Statistical Landscape Sensitivity Applications
For most Phase I archaeological surveys, a research design is constructed where only certain portions of a project area are evaluated through subsurface testing, a process known as "sample stratification". Within these areas, subsurface tests are typically spaced at regular or systematic intervals, either 50 feet or 15 meters depending on the units of measurement used in the overall development project. Thus the resulting percentage of ground area tested for a project during the early phases of the archaeological sequence is typically quite small. The practical purpose of the stratified-systematic sample fraction lies in budgetary and time constraints which prohibit the excavation of entire project areas. The theoretical justification for the stratified-systematic approach is two-fold, with sites statistically shown to be distributed non-randomly in relation to the landscape and its variable components, as well as the likelihood of successfully identifying potentially significant sites through testing at reasonably spaced intervals. Finally, only those portions of a project property slated for development are evaluated, with the stratification process eliminating areas outside the strict limits of the development.
The stratification of sample frames for evaluating the potential presence of prehistoric sites has been shown to be successfully accomplished when taking into account the distribution of certain aspects of the landscape which were most relevant to the occupational and resource procurement logistics of aboriginal populations predominantly engaged in a hunting-gathering economy. Landscape aspects found to be statistically relevant to the distribution of previously recorded prehistoric sites include geomorphological setting, soil texture and drainage qualities, distance to water, type of nearest water source, and drainage or stream rank. Whereas most cultural resource management firms employ a judgmental approach to this stratification, ACS has constructed a preliminary statistical prehistoric landscape sensitivity model for eastern Connecticut based on the distribution of previously recorded sites, a model which will eventually be expanded to include the entire Northeast United States. The stratification of sample frames for evaluating the potential presence of historic sites is based on physical environmental factors as well as more readily researched historic social factors such as early road networks, economic clusters, political boundaries, and other aspects documented in a variety of sources such as historic maps, land records, and other archival sources.
The stratification of a sample frame that results in an efficient testing pattern for the identification of prehistoric and historic sites appropriately requires an extensive amount of background research. The same process may sometimes result in a research design requiring little to no subsurface testing based on prohibitive natural environmental conditions such as extremely rocky soils and/or steep slopes, or modern cultural alterations to the landscape which have eradicated any possibility of preserved sites remaining within a project area. The anticipation of this possibility will sometimes result in the division of a Phase I survey into two components - a Phase Ia assessment survey which is limited to background research and an on-site inspection of environmental conditions; and a Phase Ib reconnaissance survey only in the event that the assessment survey includes a recommendation for subsurface field testing. The following list of projects includes those for which a highly stratified sample frame was employed, relying partly on the prehistoric landscape sensitivity model, and resulting in the successful identification of existing sites within project areas while maximizing cost-efficiency.
Modelling: Prehistoric Site Location Sensitivity
- Targeting Specific Landforms and Ecological Settings: Troutbrook Valley -
- Employing Historic Maps, Land Records, and Genealogical Information: The Preserve -
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