BEsT MANAGEMENT PRACTICEs HANDbooK - Tahoe BMP

(1) The A values above, some to four decimal, are not intended to suggest that they are known to that accuracy, but rather arepresented for consistency and sensitivity tests of the effects of variation in grain size.(2) As an example of use of the values in the table, the A value for a median sand size of 0.24 mm is: A = 0.112m 1/3 – To convert Avalues to feet 1/3 units, multiple by (3.28) 1/3 = 1.49.Provide plans for re-nourishment and the rationale for those plans. These may include a proposed renourishmentfrequency or simply threshold conditions under which the re-nourishment would beproposed. For larger nourishment projects, estimation of typical and extreme wave conditions andsediment transport modeling may be appropriate.8.5.4 INSTALLATIONWhen installing a beach nourishment or replacement project, subaerial placement by conventionalconstruction equipment is normally acceptable. Include in the design plan all standard BMPs for theanticipated construction equipment (e.g. spill response, preventing sediment from entering the water,etc.). To ensure water quality, monitoring for turbidity during construction is recommended.8.5.5 MAINTENANCEA physical monitoring plan for a beach nourishment project consists of four major components: beachprofile surveys, beach sediment sampling, aerial shoreline photography, and wave and water surface levelmeasurements. These four components provide information required to document the physical responseand condition of a beach nourishment project. During this phase, data are gathered to confirm that theproject design is performing as expected and to identify potential design problems such as erosion areas,unexpected project impacts, or inadequate design volumes and cross-section dimensions. If problems areidentified, the monitoring data provides information for developing solutions and improving projectperformance based on an understanding of the physical processes. The second phase of the plan employsan operational level of monitoring to annually assess the condition of the project. This phase ofmonitoring also provides information for assessing longer-term aspects of project performance. 41The maintenance of beach fill depends on its coarseness and on how quickly it erodes. Thus, periodicaddition of fill material will likely be required as erosion continues. There are several time scales ofimportance with regard to wave climate that must be known. The design life of a beach nourishmentproject is usually 10 years or more and periodic re-nourishment is typically done every 3 to 5 years. 42Periodic re-nourishment can begin immediately after construction; fill material will be lost from theproject due to lateral spreading from the time of deposition. Periodic re-nourishment will be required tomaintain the desired beach cross section, especially just after construction. It should be recognized by thedesigner that year-to-year loss rates could deviate from the long-term average erosion rates. In addition toend effects at transitional areas, losses can be significantly influenced by the occurrence of major storms.Annual losses will vary from year to year depending on storm severity and frequency. Therefore, whilean average re-nourishment interval and quantity can be estimated, the actual required interval andquantity will vary depending on the wave climate conditions that occur. Ideally, the need for re-41USACE, 2008, Coastal Engineering Manual - Parts I-642USACE, 2008, Coastal Engineering Manual - Parts I-6CHAPTER 8: Shorezone Protective Structures and BMPsTRPA BMP Handbook8.5 Beach Nourishment and Replenishment 2012Page 8-46