Stormwater Management Report · MCU19/0008

Best Practice Erosion And Sediment Control                                       Erosion Hazard Assessment Form



                      Table 3 – Typical properties of various soil groups [1]
   Soil Groups                                             Typical properties [2]
     GW, GP                   Low erodibility potential.
     GM, GC                   Low to medium erodibility potential.
                              May create turbid runoff if disturbed as a result of the release of silt
                               and clay particles.
      SW, SP                  Low to medium erodibility potential.
      SM, SC                  Medium erodibility potential.
                              May create turbid runoff if disturbed as a result of the release of silt
                               and clay particles.
      MH, CH                  Highly variable (low to high) erodibility potential.
                              Will generally create turbid runoff if disturbed.
      ML, CL                  High erodibility potential.
                              Tendency to be dispersive.
                              May create some turbidity in runoff if disturbed.
Note: [1]       After Soil Services & NSW DLWC (1998).
      [2]       Any soil can represent a high erosion risk if the binding clays or silts are unstable.

Table 4 provides general guidelines on the suitability of various soil groups to various
engineering applications.

      Table 4 – Engineering suitability based on Unified Soil Classification [1]
                                            Embankments
                               USC                                        Fill         Slope        Untreated
Unified Soil Class                        Water             Non
                              Group                                                   stability      roads
                                        retaining          water
                                                         retaining
Well graded gravels            GW       Unsuitable        Excellent    Excellent      Excellent          Average
Poorly graded gravel           GP       Unsuitable        Average      Excellent       Average       Unsuitable
Silty gravels                  GM       Unsuitable        Average         Good         Average           Average
Clayey gravels                 GC        Suitable         Average         Good         Average       Excellent
Well graded sands              SW       Unsuitable        Excellent    Excellent      Excellent          Average
Poorly graded sands            SP       Unsuitable        Average         Good         Average       Unsuitable
                                                   [2]
Silty sands                    SM       Suitable          Average        Average       Average            Poor
Clayey sands                   SC        Suitable         Average        Average       Average            Good
Inorganic silts                ML       Unsuitable          Poor         Average        Poor         Unsuitable
Inorganic clays                CL       Suitable [2]       Good          Average        Good              Poor
Organic silts                  OL       Unsuitable       Unsuitable       Poor        Unsuitable     Unsuitable
Inorganic silts                MH       Unsuitable          Poor          Poor          Poor         Unsuitable
                                                   [2]
Inorganic clays                CH       Suitable          Average     Unsuitable       Average       Unsuitable
Organic clays                  OH       Unsuitable       Unsuitable   Unsuitable      Unsuitable     Unsuitable
Highly organic soils           Pt       Unsuitable       Unsuitable   Unsuitable      Unsuitable     Unsuitable
Notes:   [1]      Modified from Hazelton & Murphy (1992)
         [2]      Suitable only after modifications to soil such as compaction and/or erosion protection




IECA (Australasia)                                       November 2008                                       Page 4