An Ocean Blueprint for the 21st Century - California Ocean ...

Figure 12.1 Dams Impede SedimentDestined for the CoastOther federal programs have less direct, but no less important impacts on sediment.The U.S. Department of Agriculture’s Natural Resources Conservation Service plays a centralrole in efforts to reduce agricultural soil erosion, much of which finds its way to estuariesand the ocean. USACE and DOI’s Bureau of Reclamation operate flood control, waterstorage, and hydroelectric projects which retain, and occasionally release, large amountsof sediment. Sediment also is addressed extensively through the nation’s regulation ofpoint and nonpoint sources of pollution, with EPA and NOAA as the principal federalagencies involved.Some activities that affect sediment, such as dredging and shoreline erosion controlprojects, fall under specific laws, often implemented in isolation from each other. Otheractivities are addressed under broader, less specific authorities. Even seemingly welldesigned projects can sometimes create more problems than they solve, or encounter frustratingdelays, because of poor communication among stakeholders, and confusion aboutthe many programs that remove, relocate, prevent, oraccelerate the transport of sediment. At this time,there is no consistent mechanism to ensure that eachindividual sediment-related project is considered in alarger ecosystem-based context.Altering Sediments throughHuman InterventionChanging Sediment Quantities■ Dam LocationTo support California’s exponential population growth, over1,400 dams have been constructed across the state for anumber of purposes, including water storage, irrigation, floodcontrol, recreation, and hydroelectric power. However, damsconstructed in coastal watersheds block the flow of sedimentsneeded for natural beach replenishment.Source: California Department of Boating and Waterways.“California Beach Restoration Study.” (Accessed May 2004).Many human interventions in sediment processes areunintentional, occurring as a by-product of routineeconomic activities that overload or deprive naturalsystems of sediment. Activities such as forestry, agriculture,and urban development yield great benefitsto the nation, but also accelerate natural erosion.Excess sediment suspended in the water column oraccumulated at the bottom of water bodies can createproblems for other industries, such as shipping, fishing,and tourism, and can harm aquatic life.Conversely, flood control, water supply, andhydroelectric projects prevent the natural movementof sediment, contributing to downstream erosion andsubsidence problems (Figure 12.1). As older componentsof this infrastructure become too costly tomaintain, or are rendered obsolete for structural oreconomic reasons, disposing of the enormous quantitiesof trapped sediment will pose a new set of problems.Development in coastal communities can alsodisrupt natural sediment movement, causing erosionin some places and accretion in others. Such projectsmay have unintended effects on neighboring jurisdictions,both upstream and downstream, that had norole in the planning process.182 A N O CEAN B LUEPRINT FOR THE 21ST C ENTURY