Page 20 - 2021PSF-ResilientCoastsForSalmon-NewLogo-Primer-Web

Photos by: Mitch Miller

Longshore Drift
Have you ever noticed that when you’re resting
on a floatie or paddling in a kayak, that the water
tends to push you in either direction along the
shoreline? Well, this is the same force that transports
sediment parallel to the beach . This process is called
longshore drift, and it is a combination of currents,
incoming wave direction, and sometimes wind .
Once the sediment is picked up and suspended
in the water, it can be moved along the shoreline
for many kilometers! The shape of the shoreline,
including human-made structures, determines
where that sediment is ‘dropped off .’ Littoral drift
is the movement of sediment along the shore by
longshore drift . Longshore and littoral drift are
critical to creating and maintaining our beaches .

Waves
Waves typically hit the shorelines at an angle
(refracted) and that results in energy being directed
along the coastline in the direction of the incoming
wave . This energy, known as longshore current, is
similar to longshore drift and also contributes to
erosion, deposition and transport of sediment .
Wave energy works in multiple ways to transport
and redistribute sediment . As a wave approaches
the shore it enters shallow water and the wave base In high energy shores that experience lots of wave
scours the bottom, creating turbulence and picking exposure, sands can be deposited and washed
up sediment . As the wave crests and crashes onto away seasonally with storms . Steady supplies of
the shore, the sediment is further disrupted and sediments being delivered by longshore drift
picked up into the water column . The uprush of processes allow accretion into dunes which
water that moves onto the beach is called swash become stabilized with vegetation and offer
— this hits the beach, then the water retreats protection to the areas above the tidal zone .
back over the sand and stones as the next wave As sea levels change these buffers naturally
approaches the shore . migrate and continue to protect our shores .

19