Bluffs
Forms
Drift
Storms
Slides
 
Shore Forms  
 
A gallery of beach shapes can be found along Puget Sound. As waves sweep materials along the shore, beaches form where sediments collect. Eroding bluffs often provide building materials for shore forms. Rivers and streams may also add sediments. Waves and currents sort these materials, and deposit them on a bar, spit, cuspate foreland, tombolo, or beach.
Dungeness Spit, Clallam County.
 
A double tombolo, Decatur Head, Decatur Island, San Juan Islands.

Shore Forms: A Gallery

  • Spit
    A spit is a strip of beach which extends into deeper water. Most spits along Puget Sound straighten a curving shoreline. Spits often form a straight ridge of sediment across a bay. Spits commonly develop in the direction of shore drift.
  •  
     
    Some spits jut out from the mainland like an arm. Dungeness Spit, a large arm with complex barbs and hooks, is one of the largest natural spits in the world.  
     
  • Tombolo
    Tombolo, an Italian term, is a spit or bar connecting an island to the mainland. Tombolos form in areas protected from large waves. The sediments to make a tombolo can come from the mainland beach or the island. A single tombolo is a single ridge connecting to an island.
  •  
     
  • Double Tombolo
    A double tombolo has two ridges extending to shore. Double tombolos can form in areas where there is a seasonal shift in shore drift.
  •  
     
  • Cuspate Foreland
    Cuspate forelands are triangular points or capes made from sediment deposits. Along Puget Sound, forelands can stretch from a few acres to a few miles. In many cases, forelands are created when two shore drift directions meet.
  •  
     
  • Bar
    Bars are ridges of sand seen when tides are low. Bars can be unstable, shifting with storms and seasons. During storms, bars can break the force of big waves.
  •  
     
  • Looped Bar
    Wind and waves have curved this finger of land into a loop. Looped bars often shelter a small lagoon, bay, or marsh.
  •  
     
  • Delta
    Deltas form where streams and rivers deposit sediments faster than waves can remove them. An array of deltas can be found along Puget Sound.

  • Shore Shelter

    Shore forms provide homes for wildlife. Shorebirds and gulls feed on bars, spits, and tombolos. The heads of bays, spits, and cuspate forelands provide breeding areas for fish such as sand lance and surf smelt. Ridges of sand, gravel, and cobble can harbor a variety of invertebrates, seaweed, littleneck, butter, and horse clams.

    Bald eagles and other birds use drift logs on spits for perches during the day. In summer months, Harbor seals may give birth to and nurse pups on bars.
    Drift logs on Dungeness Spit provide perches for birds.
     

    Shore Forms: Shifting Shapes

    • Most shore forms are subject to cycles of erosion and rebuilding.
    • Bars, forelands, and spits are attractive spots for development because they offer easy access to the beach. Be cautious about buying property in these areas ­ flooding and erosion can be a problem. Check with neighbors and local building officials.
     
    Related Topics

    Spits, Changing shore shapes.
    Dungeness Spit, Wind, waves, and eroding bluffs.
    Drift, Materials on the move.
    Floods, Investigate before buying land.

    Related Links

    Puget Sound Nearshore Environments, Accreting Beach and Development, King County Department of Natural Resources. Accretion beaches and the effects of docks and bulkheads; two color illustrations.

    Coastal Change: Natural Processes, USGS.
    How coastal lands and sediments are in constant motion.  

    back next
     
    Home - Tour - Beaches - Bluffs & Spits - Species
    Buying Property - Building - Homeowner Tips - Laws & Permits
    Site Map - Links - Credits - Shorelands Home - Ecology Home
     
    Comments? E-mail: Shellyne Grisham