Abiotic Systems Flashcards
Soil Series
a group of soils originating from the same parent material and having similar soil horizons in the soil profile, with the primary difference between them being their soil texture. Each soil series is named for a nearby geographic feature (e.g. town name). Soil series are divided into “phases” based upon their difference in texture, and the name of a soil phase indicates a feature that affects management. An example of a soil series and phase name would be “Hagerstown silt loam, 3 to 8 percent slopes.”
Through the USDA, the NRCS (National Resources Conservation Service) provides soil maps to the public that can be used to determine the soil series found at a specific site. If more detailed information (including soil chemistry) is required, the landscape architect can commission a soil survey for a site.
Soil Horizon
a layer parallel to the soil surface whose physical, chemical and biological characteristics differ from the layers above and beneath. Horizons are defined by obvious physical features such as color and texture.
Soil Profile
a vertical section of the soil through all its horizons and extending into the parent material.
Sand
The largest particle size, with soil particles between 0.05 and 2.0 millimeters in diameter
Silt
Fine soil particles between 0.05 and 0.002 millimeter in diameter that can be picked up by air or water and deposited as sediment .
Clay
The smallest particle size, with soil particles smaller than 0.002 millimeters in diameter
Loam
40% sand, 40% silt and 20% clay
Porosity
the void size between particles within a soil and can be expressed as the percentage of void space in a soil.
Well graded soil
a soil with a wide range and even distribution of soil particle sizes, in which the small soil particles fill the voids created by the larger grains.
Gap graded soil
a soil that contains various particle sizes, but in which gradation between sizes is broken by the absence of some particle sizes
Uniformly graded soil
a soil that consists of a single range of particle size.
Permeability
is the rate at which water moves through soil
Infiltration Rate
rate at which water flows into soil through small pores.
Percolation
downward movement of water in a soil
Hydric Soils
characterized by being heavily saturated with water for prolonged periods of time, and this prolonged saturation renders the soils anaerobic and generally results in the soils being bluish in color.
Bearing Capacity
the measure of a soil to decrease in volume under the pressure of a given weight. As such, knowing a soil’s bearing capacity can help determine where a foundation or roads can be constructed, given that soils with poor bearing capacity can lead to structural failures and other safety issues
Angle of repose
the maximum slope at which a loose material can be piled while remaining stable.
Soil elasticity
ability of a soil to return to its original shape after being subjected to a load condition.
Soil Plasticity
ability of a soil to be deformed under pressure without breaking apart
Liquid Limit
minimum moisture content at which a soil will flow under its own weight.
best practices to reduce soil erosion
Preserve existing vegetation
Reduce the total area of land disturbance
Stabilize excavated areas with seeding, sodding, matting or mulching and divert runoff away from these areas
Minimizing disturbance to steep slopes
Schedule clearing and grading activities during the dry season and suspend them prior to and during precipitation events
Locate non-point pollution sources (e.g. construction access roads) in areas that do not drain directly into water bodies
Introduce erosion control fencing, blankets and stabilize drainage channels with erosion-resistant materials (e.g. riprap)
Gully Erosion
widening, deepening, and headcutting of small channels and waterways due to erosion
Rill Erosion
removal of soil by running water with formation of shallow channels that can be smoothed out completely by normal cultivation.
Sheet Erosion
removal of a fairly uniform layer of soil or materials from the land surface by the action of rainfall and runoff water.
NPK Value
the ratio of:
Nitrogen (N)
Phosphorous (P)
Potassium (K)
Nitrogen does
Nitrogen supports plants’ rapid growth and encourages the healthy development of foliage and fruit
Potassium does
helps strengthen plants’ abilities to resist disease and plays an important role in increasing crop yields
Phosphorus does
helps a plant convert other nutrients into usable building blocks with which to grow
Prime soils
these soils require the fewest inputs for productive agriculture. Locations with prime soils require comparatively less irrigation and fewer fertilizers and pesticides than areas without prime soils
Amending soil
When soils are overly acidic, lime should be added. When soils are overly alkaline, sulfur should be added. soils high in salt can be amended through the addition of gypsum.
