Hartlepool (beach, washover fan)

Hartlepool (County Dorham)  1 Mar., 2019

Keywords: Beach, Sedimentology, Washover fan

I visited Hartlepool for research meeting and observed beach there on the way.

Hartlepool is located along the east coast of Britain Island and faces the North Sea. The town has developed from the 7th century around the abbey in Headland which is a spit, and large port is located at the base of the spit (Fig. 1).

Fig. 1. Locality of Hartlepool. In the northern coast of Hartlepool, there two or three rows of longitudinal bars in front of beach.

The North Sea side of Headland is a rocky (Fig. 2), and there is a sandy beach on the north side (Fig. 3), and I observed the sandy beach.

Fig. 2. North Sea side coast of Headland (Eastern coast of Hartlepool).

Fig. 3. Northern coast of Hartlepool.

According to satellite images (Fig. 1), there are two or three rows of longitudinal bars on the beach but most of them were submerged except for the bar described later because I visited there during high tide. The waves were breaking several hundred meters off the coast, so there is probably a bar there (Fig. 4).

Fig. 4. Wave break on submerged bars several hundred meters off the coast.

A bar was exposed several hundred meters north of Headland (Fig. 3). The surface was flat for the waves to be washed, and the crescent-shaped scours developed on the seaward side of gravels on the sand (Fig. 5).

Fig. 5. Surface of the bar.

There are low points in the bar every several tens meters, and the great waves pass through it to runnel which is the water area located between the bar and foreshore (Fig. 6). 

Fig. 6. Timelaps pictures of washover. Left: whole view. Right: close view.

This washover occurred as often as once every few minutes. It is closer to the actual situation that the great waves beyond the top of the bar change to sheet flows and flow down to the runnel, rather than the waves just passing over. Channels with low relief were formed when flowing down, more water flow concentrated to there and was further developed, and fans were formed on the runnel side of the bar.

In addition, in places where waves reach once in a few minutes, air bubbles from sand immediately after the waves are covered, leaving holes of about 2 mm in diameter (Fig. 5).