CS13A - Concurrent Session 13A: National Inventory of Low-head Dams: completion and next steps

The Task Force to Create a National Inventory of Low-head Dams was established by the Association of State Dam Safety Officials (ASDSO) in 2020 with a simple and single purpose: locate all low-head dams in the U.S. using latitude and longitude. The purpose of this paper is to describe the successes and lessons learned in this process, and to make recommendations for next steps. An initial and ongoing challenge is to define a low-head dam. For example, should structures on irrigation canals and stream ford crossings be included? To be as complete as possible, all such structures are included in the inventory. Additionally, a maximum dam height limit for a “low-head” dam has been discussed at length. For purposes of the inventory, a maximum height of 25-feet was set to coincide with the minimum height associated with the National Inventory of Dams (NID). Determining what low-head dam data already exists has taken two-plus years. Data gathering and development has been most successful through the Google Earth Pro and State and Regional Entities subcommittees. These two committees have gathered the majority of the dams that is currently in the database. Currently, the data gathered by the committees are undergoing a quality control check by experienced professionals. Challenges for the Task Force have included: (1) concerns from some states that an inventory will increase exposure to litigation, (2) finding professionals willing to perform quality control on identified low-head dam sites, and (3) reconciling data from disparate sources. This 100% volunteer work effort is nearing completion and will provide all states and NGOs valuable information about the location and extent of low-head dams in the U.S. The final product will include a map similar to the National Inventory of Dams map with latitude and longitude at a minimum Future steps for the inventory may take several paths. For example, the WRDA bill of 2022 authorized 30 million dollars to the U.S. Army Corps of Engineers to create the same inventory and to add attributes such as dimensions and ownership; funding is not yet appropriated. We recommend that an effort to determine the occurrence of submerged hydraulic jumps at low-head dams be undertaken as a next step and followed by an assessment of each dam’s potential public hazard based on risk factors such as submerged hydraulic jump potential, recreational usage of the waterway and proximity of the dam to inhabited areas.