page_title: Jamestown Dam
section_title: Flood control
hierarchical_section_title: Jamestown Dam / Dam and reservoir / Flood control
caption_attribution_description: English: Map of the course and drainage basin of the James River in the US states of North Dakota and South Dakota.
context_page_description: The Jamestown Dam is a rolled-earth dam spanning the James River in Stutsman County in the U.S. state of North Dakota, serving the primary purpose of flood control. It is north of the city of Jamestown, North Dakota. Built from April 1952 to September 1953, the dam measures 1,418 feet long at the crest and 85 feet high. It impounds the James River to form the Jamestown Reservoir. A small islet lies shortly upstream of the dam, where the James River previously split into two channels.
  The dam and reservoir rest on a wide plain of shale where the James River cut a canyon up to 1 mile wide and 100 feet deep. The shale has a dark gray, bedded appearance, and is mostly claystone or siltstone. The valley also contains many traces of alluvium, mainly deposited during the last ice age when the area was heavily glaciated.
context_section_description: The Jamestown Dam's primary purpose is flood control, and has prevented approximately $36 million in flood-related damages. When it was constructed, certain deficiencies were noted in the foundations for the dam. When the reservoir is at normal levels, the failure risk is small, but as the water level rises, the potential for collapse increases. Floods in May 1969 caused the reservoir to rise to its record level, over 105,000 acre feet (130,000,000 m³), causing leakage of the dam. This level was not even half the reservoir's maximum capacity of 230,000 acre feet (280,000,000 m³). In 1993 and 1995, floods caused the lake to rise to within 1 foot (0.3 m) of the 1969 level. An inspection by the Bureau of Reclamation's Dam Safety Department revealed that the dam could potentially fail if the deficiencies were not corrected. As a result, eight relief wells (wells that drain a pervious stratum) were installed in the dam in 1995, and a heavy gravel filter blanket to prevent erosion of embankment materials during seepage was constructed in the spring of 1996.
caption: James River watershed
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