Much of the Central Platte NRD has long been plagued by floods. On the average, there’s a flood every year in some area of the District, with major floods occurring every six to eight years. The land area within the District is unusual in the fact that most of the tributaries of the Platte River run almost parallel to the Platte itself. Consequently, the tributaries span many miles of the flat terrace or bottomlands adjacent to the Platte before emptying into the river.
In the central and western ends of the District, most of the tributaries originate in the uplands where flood control structure sites are plentiful, but then drop off into the flat terrace or bottomlands and meander for many miles before reaching the Platte River. Many of the District’s other streams, such as Silver Creek, Warm Slough, and the North Branch, originate in the flat terraces or bottomlands where there are no sites for flood control structures. Even Prairie Creek has no flood control structure sites except in its extreme upper reaches.
The Wood River has approximately 173 miles of channel meandering through the fertile Platte River Valley. There are numerous flood control structure sites in its upper reaches. However, in the flood of June 1967 on the Wood River, most of the rain contributing to the flooding in the Grand Island area fell east of Kearney where there are few flood control structures sites. Although flood control structures are or could be, of great benefit to this area, total protection cannot be achieved without some form of channel rectification. The Board has adopted, as a general policy, the design and construction of flood control measures on a watershed basis.
The NRD has developed over 30 flood control structures. The plans for these structures have been designed to provide for orderly development of flood control and other related resources activities in watersheds, with each watershed plan encompassing a number of individual project plans in the total watershed development.
PROJECTS UNDER CONSTRUCTION AND PLANNING
Flood Planning Grants
In April 2020, CPNRD was selected to receive Watershed & Flood Prevention Operations Program (WFPO) grants from NRCS to identify what is needed to address flooding within the Spring and Buffalo Creek Watershed ($625,000) and the Lower Wood River Watershed ($725,000) and to design specific watershed plans. The two-year grants pay 100% of costs to complete an Environmental Assessment (EA) for each watershed. JEO and EA Consultants were hired to develop the EA for the Lower Wood River Watershed Work Plan to include portions of Buffalo, Hall and Merrick counties. A virtual public meeting was hosted by JEO on August 18, 2020. HDR Engineering was hired to develop the EA for the Buffalo Creek/Spring Creek Watershed Work Plan in Dawson County.
In June 2020, CPNRD received funding to complete a WFPO-EA Plan for Elm and Turkey Creek Watershed ($742,000). The Elm and Turkey Creek Watershed project area covers 106,185 acres in Dawson and Buffalo counties. Allen Gehring, NRCS state engineer, is the Government Representative for the projects.
HAZARD MITIGATION PLAN
In 2008, FEMA awarded CPNRD a grant to develop a multi-jurisdictional All-Hazard Mitigation Plan; enabling communities to take action & reduce threats from natural disasters. Public input from officials and landowners were a key component of the process. Regional meetings were held to obtain input in the initial stages. Potential hazards affecting the area, individual communities identified, critical facilities located, and potential mitigation actions/projects were listed. Projects considered are flood and drainage system improvements, backup generators for critical facilities, alert sirens, weather radios, tornado shelters/safe rooms, tree inventory, and programs to reduce electrical outages. CPNRD sponsored the initial plan in 2010 and the 2017 update (updates required every five years). In October 2020, CPNRD signed an agreement with NEMA to update the Plan.
PLATTE VALLEY DRAINAGE
An agreement to address long-standing drainage at the Platte Valley Industrial Park and the surrounding area in Grand Island was approved by the Grand Island City Council and Hall County Board of Commissioners in October 2020. CPNRD’s board will likely take action on the agreement at their November meeting.
In 2016, JEO Consulting was hired for $39,500 to conduct an inventory of dams that are 1-acre or larger within the District. The remaining fee of $25,000 was requested through the Hazard Mitigation Plan. In 2019, a contract was approved for a conceptual design of dams for multiple beneficial uses; evaluating up to 150 existing and potential dam and other structure sites. The project determines the localized water balance, recharge potential, storage capacity, design/construction considerations, and conceptual cost for dam improvement or new construction. The NRD received grant funding from the Water Sustainability Fund in the amount of $56,270.00 with the balance being funded by CPNRD in the amount of $84,410.
Construction to repair and/or remove dams on Box Elder, Clear Creek, and Jones Creek were approved for $47,150.
Box Elder 5A dam in Buffalo County needed channel improvements and dredging of sediment from the pool area.
Clear Creek 5 dam in Polk County required dredging and repair/modification to the drawdown pipe. Jones 1-1 dam,
also in Polk County, needed a riser and principal spillway replacement or slipline. Construction is expected to be
completed in spring of 2021. These three dams needed the most repair of the 40 dams that the NRD owns through
GRAND ISLAND DEWATERING STUDY
The NRD began participating in the Grand Island Dewatering System Study in September 2000. The Study identified a practical groundwater dewatering system to remove groundwater from residential basements and minimize impacts on the project area. The study also assessed potential transmission and discharge location options, financing options, potential impacts on water quality and quantity, and subsidence issues; using both low and high capacity vertical wells. The NRD delivered public opinion surveys to the northwest and southeast project areas prior to the initiation of the Study, with the majority of responses returned as “very interested” in the Study. The Study areas fall within the “Valleys” topographic region, characterized by low relief along streams that are underlain by alluvial clay, silt, sand and gravel. The general direction of groundwater flow is east to northeast generally paralleling the Platte River.
Evapotranspiration (ET) losses are relatively high due to a shallow water table; saturated thickness of Quaternary
deposits in/around Grand Island range between 80-200’. Depth to water table ranges from 5-20’ below ground level. In 2012, Olsson Associates presented a study to improve and expand the project implemented in 1998. The original study involved 29 dewatering wells compared to 33 in the 2012 study. 3 dewatering areas and areas of contamination were taken into account with wells proposed to be outside of those plumes. OA reported that the Grand Island City Council was initially receptive to the updates; however, there has been no further progress.