Fieldwalking is a tried and tested evaluation technique that involves the surface collection of artefacts from ploughed fields. The aim is to identify areas of former activity on a site by plotting the distribution and concentration of material and assessing it by period. Fieldwalking is particularly effective in circumstances where more physical archaeological evidence is either ephemeral or absent and would not necessarily be detected using other techniques such as geophysical survey or trial trenching.
Studies have shown that despite hundreds, if not thousands of years of ploughing, cultural material moves little from its original location, and the act of ploughing merely brings buried artefacts to the surface. In situations where there might be little other physical evidence such as those associated with prehistoric transient human activity, artefactual material might be the only indicators of habitation sites. Despite being a lesser used technique in commercial archaeology, it is still an extremely efficient and cost-effective technique in these circumstances.
To carry out a fieldwalking survey, a site is normally laid out on a grid pattern with lines spaced about 25m apart and markers set along each line at 20m intervals. Both spacings can vary according to requirements. A fieldwalker walks along each line, usually with a time limit to reach each marker, and collects any artefacts along the line and either side of it. These are bagged and dropped at the line markers before moving along the line to the next marker and repeating the exercise until the line is walked. This is replicated across the grid until all lines have been walked and the field has been sampled. Following quantification and assessment of the finds, the results are often plotted onto maps by computer in order to provide a series of spatial distribution plots of the finds collected in order to identify whether there are any concentrations or types of activity across the site. This process often narrows interest down to specific areas and determines whether any further investigation is required. Where this is needed, further work might take the form of more inensive fieldwalking over the areas of interest or evaluation by test-pitting or machine dug trial trenches. Combined, the results of the evaluation will be included in an illustrated report and accompany a planning application.