Title: Supplemental Environmental Assessment & Finding of No Significant Impact - Ponca Backwater Shallow Water Habitat Maintenance, Dixon County, Nebraska
Summary: The original project, consisting of 29 acres of backwater habitat, was constructed in 2004 to function as shallow water habitat with the intent to benefit the federally endangered pallid sturgeon and other native fish and wildlife species. The 2011 Missouri River flood washed out land that separated the upstream and downstream backwaters, causing a portion of the upstream backwater and entire downstream backwater to function as a flow through chute. This caused sedimentation in the portions of the backwaters that were flowing, making them shallower than desired and filling in the deep-water overwintering fish holes. The flood also caused approximately two feet of bed degradation in the main channel of the river, which lowered the water surface elevation for a given flow by approximately two feet, causing the water in the constructed backwaters to be two feet shallower than designed.
Proposed repairs are needed to return the site to its original design and functionality and will include excavation and discharge of accreted Missouri River sediments, placement of earthen fill between the two backwater areas, and construction of rock revetment with a covering of fieldstone, topsoil and native grass seed.
Geographic Scope: Along the right descending bank of the Missouri River near river mile 754 on Nebraska Game and Parks land within Ponca State Park boundaries in Dixon County, Nebraska
Impacts: None
Decision/Date: Made following close of public comment period.