BEsT MANAGEMENT PRACTICEs HANDbooK - Tahoe BMP

8.2 BULKHEADS AND LAKE WALLS8.2.1 OVERVIEWA bulkhead is a vertical wall designed to prevent backshore erosion andprevent hillslope mass movement. These types of retaining walls are primarilyconstructed to hold or prevent sliding of the backshore soil while providinglimited protection from wave action. These structures are also used to stabilizea commercial marina navigational channel or basin that has been establishedand maintained by dredging.The primary purpose of a lake wall was originally to prevent inland floodingfrom major storm events that are accompanied by large and powerful waves.The key functional element in lake wall design is the calculation of the crestelevation in order to minimize the overtopping from storm surge and waverun-up.Bulkheads and lake walls are most applicable to backshore settings comprisedof low bluffs which might otherwise fail and collapse towards the foreshore.The bulkhead protects the eroding bluffs by retaining soil at the toe, therebyincreasing upper hill slope stability. Bulkheads are also applicable at marinaswhere water depth and a fixed channel position need to be maintained.Bulkheads are designed to protect eroding slopes that are not liable to failureand collapse but are often used where a sloping revetment may not be feasible.This determination must be made during the initial planning stages when theexisting conditions and impacts analyses are being conducted. Bulkheads can beused for the rare reclamation project where beach fill is needed at a position inthe existing foreshore.Use bulkheads only where protection of the backshore is determined to be ofgreater value than beach preservation. Bulkheads can be grouped into threegeneral categories based on the support structure employed to ensure stability(Refer to Table 8-6). Numerous modifications of these types and hybridstructures are also in use.Table 8-6: Overview of Bulkhead and Lake Wall StructuresTYPESheet PileSUPPORTSTRUCTURECantileverAnchoredDESCRIPTIONDerive their support from ground penetration; therefore, theeffective embedment length must be sufficient to preventoverturning.Similar to cantilevered bulkheads except they gain additionalsupport from anchors embedded on the landward side or fromstructural piles placed appropriately deep on the lakeward side.Corrosion protection at the connecting fixtures is particularlyimportant in avoiding structural failure.TRPA BMP HandbookCHAPTER 8: Shorezone Protective Structures and BMPs2012 8.2 Bulkheads and Lake WallsPage 8-21