LARE Section 2_2 Flashcards
Bearing capacity
the measure of a soil to decrease in volume under the pressure of a given weigh
Angle of repose
the maximum slope at which a loose material can be piled while remaining stable
What type of natural disaster results in hydrophobic soils?
wildfire
What is aggradation
the filling in of stream channel with sediment
What are some ways to reduce soil erosion?
- Preserve existing vegetation
- Reduce the total area of land
- Stabilize excavated areas with seeding, sodding, matting or mulching and divert runoff from these areas
- Minimize disturbance to steep slopes
- Schedule clearing and grading activities during the dry season and suspend them prior to and during precipitation events
- Introduce erosion control fencing , blankets, and stabilize drainage channels with erosion-resistant materials
-Locate non-point pollution sources (e.g. construction access roads) in areas that do not drain directly into water bodies
Gully erosion
the widening, deepening, and head cutting of small channels and waterways due to erosion
Rill erosion
the removal of soil by running water with formation of shallow channels
Sheet erosion
the removal of a fairly uniform layer of soil or materials from the land surface by rainfall or runoff
Geomorphology
the study of the physical features of the surface of the earth and their relation to its geological structures
What data does a geologic map generally include?
the age and distribution of rock layers and the attributes of these rock layers. Map data will also identify locations that are susceptible to earthquakes and landslides, and they will identify seismic fault lines
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 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
Channelization
turning hydrological resources into highly engineered, enclosed and impervious storm drain systems
Time of concentration
refers to the amount of time needed for water to flow from the most remote point in a watershed to the watershed outlet.
Does infiltration increase or decrease with slope?
Infiltration is reduced as slope increases regardless of whether the surface of that slope is impervious or not
What does the Rational Equation Calculation determine?
the rate of runoff
What does Q=ciA refer determine?
the rate of runoff
What does Q stand for in Q=ciA?
the peak discharge measured as cubic feet per second
What does c stand for in Q=ciA?
the runoff coefficient (between 0 and 1). A measure of how permeable a surface is, with this number being higher value for areas with low infiltration, and lower value for areas with high infiltration
What does i stand for in Q=ciA?
rainfall intensity as inches per hour
What does A stand for in Q=ciA?
drainage area in acres
What is a riparian zone?
A riparian zone or riparian is the interface between land and a river or steam
What are some benefits provided by riparian zones?
Groundwater recharge and discharge
Sediment stabilization
Flood attenuation
Water quality maintenance
Wildlife Habitat
Climate moderation
Shoreline protection
What are first order streams?
primary drainange ways at the beginning of a hydrological system
What are second-order streams?
streams formed by the confluence of two first-order streams (naming continues until additional streams come together in a hydrological system)
What is an ephemeral stream?
a stream that flows only in response to precipitation
What is an intermittent stream?
A stream that flows only part of the time or through only part of its reach
What is a perennial stream?
a stream that flows continuously
What is a floodplain?
an area of land adjoining a body of water that has been or may be covered by flood water.
What does a 100-year floodplain mean?
an area of land that has a 1% chance to flood in any given area or will flood once every century on average
What three components are floodplains composed of?
Channel, floodway, and flood fringe
What is a channel?
the portion of the floodplain where a stream/river flows under normal conditions
What is a floodway?
the portion of the floodplain that is used to convey floodwaters during a 100-year flood
What is a flood-fringe?
the portion of the floodplain outside the floodway that doesn’t not convey floodwaters and usually contains standing or slow-moving water.
What is 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 calcs are often used to determine the heigh 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 elevation
What types of maps commonly document floodplains?
FEMA Flood Insurance Maps
How can flood hazards be mitigated?
-expanding opportunities for stormwater infiltration
-minimizing the uses of impervious surfaces
- decreasing the volume of runoff during storm events
-restricting development to areas outside the floodplain
What is point-source pollution?
any single identifiable source of pollution from which pollutants are discharged (e.g. factory smokestack)
What is non-point source pollution?
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, wetland, groundwater and ocean.
What are some negatives of sedimentation in waterways?
Decline in water quality
Negative impacts to aquatic vegetation and animals
Negative impacts to aquatic recreation
Unwanted biological growth
Increased turbidity
Decreased flow capacity in streams/rivers
Flooding in areas that never or rarely flooded in the past
What is sedimentation/aggradation?
can be thought of as the opposite of erosion- sediment is deposited. Especially in the inner radius of the river banks as water flows.
What are some factors that can cause groundwater levels to fall?
When water demand exceeds aquifer recharge rates
Groundwater pumping
What are some results of excessive pumping of aquifer systems?
Land subsidence and related ground failures
What is the mapping resource landscape architects often consult to determine how climate interfaces with plant selection?
USDA Plant Hardiness Zone Map
Albedo
the measurement of an object’s reflectivity, it measures the fraction of solar energy reflected from the surface back into space
How is albedo measured?
between 0-1, with 1 being white and 0 being black (measuring the whiteness of a surface)
Angle of incidence
the angle at which a ray of light hits a surface
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
Drainage wind?
a wind that blows from a higher elevation to a lower elevation
What can a drainage wind cause?
Can cause dryer climates
Can lower temperatures- destroy crops
Lower air temperature
Worse air quality
Which orientation receives the most sun in winter months?
southeastern
Carrying capacity
a measure of the type and density of development that can be supported without detrimental effects to society, the economy, or the environment and without decreasing the capacity of the environment to sustain these uses into the future.
Ecological footprint
is the impact of a person/community or use on the environment, expressed as the amount of land required to sustain their use of natural resources.
xerophytes
plants that require little moisture to survive and are often referred to as “drought tolerant”.
Mesophytes
plants that are adapted to neither dry nor wet environments and grow best with a moderate use of water.
Hydrophytes
plants that are adapted to living in aquatic or in wetland conditions with a surplus of available water.