Sedimentation and Small Dams

Humankind have long built dams to provide resilience against droughts and floods. From the plains of the agricultural regions of Wadi Rajul of Jordon in the fourth millennium BCE to the modern United States, dams have served as vital pieces of economic infrastructure. The design functions provided by any dam are subject to degradation as sediment flows through the waterways and fills the storage behind the dam. Sustainable sediment management in reservoirs seeks to preserve long-term capacity by incorporating appropriate sediment management features into designs of new dams, implementing soil and water conservation practices in the watershed, stabilizing streambanks and waterways, and potentially modifying existing structures to retard the rate of sediment accumulation. The intent is to achieve a long-term sediment balance that preserves useful storage. This paper outlines the scope of this historic problem and how sedimentation continues to adversely affect modern dam infrastructure with a focus on small dams and waterways. Also discussed are techniques used to address the sedimentation issues as well as remedial actions. This presentation includes an overview of the variety of analyses and design techniques employed by the United States Department of Agriculture’s Natural Resource Conservation Service (USDA–NRCS) in the planning, design, and maintenance of watershed or river/stream projects. This presentation discusses the scope of the problem and provides an overview of the methods used to model and predict sedimentation.