Tim Parkin - Landscape Photographer

The one thing I left out of last weeks blog post was information about tides and how to work around them. There is lots of tidal prediction software out there but I use ‘Mr Tides’ which does as good as any. The main thing to be concerned about is ensuring your tide program displays the sunrise and sunset times. This becomes very useful when trying to target a particular shot. Tidal prediction software isnt the end of the story however, three other things can effect the tide level.

Local Conditions

You can only generally get tide tables for a few different locations and so wherever you are, it is unlikeley to have the exact position specified. Generally, the water level will only vary by small amounts but if you are working somewhere within a harbour or tidal lake/loch, it may take the water longer to get into the area you are working which could cause delays of up to 30 or 40 minutes (I can’t find much information about this apart from conversations I have had with sailor friends. Any confirmation or refutation would be appreciated).

Wind Conditions

A strong and/or consistent onshore wind can push the water into the land (mostly getting traction on the waves) causing a ‘pile up’ and creating a possible 20-40cm increase in tide level. The opposte effect wil happen with an offf shore wind. Winds blowing parallel to the coast will advance or retard the time of high and low tide (by up to 20 mins or so) check the tide time further down the coast in the direction the wind is coming from.

Atmospheric Pressure

Tide tables are provided for an atmospheric pressure of 1013 hPa. However, for each additional Pascal of pressure, you get a 1cm lower tide (and vice versa). Pressure changes are not instant however and it can take hours to get a change in tidal level for a change in pressure (it takes longer on the east coast than the west coast according to my research?).

Overall, if you have very low pressure and strong onshore winds, you can have an enormous additional three meters of ‘storm surge’. Add this to a spring tide and you can understand why you get flooding.

Sand Erosion and Deposition

Whilst I was researching this, I also researched atmospheric effects on sand deposition and erosion (in an attempt to predict a good time to go back to Whitby Bay). The data is difficult to find but a couple of general rules can be inferred from the resources I read.

1) Calm summer weather causes sand levels to rise
2) Rough winter weather causes sand levels to lower

A consistent wind blowing along a shoreline transports sand up the shore in the same direction. This effect happens because as waves come in the sand is pushed up the beach a bit and then as the waves come back they move back again. The general movement cancels each other out but if the waves are coming in at an angle, the up and down movement will also include a sideway shift. For whitby beach (below the fairground) you really want the end of a strong winter storm with winds coming from the south.