The Natomas Basin is surrounded by 42 miles of levees that provide protection from the American River, Sacramento River, Natomas Cross Canal and Natomas East Main Drain Canal. Improvements to the levees were constructed in the early 1990’s, which consisted of raising levees along the streams and canal systems. However, as other risk factors, including susceptibility to under seepage, began to generate increased concern, particularly following the 1997 flood event in the Sacramento Valley, it became clear that additional levee improvements would be needed in the Natomas Basin.
In 2006, the U.S. Army Corps of Engineers (USACE) determined the Natomas Basin had less than a 100-year level of flood protection due to the threat of deep under seepage. In 2007, SAFCA and the State of California began constructing levee improvements while USACE sought Congressional approval and appropriations for the work. These improvements included the construction of deep cutoff walls, landside berms, and a new adjacent levee along a portion of the Sacramento River East Levee to prevent under seepage.
By 2013, SAFCA and the state completed 18.3 of the 42 miles of levee improvements required to meet current flood control standards. In 2019, USACE began construction on the additional 24 miles of levee improvements necessary to provide a minimum 200-year level of flood protection to the Natomas Basin.