UPDATED DA - Attachment 9A - Engineering Technical Memo

Explanatory Note – Flood Hazard Guidelines:

The relative vulnerability of the development, its built assets, employees and the public to flood hazard can be
assessed by using flood depth and velocity thresholds. The thresholds are related to the stability of both people and
vehicles in flood waters, and to buildings affected by flooding.

The Australian Disaster Resilience Handbook Collection – Flood Hazard Guideline 7-3 (AIDR 2017) provides the relevant
guidelines to assess flood hazard through three criteria as reflected in Figure 4.




Figure 4: Process for quantifying flood hazard (extract: Guideline 7-3 AIDR 2017)

Table 5: Combined hazard curves - vulnerability thresholds (extract: Guideline 7-3 AIDR 2017)

 Hazard                          Description
 Vulnerability
 Classification
 H1                              Generally safe for vehicles, people and buildings.
 H2                              Unsafe for small vehicles.
 H3                              Unsafe for vehicles, children and the elderly.
 H4                              Unsafe for vehicles and people.
 H5                              Unsafe for vehicles and people. All building types vulnerable to structural damage.
                                 Some less robust building types vulnerable to failure.
 H6                              Unsafe for vehicles and people. All building types considered vulnerable to failure.

Table 6: Combined hazard curves - vulnerability thresholds classification limits (extract: Guideline 7-3 AIDR 2017)

 Hazard                              Classification limit         Limiting still water depth           Limiting velocity
 Vulnerability                    (D and V in combination                     (D)                             (V)
 Classification                             m²/s)                              m                             m/s
 H1                                      D x V ≤ 0.3                          0.3                             2.0
 H2                                      D x V ≤ 0.6                          0.5                             2.0
 H3                                      D x V ≤ 0.6                          1.2                             2.0
 H4                                      D x V ≤ 1.0                          2.0                             2.0
 H5                                      D x V ≤ 4.0                          4.0                             4.0
 H6                                      D x V ≤ 4.0                           -                                -


244035 | M25-1015Tech | 19 February 2025                                                                                   Page 6