Reference Document - Coastal Hazard Assessment - MCU24 0094 · MCU24/0094

                                33 Ross Crescent, Sunshine Beach – Coastal Hazzard Assessment | 33 Ross Crescent Family Trust



6.         Erosion Prone Area
The erosion prone area identifies land that may be vulnerable to coastal erosion or tidal inundation over a
100-year planning period and are declared under section 70 of the Coastal Protection and Management
Act 1995.

The ‘Coastal Hazards Technical Guide’ (Department of Environment and Heritage Protection, 2013)
provides guidance on the calculation of an erosion prone area. The erosion prone area width is based on
the following:

      •   short-term erosion from extreme storm events (e.g., a tropical cyclone);
      •   a dune scarp component to accommodate slumping of the erosion scarp following short-term
          erosion;
      •   long-term erosion associated with a deficit in sediment supply;
      •   shoreline recession due to sea level rise; and
      •   a 40% safety factor.

The Erosion prone area is calculated using the following equation:

  =       ×   +   +    × 1+      +

Where:
 =         Erosion Prone Area width (m)
 =         planning period (years)
 =         rate of long-term erosion (m/year)
 =         short-term erosion from the design storm event (m)
 =         recession due to sea level rise (m)
 =         factor of safety (0.4)
 =         Dune scarp component to allow for slumping of the erosion scarp (m)

6.1.      Erosion Prone Area Assumptions
The assessment of the erosion prone area is based on several assumptions associated with the
recommended assessment methodology. These assumptions include:

• Storm events are of a sufficient duration to allow for development of a storm response beach
profile;
• The characteristics of the beach sediment are uniform both across and through the beach profile;
• the long-term erosion trend is independent of recession due to sea level rise.
• There are no physical features along the beach that would influence longshore sediment
transport; and,
• The beach has sufficient time to recover following a beach erosion event.

The above assumptions, combined with a 40% factor of safety lead to a conservative assessment of
erosion vulnerability. It is reasonable to apply a precautionary approach to erosion vulnerability
assessment given uncertainty regarding issues associated with sea level rise and storm events associated
with climate change impacts.


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