Ecological Inventory for Sustainable Land Use Planning
Ecological Inventory for Sustainable Land Use
Environmental inventory involves compiling information about the ecological features of a landscape. This information is crucial for sustainable land use planning and development.
Key Ecological Features
Several factors are considered when conducting an ecological inventory:
- Conservation Value: The productivity of resources like soil for farming.
- Ecological Functions: The significance of land units, such as woodlands that buffer human populations from wildlife-borne diseases.
- Public Health Threats: The degree of risk from hazards, like proximity to earthquake fault lines.
- Ethical and Spiritual Value: The cultural and spiritual significance of the land.
Specific Ecological Features
- Topography and Slopes
- Soils
- Wetlands
- Wildlife Habitats
- Watershed Health
- Natural Hazards
Development Practices and Slope Stability
Two key development practices are considered:
- Siting structures on unstable or potentially unstable slopes. Issues include inadequate slope identification and mapping, and insufficient land use controls.
- Disturbing stable slopes, leading to failure, accelerated erosion, and vegetation deterioration due to inappropriate development practices.
Digital Elevation Models (DEMs) automate slope delineation, replacing manual mapping. DEMs are digital files of terrain elevations and are standard products of the US Geological Survey (USGS). However, slope should not be the only factor in determining ground stability. Other factors include minimal vegetation, cut and fill practices, and soil/bedrock prone to instability under heavy rainfall.
Soil Analysis
Soil analysis is critical for guiding land use decisions. The National Resources Conservation Service (NRCS) of the US Department of Agriculture is responsible for soil survey reports. Factors influencing survey coverage include soil complexity, topography, and user needs.
Key soil features for suitability assessment:
- Weight-bearing capacity
- Shrink/swell potential
- Infiltration capacity
- Erodibility
- Slope
- Depth to seasonal high water table
- Fertility
Weight-bearing capacity refers to a soil’s resistance to compression. Coarse particles (sand and gravel) offer greater stability than fine-grained clay soils.
Shrink/swell describes how much soil contracts and expands with moisture variations. Clay soils are prone to significant changes, impacting foundations and utility lines.
Infiltration capacity is the rate at which water penetrates the soil surface. Clay soils have low infiltration rates, while sand and gravel have high rates.
Erodibility is the susceptibility of soil to runoff. The K-factor represents relative erodibility, influenced by vegetation, soil type, slopes, and rainfall.
Slope is the inclination of the landscape and is related to soil type.
Depth to seasonal high water table is the distance between the soil surface and the upper level of the water table.
Fertility refers to nutrient-rich soils with high organic matter content, supporting agricultural productivity.
Wetland Identification
Wetland identification requires three key features:
- Presence of surface water for a continuous period during the year.
- Presence of saturated soils formed under saturated conditions.
- Presence of vegetation adapted to wet soils.
Five broad classes of wetland systems exist:
- Marine (deep water)
- Estuarine (shallow saltwater zone)
- Riverine (freshwater stream channels)
- Lacustrine (standing water bodies like lakes)
- Palustrine (inland marshes, swamps, and bogs)
Biodiversity Assessment
Biodiversity assessment considers the complexity and variability of plant and animal species and their ecosystems.
Composition: The identity and abundance of species and habitat types.
Structure: The horizontal and vertical distribution of vegetation.
Function: The processes that generate and maintain biodiversity.