Fluvial Design Guide - Chapter 5

Landscape and heritage

5.6 Common heritage techniques explained

This section explains important heritage techniques and reporting procedures that may be encountered in the design and construction of a fluvial scheme.

5.6.1 Desk study

This is a frequently used term for many professions. The UK has extensive historical map records and archives of land use dating back centuries. These resources should form the basis of  research combined with reference to national and regional resources such as the county archive and the sites and monuments record (SMR).

A desk study can quickly and cheaply define the known heritage value of a site and the likelihood of unknown assets being found.

5.6.2 Rapid field surveys and geophysical investigation

Most commonly used to assess the likelihood of archaeological assets being found, these techniques are non-intrusive as they do not disturb the ground. An experienced archaeologist armed with good desk study maps can walk over an undeveloped area and recognise changes in ground conditions and levels that the untrained eye would not appreciate. A geophysical survey takes this technique one stage further by using ground-penetrating radar to assess the difference in magnetic fields between previously disturbed and undisturbed ground profiles (see Figure 5.14). Both these techniques are relatively cheap compared with exploratory digs and can guide more expensive excavation works to the most important areas.

Figure 5.14 Geophysical survey

This geophysical plot shows the presence of a British-Romano settlement that was investigated as part of the Banbury flood alleviation scheme.

This area was then discounted as an area for potential excavation to win earth material for a proposed floodbank on the grounds of the added cost for investigating and recording the archaeological features.

The four white areas in the centre of the survey are WW2 anti-aircraft gun emplacements that are also of high heritage value. This illustrates the need to consider more recent heritage as well as older artefacts.

 

5.6.3 Evaluation survey

Where unknown archaeological assets are suspected, a small limited archaeological dig can be undertaken to ascertain if there is an asset worthy of full investigation. These evaluation digs save the wasted cost of exploration of a whole site that turns out to have little or no heritage value. Typically 5% of an area of likely archaeological significance is evaluated.

5.6.4 Record or exploration survey

Where there is a need to understand and record the value of a heritage feature, a full exploration survey is required. Such a survey records the character of the asset for future study, sets constraints for construction in its vicinity, or allows for unavoidable damage or wholesale destruction to take place in the knowledge that a full record has been made of the feature.

5.6.5 Watching brief

Where archaeological assets are suspected but have not warranted a full record survey, a watching brief can be put in place. This is when an archaeologist observes the opening of the ground and excavation through parts of the soil profile they suspect might contain archaeological assets. The archaeologist will halt works to investigate any features of note to assess if the area requires further investigation. There is a higher risk of delays to a main construction programme and resulting cost implications if finds are made during the construction period.

5.6.6 Archival report

Such a report should be written after the completion of every piece of heritage survey that captures knowledge about the site. Such reports are forwarded to regional and national archives to allow future interrogation by other heritage professionals as they compile studies in the area or on specific topics.
 


5.6.7 Managing archaeological issues on a project

The Environment Agency’s National Environmental Assessment Service (NEAS) has developed a specific approach aimed at separating archaeological risk from the construction phase of projects, including the consideration of archaeology in most geotechnical investigations.

This approach presumes a preference, in many cases, for pre-construction evaluation and excavation, rather than a watching brief. Watching briefs are increasingly viewed as a high-risk strategy to managing archaeological issues, moving the potential discovery of unknown sites into the construction phase of projects.

On larger schemes, the Environment Agency typically follows this list of activities with regard to managing archaeological risk:

  • discussion with an experienced archaeologist about the project;
  • desk-based assessment;
  • archaeological assessment during geotechnical investigation;
  • geophysical survey;
  • design input to avoid known sites in the design phase of any works;
  • archaeological evaluation to assess survival on the ground (or under it);
  • further design input during the construction planning stage – to avoid locating borrow pits, haul routes, site compounds and other temporary works on sites of known archaeological interest;
  • archaeological excavation of sites at risk (if necessary);
  • defined observation (watching brief) of unexcavated areas that carry some archaeological interest, during the construction phase;
  • public engagement by showing people what has been found and deduced;
  • publication to county and national archives.


5.6.8 Secondary issues associated with heritage matters

Figures 5.15 to 5.20 demonstrate a range of issues that may not at first be considered, but which can influence the preparation of construction proposals.

Figure 5.15 Value of desk-top research

Interrogation of historical data and early editions of OS maps by an experienced practitioner will identify potential areas of archaeological interest.

They can also identify other information that could influence construction such as spring points, rubbish tips, made ground and changes in the course of a river.

This particular historical map allowed the identification of civil war defences at Hereford, that were subsequently investigated by excavation

This illustration and the photographs below were provided by Ed Wilson, archaeologist and NEAS officer, Environment Agency.

Figure 5.16 Setting of historical features

Additional value and interest is placed on the setting of historical features such as bridges, weirs, docks and riverside heritage buildings.

Whether they are designated heritage features or not, local planning authorities and statutory consultees pay particularly close attention to works in the vicinity of heritage features because there is an increased chance of disturbing assets or reducing the visual appeal of the feature itself, reducing the quality of the surrounding setting.
 

Listed bridge in Hereford

Figure 5.17 Major construction activity

Archaeology is at times a major construction activity and it has to be managed as such. It is subject to CDM Regulations, as is any other construction activity, and its risks need to be assessed properly.

This photograph shows the different levels of archaeological exploration required to investigate civil war defence structures, as part of advance works for the Hereford flood alleviation scheme.

Enough time and budget must be made available in construction programmes to conduct the required works, ideally in advance of main construction contracts.

Figure 5.18 Environmental impacts

Archaeological excavation can lead to adverse environmental impacts, including the severing of tree roots as illustrated in this photograph of advance archaeological works undertaken as part of the Hereford flood alleviation scheme.

A balance has to be struck between the need to understand a site’s heritage assets and compromising its visual amenity by potentially killing trees.

The potential environmental impacts of archaeological works may need to be assessed in advance by environmental impact assessment methods.

Figure 5.19 Contaminated ground

Archaeological works often encounter historical rubbish tips and waste areas.

The photograph illustrates excavation of a medieval rubbish pit in Hereford. Whether contamination is historic or contemporary is of limited importance when it needs to be contained and remediated.

Working in proximity to churchyards may also yield human remains that need to be reported to the police and the local coroner.

Figure 5.20 Public safety

Archaeological sites are features of interest to members of the public, particularly if the excavation is in advance of the main works or in a busy public area. This interest must be anticipated, with the control of public access and public safety being of paramount importance, to avoid injuries occurring.

This photograph shows 2m high temporary fencing, with warning signs and ground protection mats, for archaeological works associated with the Hereford flood alleviation scheme.

 

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