2019-07-09 P&E Agenda - Item 10 - Attachment 1 - Coastal Hazards Risk, Vulnerability and Adaptation Assessment

Noosa Shire Council Coastal Hazard Mapping                                                                                       34
Hazard Classification




5          Hazard Classification
5.1        Introduction
           To inform the Noosa CHAP risk assessment, it will be necessary to classify coastal hazard areas
           presented in this report. A short discussion on some key considerations is presented below.

5.2        Storm Tide inundation
           In terms of defining inundation hazards, floodplain and emergency management guidelines
           consider both velocity and depth of flows. The flood hazard classification as defined by Handbook 7
           - Australian Emergency Management Handbook Series is summarised in Table 5-1 and Figure 5-1.
           As part of risk and vulnerability assessments for the Noosa CHAP, the temporary inundation
           hazard associated with storm tide (and coincident catchment flooding and storm tide) may need to
           be further defined based on this or another similar classification.

5.3        Permanent Inundation from Sea-level Rise
           Tidal inundation is slowly emerging and characterised by very low flow velocities (less than 0.5
           m/s). Therefore, when defining the potential hazard associated with permanent inundation due to
           SLR, it is important to note the significance or consequence of the low velocity HAT plus SLR
           inundation hazard and its relationship to depth, frequency and duration of inundation.

           Multiple locations within the study area may experience frequent – possibly even daily – inundation
           by tidal waters under future climate scenarios. This inundation (even for areas subject to less
           frequent inundation) may result in a range of effects such as sediment deposition, salinization of
           soils, and/or reduced functionality of buried infrastructure services. These effects to both built and
           natural environments will gradually develop (over many decades) and are distinct in nature from
           more rapid onset hazards such as storm tide inundation. Therefore, the potential consequence and
           risk associated with permanent inundation from SLR will be assessed separately in subsequent
           CHAP phases3.

           Future climate performance analysis of affected infrastructure, services and natural environments
           adjacent to tidal waterways will need to be considered in conjunction with lower catchment and
           riverine flood and drainage assessments.

5.4        Coastal Erosion
           The open coast calculated erosion distances presented in this report may also require further
           consideration as part of ongoing work for the Noosa CHAP, in the event hazard reduction
           measures are undertaken in the future at a given location.




3
 It is noted that the Noosa CHAP storm tide and erosion prone area assessments and mapping described in this report include an
allowance for SLR.


G:\Admin\B22613.g.mpb.Noosa_CHAS\R.B22613.002.04.NSC_CHAP_Mapping.docx