What is meant by littoral drift?

Littoral drift or longshore sediment transport is the term used for the longshore transport of sediments (mainly sand), along the upper shoreface due to the action of breaking and longshore currents.

What is the difference between littoral drift and longshore drift?

Longshore drift is simply the sediment moved by the longshore current. This current and sediment movement occur within the surf zone. The process is also known as littoral drift. Beach sand is also moved on such oblique wind days, due to the swash and backwash of water on the beach.

Why is littoral drift important?

Longshore Drift (littoral drift) Longshore drift is a process responsible for moving significant amounts of sediment along the coast. The swash moves beach material along the beach and the backwash, under gravity, pulls the material back down the beach at right angles to the coastline.

What causes Littorals?

It is caused by large swells sweeping into the shoreline at an angle and pushing water down the length of the beach in one direction. Longsshore currents usually extend from the shallow waters inside the breaking waves to breaking waves on the outside.

What is a littoral cell?

Littoral Cells. ll coasts are divided into natural compartments called littoral cells. Each cell contains a complete cycle of sedimentation including sources, transport paths, and sinks. The presence of sand on any particular beach depends on the transport of sand within the cell.

What causes longshore drift?

Longshore currents develop when waves approach a beach at an angle (Figure 12.37). Longshore currents cause sediment transport called longshore drift. Longshore drift is the movement of sediments along a coast by waves that approach at an angle to the shore but then the swash recedes directly away from it.

What causes beach drift?

As wind-driven waves approach the shoreline at a slight angle, sediments are carried along the coast. Waves move sediments along the beach in a zigzag fashion (red arrows). The majority of sediment is transported in the surf zone. The movement of sand along the shoreline is known as beach drift.

How does a littoral cell work?

A littoral cell is a coastal compartment that contains a complete cycle of sedimentation including sources, transport paths, and sinks. For example, along mountainous coasts with submarine canyons, cell boundaries usually occur at rocky headlands that intercept transport paths.

How is littoral drift related to the longshore current?

Longshore sediment transport is closely related to the longshore current that is generated when waves break obliquely to the coast. The yearly littoral drift associated with the waves will often be the dominant factor in the sediment budget for an exposed coastline.

What is the formula for littoral drift in water?

The formula reads: U ¯ = depth-averaged current velocity, Urms = root-mean-square wave orbital velocity, U ¯ c r = critical current velocity, β = bed slope in current direction (positive uphill), h = water depth, d50 = median grain diameter, z0 = bed roughness ≃ 0.006 m, s = relative density of sediment and with v = kinematic viscosity of water.

When was the first littoral current model made?

Bijker’s (1971) made the first detailed longshore sediment transport model, using the littoral current model of Longuet-Higgins (1970) for a beach of constant slope together with a sediment transport model for wave and currents.

Why does sand drift around the harbor entrance?

The original harbor entrance faced east (out to sea), but accumulation of sand on the south side built the shoreline seaward until sand began to drift around the eastern end, causing shoaling of the harbor entrance.