to correlate wake height with the onset of motion of bank materials.
- Quantification of the near-bed disturbance underneath passing boats. This disturbance, which may be sufficient to resuspend bottom materials, also will be a function of boat and operating parameters.
- Determination, through analysis, of the relative importance of these boat-related mechanisms to erosional processes, as compared to natural mechanisms such as wind-waves, currents, and floods.
Summary:
The CBEP, located near Haines , Alaska , was created in 1982. Consisting of 48,000 acres, the Preserve provides habitat for the world's largest concentration of bald eagles, who are drawn to the location by a combination of a late fall / early winter salmon run and the flow of relatively warm water in the Chilkat River.
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.
A team from PSU conducted a field study in the summer of 2002, with the goal of measuring the characteristics of the boat wakes, as well as the characteristics of the ambient streamflow.
Methodologies:
Numerous methodologies will be used in order to achieve the project objectives:
- Wakes will be measured with capacitance wave-gages in order to determine the variation of water surface elevation with time. Controlled experiments will be conducted, allowing for highly accurate measurements of boat speed and distance from sailing line to measurement point. Alternatively, radar technology can be used in order to measure the speed of passing 'non-participating' boats.
- Turbidity measurements will be made with a Downing and Associates Optical Backscatter Sensor.
- Near-bed hydraulic disturbances will be measured with a SonTek Acoustic Doppler Velocimeter.
- Extensive photographic documentation of bank areas will be conducted to assist in longer-term monitoring efforts.
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