A sand beach exist because there is a balance between the supply and removal of the material that form it. Dynamic equilibrium a process that happened a long the time. Supply is equal to the removal of material. The beach is continually changing It appear unchanged and remain in balance
NATURAL PROCESSES
Onshore Current :
- waves moving towards the beach
- Produce current in surf zone
- Move water onshore and along the beach
Onshore Transport :
A current transport suspended sediment towards the shore
Longshore Current :
- wave will not approach the beach paralely
- Strike the beach with slight angle
- This current moves down the beach
LONGSHORE TRANSPORT
- Turbulence occurs as the waves break in the surf zone
- Tumbles the beach material into suspension
- The existence of longshore current
- Displace the sediment down the shore
- Producing longshore transport
RIP CURRENT
- Onshore transport accumulate water and sediments/sand
- This water flow back to the sea
- It repeat all the time
- Region where water return seawards is narrow
- Make the flow of water Fast moving
- This is RIP CURRENT
ESTUARIES
- River mouth, fjords, fault bays, and other semi-enclosed body of salt water are all parts of the coastal zone.
- If one of these has a free connection with the ocean
- If it diluted with fresh water
- If average salinity lower than the adjacent of the sea
- This an estuary
TYPE OF ESTUAIES BASED ON THE CIRCULATION AND SALINITY DISTRIBUTION
SALT WEDGE ESTUARY
- Occur with in the mouth of a river flowing directly into salt water
- Fresh water flows rapidly out to sea at surface
- The denser sea water flow upstream along the river bottom
- Seawater held back by the flow of the river
- Form a sharp density boundary of salinity
WELL MIXED ESTUARY
- Have strong tidal mixing and low river flow
- Creating slow seaward flow of water at all depth
- Due to strong tidal turbulence the salinity will uniform over depths and decrease from the ocean to the river
- There is a little or no transport of seawater inward at depth; instead salt is transferred inwards by turbulence diffusion.
PARTIALLY MIXED ESTUARIES
- Have strong net seaward surface flow of fresh water and strong inflow of sea water at depth
- Sea water is mixed upward and combined with the river water by tidal current turbulence
- Entrainment to produce a seaward surface flow that is larger than that of the river water alone
FJORD-TYPE ESTUARY
- Deep, small surface area estuary
- Moderately high river input
- Little tidal mixing
- The river water tend to remain at the surface
- Move seaward with little mixing of the underlying salt water
