Professional Presentations:

Deformation of Delta Levees; Tillis, R. Kevin; CALFED Bay-Delta Program Science Conference, Sacramento, CA; October 2004.

Delta levees constructed on weak marsh (peat) deposits have a long history of settlement and lateral deformation.  The settlement and deformation leads to loss of critical freeboard for the levee crest, increasing the risk of overtopping.  To maintain adequate freeboard and levee crest width, additional fill is placed.  Additional settlement and lateral deformation occurs under the weight of the new fill.

A better understanding of levee deformation is useful in assessing the safety of the existing levees and in developing alternatives for levee rehabilitation.  To collect data on the amount of levee deformation, slope inclinometers were installed in existing levees.  Both settlement and lateral deformation were measured during and after fill was placed to raise the levee crest and buttress the levee.  In addition, a separate test fill was constructed over peat ground and vertical and lateral deformations were measured.  Lateral deformation from between a few inches to over a foot toward the island interior were measured in the existing levee due to placement of fill.  The deformation continues well after the fill placement.