S25-107-Stormwater Report

Best Practice Erosion And Sediment Control                               Erosion Hazard Assessment Form


        The left-hand-side of the table provides an indication of the type of sediment
        basin that will be required (Type C, F or D). The right-hand-side of the table
        provides an indication of the likely erodibility of the soil based on the Revised
        Universal Soil Loss Equation (RUSLE) K-factor.

        Table 3 provides some general comments on the erosion potential of the various
        soil groups.

                          Table 1 – Score if soil K-factor is known
                                                RUSLE soil erodibility K-factor
                           K < 0.02             0.02<K<0.04          0.04<K<0.06              K > 0.06
     Score                       0                   1                      2                     3

                      Table 2 – Statistical analysis of NSW soil data [1]

Unified          Likely sediment basin                    Probable soil erodibility K-factor (%) [2]
  Soil             classification (%)
 Class         Dry                   Wet            Low         Moderate           High          Very High
System
             Type C      Type F        Type D     K < 0.02     0.02<K<0.04      0.04<K<0.06       K > 0.06
  GM            30          58             12        12             51              26                 12
  GC            42          33             25        13             71              17                 0
  SW            40          48             12        49             39              12                 0
   SP           53          32             15        76             18               5                 1
  SM            21          67             12        26             48              25                 1
   SC           26          50             24        16             64              18                 2
  ML            5           63             32        4              35              45                 16
   CL           9           51             39        12             56              19                 13
   OL           2           80             18        34             61               5                 1
  MH            12          41             48        15             19              41                 25
  CH            5           44             51        39             43              11                 7
Notes: [1]    Analysis of soil data presented in Landcom (2004).
       [2]    Soil erodibility based on Revised Universal Soil Loss Equation (RUSLE) K-factor.

Unified Soil Classification System (USCS)
GW      Well graded gravels, gravel-sand mixtures, little or no fines
GP      Poorly graded gravels, gravel-sand mixture, little or no fines
GM      Silty gravels, poorly graded gravel-sand-silt mixtures
GC      Clayey gravels, poorly graded gravel-sand-clay mixtures
SW      Well graded sands, gravelly sands, little or no fines
SP      Poorly graded sands, gravelly sands, little or no fines
SM      Silty sands, poorly graded sand-silt mixtures
SC      Clayey sands, poorly graded sand-clay mixtures
ML      Inorganic silts & very fine sands, rock flour, silty or clayey fine sands with slight plasticity
CL      Inorganic clays, low–medium plasticity, gravelly clays, sandy clays, silty clays, lean clays
OL      Organic silts and organic silt-clays of low plasticity
MH      Inorganic silts, micaceous or diatomaceous fine sandy or silty soils, elastic silts
CH      Inorganic clays of high plasticity, fat clays
OH      Organic clays of medium to high plasticity




IECA (Australasia)                                November 2008                                        Page 3