Post #6: The Treasure Hunt Part II: Physical Conditions Survey

Kevin Caldwell
Post #6:  The Treasure Hunt Part II:  Physical Conditions Survey
This is installment #5 for ecological, site-specific considerations for siting Green Built structures on undeveloped, forested land.   This post highlights physical characteristics of the land that are essential to understand for a truly ecologically based structure.
Landforms:  The overall terrain of the land is a primary consideration.  Do access and potential homesites sit on or near floodplains, at mid-slope or ridgeline positions?  For example, construction on “colluvial fans” – apparently ideal mounds of soil and rock that have eroded from coves above them over geologic time – may be subject to landslides!  Such are actually moving slowly down slope, cracking foundations or even sliding entirely…and they may be subject to future landslides from above. Alluvial floodplains are subject to period flooding.  Curiously, small stream floodplains are often not recognized by site planners or insurance companies.  Alluvial zones (often part of dynamic wetland mosaics over time) rarely perk for septic as they are often too wet.
Aspect:  South-facing is usually the desired aspect for green-built structures though west, east, or north-facing aspects may work for solar gain depending on the landform shape.  In our area, south-facing and low ridgelines generally harbor relatively low wildflower & fern diversity though rare species may actually occur. Northerly and east facing aspects are often the most water retentive, lush, and biodiverse, so road and homesite impacts in these areas can be huge.
Slope: The steepness of land.  This is a primary factor for homesite location and ecological considerations.  Obviously, steeper slopes mean more expensive excavation.   Some counties have slope ordinances while others do not, however anything exceeding approximately 25% – ecologically – should not be excavated due to erosion control issues.
Water: Seeps, streams, and small wetlands are critical resources that must be protected at all costs and these are technically regulated by the US Army Corps of engineers and the NC Division of Water Quality.  Springs and seeps can offer year-round permanent water sources in lieu of wells, and streams and wetlands are critical for wildlife passage and drinking water.  Erosion control efforts must keep road and homesite runoff sediments out of streams.
Soils & Geology:  Soil and its parent material, bedrock, are typically viewed something to be excavated and removed, to our or future generations loss.  However – soils are THE basis for all vegetation systems and thus, wildlife habitat.  Soil “types” are recognized as structurally distinct, and the rarer types or those which are of agricultural importance should be considered, protected, and “recycled” within construction plans.
We’ve now looked at examples the living (botanical, wildlife, natural community) and physical features that we will encounter on a tract of undeveloped land which, for a truly ecologically sited structure, must be considered and protected to the fullest extent. In Blog #7 we’ll review a map of these types of features and talk about making a site plan based on these valuable resources.