5 Conclusions

5.1 Advantages of the survey methodology

The survey methodology, using two epochs of aerial photographs supplemented by historic mapping and parish boundary data, allowed surface-visible palaeochannels to be recorded over a total survey area of 677km², by one researcher in a period of six months. These relatively low time and cost implications, and the ready availability of comprehensive aerial photograph collections in local government archives, enhance the generic potential of the methodology. The resulting GIS dataset is portable and resilient, combining spatial and textual information, and the ArcView platform is compliant with most local SMR systems.

5.2 Undated channels: problems and potential

Most channels within the database remain undated. This is inevitable given the prevalence of cropmark features, the origin of many palaeochannels before the advent of historic maps, and the absence of smaller channel-shifting episodes from the documentary record. Secure dating can only proceed through a programme of coring and analysis, and there is scope within the database for the addition of future findings. The lack of a secure chronology does not, however, detract from the value of the database. A parallel can be drawn with the National Mapping Programme, instigated by English Heritage during the 1980s to map archaeological cropmarks in major gravel-terrace river valleys. This programme produced a huge database of largely undated cropmarks, incorporated during the last ten years into the cultural resource management framework at local government level. This has enabled curators to map archaeological potential more extensively, and to ensure adequate mitigation in the event of development; indeed some undated cropmark complexes have been protected under Scheduled Ancient Monument legislation. In the same way, the catchment-scale mapping of palaeochannels allows areas of palaeoenvironmental importance to be identified (the confluence zones of the upper middle Trent are obvious candidates), and a more appropriate level of mitigation to be applied when the resource comes under threat.

5.3 Further work

The palaeochannel database has therefore placed an important body of data within the cultural resource management framework for the first time. In addition to this cultural resource management role, the current database forms, in the Trent Valley, the first phase of the 'task list' outlined by Howard and Macklin (1999, 538). It should be supplemented by a dating programme, assessment of the preservation and palaeoenvironmental potential of channels, and other prospection methods, such as airborne LiDAR (Charlton et al. 2003; Challis in prep.) and mapping of sub-surface topography in deep alluvium by borehole analysis, test-pitting and augering. This would allow a combination of archaeological and geomorphological data to produce detailed and comprehensive mapping of archaeological and palaeoenvironmental potential, leading to a greater understanding of the interactions between human communities and their landscapes in the Trent Valley.