Dr Gerry Wait, Director at Nexus Heritage provides an overview of Desk-based Assessments and their importance in early-stage heritage advice.

A Desk-based Assessment (DBA) is usually the first formal opportunity for organisations proposing changes in use or management of land or buildings to benefit from professional heritage advice.

Because of this ‘early stage’ involvement, this can be very important in terms of initial advice.  An initial point to make, without being facetious, is that archaeology, whether of landscapes or buildings is all about the unknown and the unexpected. The excitement on Time Team programmes comes from the discovery –in professional life this is a carefully managed process, but the essential point remains that surprise discoveries are not uncommon. Finding archaeology at the desk-based stage may not always be welcome, but finding archaeology later in the design and construction process gets increasingly expensive and difficult to manage. So the key is to get it ‘right’ at the outset.

Getting the right advice

There are 2 elements to ‘getting it right’ consisting first of getting appropriate professional advice, and second, of getting advice and reports undertaken to the appropriate standards and tailored to a specific development proposal.

Appropriate professional advice can usually be summarised by making sure your advisor is a professional – and that means a member of the UK’s Institute for Archaeologists (IfA), or an equivalent professional institute (there are only a few elsewhere around the world).

IfA membership – look for either full Members or Associates (MIfA or AIfA as post-nominals) means that the individual has been validated, signed up to a code of conduct, undertakes continuing professional development and agreed to work in accordance with appropriate standards.

Alternatively, look for advice from an organisation that is an IfA Registered Organisation – where a MIfA is responsible and the entire organisation adheres to the same professional standards. IfA is the archaeological equivalent of the Royal Institute of British Architects (RIBA) for architects, Institute of Civil Engineers (ICE) for engineers or Royal Institute of Chartered Surveyors (RICS) for surveyors.

Secondly, ensure the work is done to the appropriate standard, in this case the IfA’s Standard and Guidance for historic environment Desk-based Assessment 2012 revision ( http://www.archaeologists.net/sites/default/files/node-files/DBA2012-Working-draft.pdf ). This sets out the expected sources of information that should normally be consulted, and the analysis of those sources, leading to the types of conclusions and recommendations that would normally arise. Be prepared to discuss expectations and risks with a MIfA/RO at the outset, and expect clear advice before commissioning a DBA on what is going to be done and why. Not every source of information will be applicable in every development proposal, but to not consult some sources for reasons of time or cost, introduces increased risks that will need to be documented and taken into consideration in decisions throughout the design and application process.

The HER and DBA

The single most important source of information will be the Historic Environment Record (HER), which all planning authorities are required to have access to. However, after the cut-backs in recent years to local authority funding, not all authorities will have an HER in-house, nor will all have access to heritage professionals to maintain an HER. In addition, getting information out of an HER can sometimes be both costly and sometimes time-consuming (for small projects or enquiries early in the planning process). Early contact should be made with the local planning authority’s archaeological adviser in order to agree the brief for the DBA, and ensure that it will meet the local planning authority requirements. However, some local authorities no longer have archaeological officers, or where officers are still in place they may no longer have the scope to offer advice, which makes the importance of the professional undertaking a DBA and his/her reporting all the more important.

The process of analysis leading to conclusions and recommendations is often an iterative process as well, and should be undertaken with specific reference to both the heritage information about a site and the emerging development scheme. A generic desk-based assessment would be unlikely to be considered ‘professional’ – but there is nonetheless a continuum along which detail and specificity can range. The key to managing this issue rests in the concept of the significance of the known or potential heritage remains – more significant remains are likely to mean greater risks of costs and management down the line – and managing responses and costs begins with getting better information from the outset.

The standard briefly summarised is to determine, as far as is reasonably possible from existing records, the nature, extent and significance of the historic environment within a specified area. DBA will be undertaken using appropriate methods and practices which satisfy the stated aims of the project, and which comply with the Code of conduct, Code of approved practice for the regulation of contractual arrangements in field archaeology, and other relevant by-laws of the IfA. In a development context, DBA will establish the impact of the proposed development on the significance of the historic environment (or will identify the need for further evaluation to do so), and will enable reasoned proposals and decisions to be made whether to mitigate, offset or accept without further intervention that impact.

The purpose of a DBA according to the guidance is to:

  • Gain an understanding of known assets and the potential for heritage assets to survive within the area of study;
  • Of the significance of any such assets considering their archaeological, historic, architectural and artistic interests;
  • Assess the impact of proposed development or other land use changes on the significance of the heritage assets and their settings;
  • Outline strategies for further evaluation whether or not intrusive, where the nature, extent or significance of the resource is not sufficiently well defined and/or develop design strategies to ensure new development makes a positive contribution to the character and local distinctiveness of the historic environment and local place-shaping;
  • Proposals for further archaeological investigation within a programme of research, whether undertaken in response to a threat or not.

Research and experience

Research and interpretation are terms that we need to consider in more detail. And this links back to my initial point about archaeology and discovery. Research and the organisation of data may seem a basic skill, but not all archaeologists have the same or appropriate expertise in conducting research, because research methods, sources, and analysis need to be linked to the likely subject matter on a site.

