Bayha and Wright Islands are part of the U.S. Fish and Wildlife Service (USFWS) Snake River Islands Unit of the Deer Flat National Wildlife Refuge and are in the Snake River approximately 2.5 miles downstream of Walter’s Ferry in southwestern Idaho.
The Bayha Island Research Project was designed to narrow and deepen a section of the Snake River channel by creating approximately 10 acres of wetlands (also called floodplain) adjacent to the islands, thereby increasing water velocity and decreasing heating by decreasing the surface area of the river during low summer flows.
The floodplain was also planted with native trees and shrubs such as willows, rabbitbrush, currants, native grasses and sedges to prevent erosion, provide shade, and improve wetland habitat.
An illustration of how this type of island project can be used to narrow the river channel is shown below.
Construction consisted of dredging the river’s channel between Bayha and Wright islands and the south bank of the river, and narrowing the channel by creating additional wetlands around the islands. Construction was completed in 2016, but work will continue with additional revegetation, irrigation until plants are established and monitoring of plant and river conditions.
In the illustration below, the orange and red indicate areas that were filled, while the blue is the river channel that was deepened. We sourced the estimated 80,000 cubic yards of fill material from the dredging operation and a nearby gravel deposit located on a neighboring landowner’s property. This kept approximately 4,000 dump truck trips off public roads and benefited the landowner by improving a field and pond.
Conceptual Grading Analysis
Idaho Power and The Freshwater Trust will use information gained from the research project to further develop a comprehensive strategy for addressing water quality issues throughout the Mid-Snake.