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Title: Techniques in evaluating suitability of borrow material for beach nourishment
Authors: James, William R.
Keywords: Beach erosion
Beach nourishment
Borrow material
Grain-size distribution
Renourishment factor
Publisher: Coastal Engineering Research Center (U.S.)
Engineer Research and Development Center (U.S.)
Series/Report no.: Technical memorandum (Coastal Engineering Research Center (U.S.)) ; no.60.
Description: Technical Memorandum
Abstract: Selection of borrow material for use in beach restoration and periodic nourishment requires analysis of the textural differences between the potential borrow and native beach materials. Three quantitative techniques proposed for such analysis are reviewed and compared, and guidelines are suggested for use in planning and designing projects requiring beach nourishment. The techniques are of two types. One is based on the assumption that sorting processes will selectively remove borrow material from the various size classes until a "stable grain-size distribution" (gsd) is obtained and the placed fill is stabilized. The gsd of the native material is used to predict the character of the stable gsd. Methods of this type lead to calculation of a "fill factor," an estimate of volume of borrow material required to produce a unit volume of stable beach material. Methods of this type have been proposed by Krumbein and James (1965), and by Dean (1974); the former provides the basis for the method described in the Shore Protection Manual (U.S. Army, Corps of Engineers, Coastal Engineering Research Center, 1973). Examination of the conceptual basis for each method suggests that the SPM method may overestimate fill factors whereas Dean’s method may underestimate them. A modification in the assumptions underlying the SPM method results in an approach which appears to represent a satisfactory compromise between these alternatives. Another type of technique was proposed by James (1974). It is based on the assumption that no material is absolutely stable, but that erosion rates depend in part on the gsd of the material exposed to existing coastal processes. Prediction of erosion rates associated with a given borrow material is based on observation of erosion rates and textural properties associated with native materials. This method results in a "renourishment factor" for determining volumetric requirements for periodic nourishment. Practical application of any of the methods is dependent on the engineering design, the historical behavior of the beach in the project area, and the techniques of handling the borrow material before and during its placement.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Technical Memorandum

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