Topography considered important because
topography is generally considered the most important variable when siting a new project. Topography influences a wide variety of critical issues, including grading, development density, construction costs and the location of roads and other infrastructure. In general, site planning and design should follow or otherwise relate to existing landforms not only to respect context, but also because grading causes significant site disturbance and is costly
Spot Elevations
are highly accurate readings shown for specific points. Often these are areas of importance to the designer (e.g. the finished floor elevation of a structure, the top or bottom of a wall) or to the understanding of a landform (e.g. the high point of a hill, the summit of a mountain). Spot elevations are more accurate than the information provided by contour lines.
Contour lines
are lines on a topographic map that establish the elevation at any point along that line. Contour intervals (the vertical distance between each contour line) will vary according to the accuracy of a map, but the elevational information provided by the contour line is generally considered accurate to one half the contour interval given. For example, if a topographic map provides 2-foot contour intervals, that map would be considered accurate to one foot
Slope ranges
0–3% (nearly level)
3–7% (gently sloping)
7–12% (moderately sloping)
12–25% (strongly sloping)
25–40% (steeply sloping)
40–70% (very steeply sloping)
70+% (extremely sloping)
Slopes aspect
or orientation, is the direction that the slope faces relative to the sun. Aspect is typically described by compass direction (e.g., a northerly aspect) and—along with slope—impacts the amount of solar radiation received at a given location on a site.
Relationship between slope aspect and microclimate
Southern slopes receive the most sun in winter months
Southeastern slopes offer the most desirable microclimates
North-facing slopes are colder than south-facing slopes
Northwestern slopes receive cold winter winds
Western slopes are hottest in the summer
Geology-specific site inventory and analysis
Landforms
Seismic hazards
Depth to bedrock
Why geology matters
the cost of excavating a cubic yard of rock is many times greater than the cost of excavating the same volume of soil.
Karst
landscape underlain by limestone which has been eroded by dissolution, producing ridges, towers, fissures, sinkholes and other characteristic landforms.
Glacial Erratic
a glacially deposited rock (often a large boulder) differing from the type of rock native to the area in which it rests.
Moraine
a mass of rocks and sediment carried down and deposited by a glacier, typically as ridges at its edges or extremity.
Effect of impervious surface
Increased rate and volume of stormwater runoff
Increased frequency and severity of flooding
Reduced water quality
Reduced infiltration and diminished aquifer recharge
Reduced stream flow during dry weather
Ecological degradation
Reduced recreational opportunities on the water
Rational Equation Calculation
Q = ciA
Rational Equation Calculation
Q = the peak discharge measured as cubic feet per second
c = the runoff coefficient (a value between 0 and 1). A measure of how permeable a surface or area is, with this number being a higher value for areas with low infiltration (e.g. pavement, steep slopes), and a lower value for areas with high infiltration (e.g. forest, flat land).
i = rainfall intensity measured as inches per hour
A = drainage area measured in acres
Riparian Zone
the interface between land and a river or stream, and these areas generally provide the following benefits:
Groundwater recharge and discharge
Sediment stabilization
Flood attenuation
Water quality maintenance
Wildlife habitat
Climate moderation
Shoreline protection
First Order Stream
primary drainage ways at the beginning of the hydrological system
Second Order Stream
formed by the confluence of two first-order streams, and this naming convention continues as additional streams come together in a hydrological system.
Ephemeral Stream
a stream that flows only in response to precipitation
Intermittent Stream
a stream that flows only part of the time or through only part of its reach.
Perennial Stream
a stream that flows continuously.
Floodplane: Channel
the portion of the floodplain where a stream/river flows under normal conditions
Floodplane: Floodway
the portion of the floodplain that is used to convey floodwaters during a 100-year flood
Floodplane: Flood Fringe
the portion of the floodplain outside the floodway that does not convey floodwaters and usually contains slow-moving or standing water.
