Erosion and Sediment Control: Terms, Definitions, and Measures, Quizzes of Land Development

Download Erosion and Sediment Control: Terms, Definitions, and Measures and more Quizzes Land Development in PDF only on Docsity! TERM 1 Sedimentation DEFINITION 1 Depostion of soil particles-Caused by wind, rain, ice, and gravity-Erosion rates directly correspond to % of bare soil TERM 2 Potential Problems from Construction Activities DEFINITION 2 -Degradation to downstream properties and waterways- Damage to new and existing infrastrucure-Nuisances: -Dust - Mud on streets TERM 3 When E&SC Plan Needed? DEFINITION 3 -Land disturbing activities >= 10,000 ft^2 (or as low as 2500 ft^2)-Disturbance >1 acre required a VPDES (Virginia Pollutant Discharge & Elimination System) Permit TERM 4 E&SC Plan DEFINITION 4 Plan:-Shows location and size of various E&SC practices- Phase I: Initial clearing and grading-Phase II: Finish grading and protection of infrastructure TERM 5 E&SC Narrative DEFINITION 5 -Provides supporting calcs-Includes info often redundant to Feasability Report(vicinity map, neighboring properties, soil types, critical areas of concern) TERM 6 Factors Influencing Erosion DEFINITION 6 -Rainfall intensity and distribution-Soil properties (permeability/ cohesiveness)-Topography**-Vegetation (surface cover)****Can be controlled to some degree TERM 7 Controllable Design Factors - Topography DEFINITION 7 Avoid critical slope gradients when practically possible:-0-7% slope, 300'-7-15% slope, 150'->15% slope, 75;Limit denuded areas by staging and immediate seeding TERM 8 E&SC Measures - Filtering DEFINITION 8 -Silt Fence-Straw Bales-Inlet Protection (IP) TERM 9 E&SC Measures - Prevention DEFINITION 9 -Construction Entrance (CE)-Slope Drains-Outlet Protection (OP)-Check Dams-Level Spreaders-Seeding (TS/PS) TERM 10 E&SC Measures - Collection DEFINITION 10 -Diversion Dikes-Sediment Traps-Sediment Basins TERM 21 Sediment Basin DEFINITION 21 Drainage area = 3-100 acresInitial storage volume of 134 cy/ac-67 cy wet, permanent storage-67 cy dry, drawdown storage-Principal spillway designed for 25 yr return frequency storm-Often dredged and converted to permanent SWM facilities-Collection TERM 22 Hydrograph DEFINITION 22 Discharge vs. TimeDef'n: A hydrograph is a graph showing the rate of flow versus time past a specific point in a river, or other channel or conduit carrying flow. TERM 23 Hyetograph DEFINITION 23 Rainfall intensity vs TimeDefinition: A hyetograph is a graphical representation of the distribution of rainfall over time. For example, in the 24-hour rainfall distributions as developed by the Soil Conservation Service, rainfall intensity progressively increases until it reaches a maximum and then gradually decreases. TERM 24 Return Frequency and Exceedance Probability DEFINITION 24 Tr = Return FrequencyP = Exceedance ProbabilityP = 1/Tr TERM 25 Rational Method DEFINITION 25 -Used for drainage basins <200 acres-Only computes peak discharge, NOT a full hydrographQ = CiA TERM 26 NRCS TR-55 DEFINITION 26 -Can be used to compute a full hydrograph-Used for detention basin size estimation TERM 27 Area-Weighting the C Coefficient DEFINITION 27 Cw = (Sum CiAi) / A TERM 28 Time of Concentration, Tc DEFINITION 28 Time it takes the most hydraulically remote point in a watershed to contribute runoff to the point of analysis-Q and Tc are inverse