The steepest angle at which loose material remains stationary without sliding down slope
Angle of Repose
Survey that locates all physical improvements on the land in relation to the boundary lines of the land
As-built survey
Original survey, resurvey, or retracement of public lands within the public land survey system of the United States for restoration of property lines
Cadastral Survey
Largest nonpoint water pollutant by volume
Sediment
5 contributing factors of soil erosoion
- Soil type
- Vegetative cover
- Topography
- Climate / Precipitation
- Wind
Erodibility of soils determined by (4) physical properties of the soil:
- Particle size and gradation
- Soil structure
- Permeability
- Organic content
Highly erodible soils
High content of silt
Fine Sand
Less erodible soils
Well-graded gravels and sand-gravels
Clayey soils (but clay that does erode will remain suspended, not ideal)
Soils w/ organic content
Model for estimating soil loss
Universal Soil Loss Equation (USLE)
Revised Universal Soil Loss Equation
RUSLE
How vegetation helps to prevent soil erosion (3)
- Shields soil from impact of rain
- Slows runoff velocity through increased surface friction
- Root systems hold soil in place
Ways to reduce erosion caused by topographic conditions (4)
- Avoid steep slopes
- Limit gradient and length of slope
- Protect disturbed slopes as quickly as possible
- Consider how orientation will impact ability of vegetation to recover
Construction scheduling and erosion (2 issues)
- Construction should take place during relative dry periods (when possible)
- Construction schedule should be timed with optimal seeding period(s)
Detachment and movement of soil or rock fragments by water, wind, ice, and gravity
Erosion
The process of settling or being deposited as sediment
Sedimentation
Erosion and Sediment Control Principles in construction (4)
- Minimize disturbance
- Control runoff
- Collect sediment
- Monitor construction
(5) Principals of minimizing construction disturbance
- Work with existing topography and preserve pre-development drainage patterns
- Restrict area of disturbance
- Cluster development
- Manage site construction (equipment movement and staging; thoughtful sequencing and phasing)
- Preserve existing vegetation, particularly woodlands
(2) Methods of controlling runoff on construction sites
- Divert stormwater to prevent runoff from crossing disturbed / exposed soils
- Vegetative buffer strips (reduce runoff velocity) - if diversion is not feasible
(5) Methods of collecting sediment on construction sites
- Sediment traps / basins*
- Inlet protection
- Silt fences / barriers
- Vegetative filter strips
- Stabilized construction access points
- only sediment basins are suitable for substantial / concentrated flows
Erosion Control: Runoff Control Measures (5)
- Diversions
- Waterways (natural / constructed channels to dispose of excess water)
- Slope protection structures (pipes / chutes that direct water down steep slopes)
- Grade control structures (chutes, weirs, pipe drop spillways)
- Outlet protection
Erosion Control: Soil Stabilization Measures (5)
(Generally: Protect soil surface from impact of raindrops and of sheet or rill erosion)
- Divert flow
- Vegetation
- Retain ex. topsoil for reuse
- Reestablish vegetative cover asap
- Organic / inorganic mulch, gravel, structures stone, geotextile
Erosion Control - Biotechnical Measures:
Good for small slumps that are frequently wet. Live rootable cuttings tamped into ground; create a stabilizing mat as roots grow; removes excess soil moisture through uptake
Live Staking
Erosion Control - Biotechnical Measures:
Bundled branch cuttings; align branch and rooting ends; Helps to stabilize slopes, reduce erosion, and reduce face sliding; Placed in trenches parallel to the contour; anchored w/ live and dead stakes
Live Fascines
Erosion Control - Biotechnical Measures:
Similar to live fascine but oriented perpendicular to the slope; More effective than live fascine for earth reinforcement and mass stability; Live branch cuttings layered in criss-cross perpendicular to the slope on excavated benches; then covered w/ soil
Brush Layering
Erosion Control - Biotechnical Measures:
Brush layering w/ added live staking; Best for small, localized holes or slumps
Branch Packing
