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Hydrologic soil maps describe the infiltration rates for different soil groups across Port Stephens. These maps can be used to evaluate land for planning, development and stormwater management.

Council's Development Control Plan (DCP) requires that stormwater drainage plans and a written description of the proposed drainage system be prepared in accordance with the current Australian Rainfall and Runoff Guidelines using the current hydrologic soil mapping data for Port Stephens.

This map provides an estimation of hydrologic groups of soils according to the four class system and was released by the NSW Government on 11 October 2016. It uses the best available soils mapping coverage and was derived by linking a Hydrologic Group class to a particular Great Soil Group.

Group A

Group A soils have high infiltration rates, even when thoroughly wetted consist primarily of deep well drained sands or gravel. These soils have a high rate of water transmission.

For design purposes, it is assumed that the Antecedent Moisture Condition is "rather wet" (refer to Australian Rainfall and Runoff (ARR) 2016, Table 5.3.11) and the Horton Maximum (Initial) Infiltration Rate is 83.6 mm/hr, the Minimum (Final) Infiltration Rate is 25 mm/hr and the Shape Factor/Decay Rate k is 2 /hour (refer ARR 2016, Table 5.3.12).

Group B

Group B soils have moderate infiltration rates when thoroughly wetted and consisting primarily of deep coarse textures. These soils have a moderate rathe of water transissions.

For design purposes, it is assumed that the Antecedent Moisture Condition is "Rather wet" (refer to ARR 2016, Table 5.3.11) and the Horton Maximum (Initial) Infiltration Rate is 66.3 mm/hr, the Minimum (Final) Infiltration Rate is 13 mm/hr and the Shape Factor/Decay Rate k is 2 /hour (refer ARR 2016, Table 5.3.12)

Group C

Group C  soils have slow infiltration rates when thoroughly wetted and consisting of primarily of soils with a layer that impedes downward movement of water, or soils with a moderately find texture. These soils have a slow rate of transmission.

For design purposes, it is assumed that the Antecedent Moisture Condition is "Rather wet" (refer to ARR 2016, Table 5.3.11) and the Horton Maximum (Initial) Infiltration Rate is 33.7 mm/hr, the Minimum (Final) Infiltration Rate is 6 mm/hr and the Shape Factor/Decay Rate k is 2 /hour (refer ARR 2016, Table 5.3.12).

Group D

Group D soils have very slow infiltration rates when thoroughly wetted and consisting primarily of clay soils with a high swelling potential, soils with a high water table, soils with a clay layer, and shallow soils over nearly impenetrable materials. These soils have a very slow rate of transmission.

For stormwater design purposes, it is assumed that the Antecedent Moisture Condition is "Rather wet" (refer to ARR 2016, Table 5.3.11) and the Horton Maximum (Initial) Infiltration Rate is 33.7 mm/hr, the Minimum (Final) Infiltration Rate is 6 mm/hr and the Shape Factor/Decay Rate k is 2 /hour (refer ARR 2016, Table 5.3.12).

Click here for larger view of Hydrologic Soil map

Click on the map above to view a larger version of the Hydrologic Soil Mapping Index.

View the Hydrologic Soil Mapping via the links below.

Council do not object to a development proponent wishing to undertake geotechnical testing to determine site specific permeability. Given the potential for large variability in test results and their impact on design and performance outcomes, Council require a development proponent to follow a detailed approach.

For additional Infiltration Information, please view our fact sheet:

Contact Details
Development Engineer
Phone: (02) 4988 0255
Email: Development.Engineering@portstephens.nsw.gov.au