Even more important is having the appropriate experience and expertise to interpret the results of research. What this really means is being able to recognise and understand the clues that indicate either that known heritage remains may be significant, or that there is a heightened potential for significant remains to present. Good research can be undone by inadequate expertise in interpretation. A good professional will advise when they do not have the appropriate expertise called for in a particular set of circumstances, but the savvy client commissioning a DBA will assure themselves that their consultant is suitably skilled. Having the appropriate expertise means that the client gets the best advice based on the best information at each stage in a process, so that discoveries come as a positive opportunity not as an unwelcome alarm.

DBA contents

A DBA report will normally contain, as a minimum:

  • A non-technical summary;
  • A clear map of study area;
  • A list of the data sources used;
  • A succinct disposition of aims and purpose and methodology employed;
  • Clearly identify the heritage assets and archaeological potential of the study area;
  • Assess the interest and significance of each asset and its setting, focussing on those aspects which will be affected by any proposed or predicted changes;
  • Assess the nature of the effects and options for reducing or mitigating harm;
  • A description of the area’s historic character and the effect of proposed development upon it (where appropriate, this should include options for conserving or enhancing local character);
  • Conclusions, including a confidence rating and the extent to which the aims and purpose have been met and references;
  • Supporting illustrations at appropriate scales, along with supporting data (sometimes tabulated), may be provided in appendices.

The change from the old Planning Policy Guidance Notes 15 and 16 to PPS5, to the NPPF has marked several important shifts. First, the compression of concepts from several hundred pages in the PPGs down to 4-5 pages in the NPPF means that the arguments can appear cryptic and the language coded, so again advice from a MIfA/RO and a planning consultant (a member of RTPI) is good practice.

Second, the issue of the setting of heritage remains has emerged as an important planning consideration – so assets (buildings or sites) located off-site can still be affected by changes in land use or development. This ought to be considered, even if briefly, at DBA stage.

Third, and of possibly greater importance is the shift towards seeking benefits to both developers and local communities from the process of managing impacts to heritage assets. The language used to be all about minimising impacts and managing risk – and these remain important. However, that is not the end of the matter, and developers can expect to have some benefits derive to them from the heritage work they have to undertake through the planning process. Likewise, developers ought to expect that local communities should also benefit from the works – which can take many forms including community engagement in investigations, open days, exhibitions, accessible publications and so on.

Commissioning a good DBA and getting good professional advice sets the appropriate foundations for this process and for a wide range of further investigations and activities that all lead towards the final benefits. But as the old adage has it: If you don’t know where you are going then you probably won’t get there.

Desk-based assessments are almost always done in support of either outline or detailed planning applications – they are essentially pre-planning works. We now need to consider 2 forms of archaeological research/investigation that move us into a grey area. This reveals a great diversity in the application of the seemingly simple heritage policies in NPPF. Local authorities and their archaeological advisors are notably diverse in what they expect in desk-based assessments, and this diversity grows ever greater when the next 2 ‘logical’ steps in the archaeological process are concerned – aerial photographs and geophysical surveys.

Aerial Photographs – the next stage

Aerial Photographs (APs) have been an important archaeological tool for nearly a century. The popular TV programme ‘Time Team’ has revealed AP analysis to the public – the principle being that buried archaeological remains may affect crop growth or soil colours. The patterns of stunted plants in spring fields or green plants in a field turning golden in august all may reveal buried remains. Not all types of archaeology affect crop growth, and not all years are equally good at revealing these effects, so the technique is not a panacea, and the absence of crop-marks does not mean an absence of archaeological remains. In particular, crop-marks work best in revealing relatively shallow buried archaeological sites, and more deeply buried sites (e.g. where rivers flood and silt their floodplains, or at the base of steep hills) are unlikely to be visible. However, the tool remains an important one to the archaeologist.

Many archaeologists have basic skills in recognising crop-marks from aerial photographs, and where this technique may be important, then developer-clients or consulting archaeologists will turn to archaeologists specialising in the technique. The results of many previous aerial surveys have now been incorporated into many HERs through a national enhancement project, the National Mapping Programme, funded by English Heritage.

The ‘geophys’

If ‘Time Team’ has explained aerial photographs, this is nothing compared to the mystique of, and reliance placed upon geophysical surveys – ‘the geophys’. The principles behind geophysics are even more abstrusely scientific than for aerial photographs, but at the simplest level, the operative principle is that the presence of archaeological remains will affect how either minute changes in magnetic pulses or electrical resistance is conducted through the soil. The same limitations apply to geophysics as to APs – deeply buried sites (generally over 6-700mm below the surface) are in general harder to detect, and local geology and even weather (like prolonged heavy rain) can affect results and interpretation.

Ground penetrating radar uses radar to ‘see’ more deeply into the ground or to see small faults in masonry structures and buildings, but is much slower and therefore more expensive to implement. Just as with APs, many archaeologists can ‘read’ many geophysical ‘plots’ and may even have had experience in using the survey technology, but again geophysics is something best undertaken and interpreted by suitably skilled professionals.

Dr Gerry Wait


Nexus Heritage and former Chairman Institute for Archaeologists, Chair of the Registration Committee (Organisations) for the IfA and current Co-Chair of the Committee on Professional Associations in Archaeology for the European Association of Archaeologists

Tel: 0151 326 2247




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