Back in May 2005 a team of researchers (myself included) from the University of Plymouth were based in Sennen Cove (working out of the Black Hut). We spent around 3 weeks continously monitoring the change in the shape of the beach (the beach profile) and making a multitude of measurements such as the wave conditions, current strengths, suspended sediment concentrations, sand ripple sizes etc. This effort was part of a research project (called X-SHORE) funded by the Natural Environment Research Council which was designed to further understanding of the processes that move sand in the cross-shore direction (i.e. on and offshore) and to lead to improved capability to model how beaches respond to changing wave conditions. Our project also involved a similar period of field measurements at a beach in western France in May 2006 and since completing this work we have been beavering away to make sense of the measurements and draw together all the information we gathered. You probably won't be surprised to learn that it is incredibly difficult to make good quality measurements in the challenging environment that is the surf zone but this is an area of research that is a major specialism at the University of Plymouth so we have had some success (we think!). A key component of the work since the experimental campaign has been carried out by a PhD student under my supervision and this is now approaching the final stages with the work being written up for examination and publication. It's worth noting that the intention was not that we would be able to predict in detail the way that the beach at Sennen Cove changes, but rather to use Sennen and our site in France to get new data to explore this subject in a more general sense (the ability to model in detail how a particular real beach responds to changing wave conditions is, sadly, still some way off, partly because it is so hard to get good data of beach processes and so rather few people actually try to get any!).
Anyway, what we found at Sennen Cove was consistent with what has been found out in other field studies, namely that in general sand moves offshore during storm conditions moving towards a location roughly at the position where waves begin to break (often forming a 'break-point' sand bar) whereas in calm conditions much less sand moves but it tends to shift back towards the beach-face. This basic idea is well known and those of you who spend a lot of time on local beaches will be familiar with this pattern even if the details of the processes that cause the sand to move are something of a mystery. What we have managed to do which has not been done much before is to quantify the relative strengths of the offshore and onshore sand transport that occur during storm and calm conditions respectively and get a much better understanding of how this cross-shore sand transport varies with position down the beach and of the processes responsible.
As far as the recent storm conditions are concerned, because these were exceptionally large I would expect that the amount of sand stripped off the beach would be much greater than normal, but perhaps most importantly that this sand will have been moved further offshore (so to much deeper water) than normal also. This could well mean that whereas the waves in calm conditions can usually gradually push the sand back onto the beach, the sand moved offshore recently may now be in water so deep that these smaller waves do little to shift it back onshore, or if there is onshore movement it will be very weak and very slow and so it will take a long time for the beach to recover. In fact, it may take more storms (but with smaller waves than the recent storms) to nudge the sand back onshore to a depth where the waves in calm conditions can have any effect on it. Time will tell, but I would not expect the sand to get back onto the beach anytime soon although beaches are notoriously complex systems so it's not impossible.
As an aside, the time I spent down in Sennen Cove in May 2005 left a deep impression on me. I subsequently came back in July 2005 with my wife and two daughters for a holiday and have returned each year since, staying each time at different properties in Harbour Mews. My whole family love Sennen Cove, but sadly it looks like it will be difficult for us to return again this year. Perhaps if I don't make it, the sand that has recently left the beach will!
I’d like to second what John said, and add my personal thanks to Terry for those, and all the other great images, he posts. My daily visit to the site truly does keep me “homesick” for Sennen. The Midwinters are coming to stay with us “down under” in April, proper job!
Sand is mobile and is likely to be washed back in eventually. In fact
it's only a thin covering over a substrate of rock, mud or soil.
At Westward Ho! in the 1970s the sand from the beach disappeared
completely and it left what was in effect a Mesolithic Marsh landscape
with preserced hazelnuts. You can still see this at extreme low tides
there. When the beach disappeared the local council debated what to do
as it was really messing up the tourist trade. But then one night it all
At Long Rock the sand covers mud - relict alder forests are in Mounts
Bay. At Praa the beach covers turf - dig down and you can still find
grass. Use of these turves for tin capture was mentioned by Justin
Brooke in The Tin Streams of Wendron and journeys were made to collect
from there. There is (was) a little left at the back of the beach.
And at Porth Ledden the beach was at one time sandy - Tristn (of him and
Isolde) is supposed to have fled to Ireland from here and Athelstan
launched his attach on the Vikings on the Scillies from that place (and
then built the church at St Buryan as thanks). But the sand disappeared
after attempts in the 1920s to recover alluvial tin, the beach
destabilised and went and hasn't returned since (this was told to me by
Willie Alford whilst we sat at Kenidjack Castle one bright April
afternoon some few years ago).
I would like to investigate (and I can't immediately being 300 miles
away) what's happened to the sand at Porth Nanven.
Adn of course the cliffs of head (periglacially eroded material) behind
the beaches at Top Tieb, Marazion, Praa Sands itself and a very
precarious house at Perranuthnoe (I think) have all been at risk for years.
At Coverack storms in 1994 really covered up some unique geological
exposures just underneath the sea wall. The geology there was cricial in
the understanding of the Lizard complex as an ophiolite - a piece of
obducted oceanic crust. The nearest better exposure of anything similar
is in Oman, so this is why it's important.
But back to Sennen - nothing can be predicted with certainty - we can
But it would be a good oceanographic research project - Terry George has
perhaps one of the best continuous photographic archives of the beach at
Sennen, especialy the beach, so maybe someone at Southampton
(http://www.noc.soton.ac.uk/) would be interested.
postscript to previous post
I now wonder what it's like at Porthmeor? That bay is the northern
exposure of the Land's End Granite against the killas. Any movements
there would be geologically interesting.
Just wonder of the stroms at Sennen have exposed anything interesting of
a Bronze Age nature. I'm remembering when the cable trenches were dug
and there were archaeological finds of that age. And of course the
cables themselves may be more exposed after the storms - and so
susceptible to damage.