In the 1600s, the Hyle/Hoyle “lake” was a channel, 30ft deep at the Dovepoint end, and 15ft deep at the Hilbre end. It was deep enough for the largest ships using the coast to moor at low water. Silt from mostly the Dee but also the Mersey was deposited in the channel over time and it gradually filled. By the late 1800s there was still enough water close off shore to allow the substantial Hoylake fishing fleet to anchor there. (1)
When the promenade was built, only the eastern part of the channel was water at low tide, but there was still a channel around 200m from the promenade, filled with water twice a day and protected the promenade from sand blowing in from the East Hoyle bank. (2)
That channel continued to fill with silt, though water with a heavy load of silt would still arrive from east and west each tide. This too acted as a barrier to windblown sand, though the beach level continued to rise and become flatter.
Today the beach level measured at 200m offshore is around 6-7m higher. It is almost flat (a 1 in 400 gradient). Sand has finally covered over the silt, at least to level with the Old Baths, and there is no gutter to bring silt in from the Dee. The mean high tide mark is retreating seaward at an astounding 7m a year and the upper beach is now above the astronomical high tide mark (which is why dune plants are able to establish).
As sand continues to blow in, some of it will be trapped by the seaward edge of the green beach which will rise into a ridge, further protecting the upper beach from seawater. (3)
The height and position of those dunes will be determined by the relative contribution of sand delivery and tidal scour but an equilibrium will be found. They will start on the outer edge of the main vegetation line and adjust outwards. A dune slack will form behind.
References
- Hoylake’s fishing fleet at anchor, dunes and bathing machines prior to the promenade, Young, D, More pictures from the past.
- Children paddling in the Hoyle Gutter, showing the proximity if water and the steep profile of the beach Young, D Ibid.
- Sand dune formation and succession: Short video tutorial Universities of Cambridge/Derby
