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AQUAVAIL LTD

Site surveys, condition reports and specifications · Christchurch, Dorset

Sheet 05

Tides, access and weather windows on an exposed frontage

On a sheltered site the working day is the daylight. On an exposed frontage it is the part of the daylight when the face is out of the water, the wind is off the instrument and the ground underfoot will hold a tripod.

What the tide leaves of a day

A frontage is readable for the hours its toe is clear of the water, and those hours move through the day across a fortnight. The same wall that can be read at nine in the morning this week is under water at nine next week, so a survey of a long frontage is planned as a set of windows rather than as a set of days.

How a working window moves through successive days Four stacked bars, one for each of four successive days. Each bar shows a clear span marking the hours the wall foot is out of the water, and in each lower bar that clear span has shifted later along the day than in the bar above it. day 1 day 2 day 3 day 4

A diagram of the pattern, not a tide table. The clear span is the part of each day the toe of the wall is out of the water, and it arrives later on each successive day.

The weather-window sheet on the front page counts what is left once that movement, the daylight and the days a week is expected to be workable are put together. It is arithmetic on figures a reader types in, and it is a planning aid rather than a forecast.

What access means on a beach

Access on a shoreline is a property of the hour rather than of the site. A shingle bank that carries a tripod at low water is a different surface two hours later, and a ladder footed on wet shingle is not footed at all. The survey records the access used at each observation point for that reason, and the record is written at the point rather than reconstructed afterwards.

Where the only safe reading is from a distance, it is taken from a distance and written as such. A level read across forty metres of beach with a staff held by one person in wind is a usable figure if the distance and the conditions are stated beside it, and a misleading one if they are not.

Planning a visit to an exposed frontage

A visit is planned backwards from the hinge: the one part of the frontage that can be read in the fewest hours of the fortnight. That part is booked first and everything else is arranged around it, because a day spent on the easy two thirds is a day that has to be repeated.

Wind matters more than rain for the instrument and less than rain for the paper. A staff cannot be held still in a strong onshore wind, so a levelling run is moved rather than attempted; a written sheet, on the other hand, survives drizzle and does not survive a shower, which is why the sheets are small and go into a pocket between points.

The practical consequence is that a coastal survey is quoted in windows rather than in days, and the written programme names the windows it depends on. Enquiries are answered at enquiries@aquavail.work, and the useful first line of one is the frontage and the postcode.