The objective of this study was to assess flood affection to properties located inside Coonamble Levee due to two levee breach scenarios, with two design floods investigated for each scenario. The levee failure scenarios defined by DECCW after consultation with the State Emergency Service (SES) included the following:

• A 75m gap in the Levee 0.5m above the natural surface near Coonamble Hospital; and
• A 75m gap in the Levee 0.5m above the natural surface in the vicinity of northern end of Namoi Street.

This report is structured as follows:

• Section 1 – Introduction
• Section 2 – Available Data: Provides details on the data used in this study
• Section 3 – Hydraulic Modelling: Estimation of flood levels inside Coonamble Levee for the levee breach scenarios
• Section 4 – Flood Affection to Properties: Assessment of flood affection to buildings inside Coonamble Levee for the levee breach scenarios
• Section 5 – Conclusions: Key conclusions on flood affection inside Coonamble Levee for the levee breach scenarios assessed in this study.