Approved by the Energy, Environment, and Water Policy Committee on February 2, 2011
Approved by the Public Policy Committee on February 7, 2011
Adopted by the Board of Direction on April 1, 2011
The American Society of Civil Engineers (ASCE) supports the onshore or near-shore placement of clean sand dredged from navigation projects, tidal inlets and estuaries. Beach-quality sediment and sand dredged from navigation projects and inlets should be placed on beaches that most need nourishment to reduce the effects of erosion. ASCE encourages regional sediment management and coordination among planners of coastal navigation projects and beach erosion control projects to ensure that beach-quality sediment and sand dredged from inlets is not disposed of offshore, but is returned to the coastal system from which it originated.
Often there is little coordination between government agencies concerned with maintaining safe navigation channels through coastal inlets and those agencies and local jurisdictions concerned with beach erosion. Quite often the problem is due to different funding sources for the two projects. The economic feasibility of navigation channel maintenance and beach erosion control projects are usually assessed independently of each other. Thus, minimizing the cost of an inlet navigation project often dictates that sand dredged from the inlet be disposed offshore. At the same time, nearby beaches may experience severe erosion because sand in transport along the shore is trapped by the inlet and removed from the beach and coastal systems.
The most logical source of sand to nourish eroding beaches is often a nearby inlet since inlet sand usually has the same textural characteristics as the beach sand. The combined cost of a coordinated channel dredging and beach nourishment project might often be lower than the sum of the two separate projects. However, because of different funding sources and lack of coordination, the two projects are often executed independently at a higher overall cost and waste of taxpayer's money.
Tidal inlets provide an important physical connection between the ocean and back bay areas. They are both commercially and ecologically significant. They provide a path for fish and fish larvae to travel between the nutrient rich back bays and the ocean as well as a path for recreational and commercial vessels to travel between the ocean and the safety of inland ports. Recreational and commercial vessels require adequate water depths to navigate safely through such inlets. Also, a relatively fixed channel location is important so that it can be adequately marked by buoys and other aids‑to‑navigation. To insure safe navigation, periodic dredging of inlet channels is usually necessary.
Tidal inlets also trap sand carried along the shoreline by wave‑driven longshore currents. They serve as the conduits that remove sand from the active littoral zone and carry it into sheltered waters behind the inlet where it is deposited. The loss of sand from ocean beaches into inlets contributes to erosion problems near inlets and along downdrift beaches. Thus, sand deposited in inlet navigation channels almost always has as its source the adjacent ocean beaches.
ASCE Policy Statement 349
First Approved in 1989