Base flood elevation (BFE
whole-foot elevations of the 100-year floodplain that have been studied in detail at selected intervals. In areas where building has occurred within the 100-year floodplain, BFE calculations are often used to determine the height to which living spaces must be constructed to be safe from a 100-year flood.
Freeboard
any portion of the flood in excess of the base flood elevation (measured in feet).
Floodplane buildings
None are allowed, pick uses that do not require a structure
No FEMA Map, look for:
Topography
Soils
Vegetation types
Extent of past flood flows
Flood hazards mitigated by:
expanding opportunities for stormwater infiltration, minimizing the uses of impervious surfaces, decreasing the volume of runoff during storm events and through restricting development to areas outside of floodplains.
Point Source
any single identifiable source of pollution from which pollutants are discharged (e.g. factory smokestack
Non point source
pollution caused by rainfall or snowmelt moving over and through the ground, during which it absorbs and/or assimilates natural and human-made pollutants and deposits them into lakes, rivers, wetlands, groundwater and the ocean
Sediment can cause:
Decline in water quality
Negative impacts to aquatic vegetation and animals
Negative impacts to aquatic recreation
Unwanted biological growth (e.g. algal blooms)
Increased turbidity
Decreased flow capacity in streams/rivers
Flooding in areas that never or rarely flooded in the past
Sedimentation and Aggradation
As a river curves, erosive forces act against the outer bank of the river (i.e. the curve with the larger radius), carving into it over time and introducing a greater sediment load downstream. Sedimentation can be conceived of as the opposite of erosion, and the inner bank of the river (i.e. the curve with the smaller radius) is where sedimentation occurs. This process of sedimentation is also referred to as aggradation.
Total maximum daily load” (TMDL)
the calculation of the maximum amount of a pollutant allowed to enter a waterbody so that the waterbody will meet and continue to meet water quality standards for that particular pollutant. A TMDL determines a pollutant reduction target and allocates load reductions necessary to the source(s) of the pollutant.
High or Shallow Water Table
can contribute to storm surges and flooding and—although it does not preclude excavation—it does make excavation more expensive given that any structure or foundation below the water table would need to be adequately waterproofed (thereby increasing the project budget). A high water table can also impact on-site stormwater infiltration and the provision of septic systems. Note also that groundwater pumping can lower the water table, thereby negatively impacting hydrological resources.
Aquifers
Groundwater tables are falling as water demand exceeds aquifer recharge rates.
Excessive pumping of aquifer systems can result in land subsidence and related ground failures.
Aquifer recharge areas are particularly important locations to identify and protect from development
Climate is composed of:
Temperature
Humidity
Wind
Precipitation (rain, snow)
Solar Radiation
Albedo
Albedo is the measurement of an object’s reflectivity. Specifically, it measures the fraction of solar energy reflected from a surface back into space. Albedo varies between 0 and 1. Albedo commonly refers to the “whiteness” of a surface, with 0 meaning black and 1 meaning white. Therefore, an asphalt parking lot would have a low albedo (therefore absorbing a great deal of solar energy as heat), whereas a concrete surface painted white would have a high albedo (therefore reflecting much of the solar energy off its surface and not absorbing as much heat as the asphalt)
Angle of Incidence
is the angle at which a ray of light (usually the sun) hits a surface.
Drainage wind
a wind that blows from a higher elevation to a lower elevation
Azimuth
the direction of a celestial object from the observer, expressed as the angular distance from the north or south point of the horizon to the point at which a vertical circle passing through the object intersects with the horizon.
Microclimate
the differences in weather-related phenomena - such as humidity, temperature, rainfall and wind - over a relatively small geographical area. Microclimates are of great importance in the process of site analysis and site design.
Microclimate on site
Southern orientations receive the most sun in winter months
Southeastern orientations offer the most desirable microclimates
North-facing orientations are colder than those facing south
Northwestern orientations receive cold winter winds
Western orientations are hottest in the summer
