BMT WBM has undertaken a number of flood studies within the Maranoa Regional Council area for the towns of Mitchell and Amby.
Council endorsed the Amby Master Drainage Study report from BMT WBM at the General Meeting on the 23 September 2015. This study uses aspects of the Amby Flood Model Calibration Study (BMT WBM, July 2013) and Amby Flood Mitigation Study (BMT WBM, April 2014).
The intent of this assessment was to investigate the hydraulic behaviour of the existing Amby drainage system in order to identify any parts of the drainage network that did not meet the Queensland Urbane Drainage Manual (QUDM).
Several stormwater flooding mitigation measures were assessed for effectiveness in reducing stormwater flood risk in Amby. The issues the measures aimed to mitigate were selected through previous community consultation and inspection of modelled results. These options include: channelisation of the corner of Amby North Road and Creek Street, development of a representative pit and pipe network and an assessment of the new alignment of the Warrego highway.
The Amby Master Drainage Study has highlighted that the existing drainage network conforms to the QUDM design guidelines. It was found that all of the modelled cross drainage structures under the Warrego highway and through the railway embankment were performing to the guidelines. Where there are perceived stormwater inundation issues, such as the corner of Creek Street and Amby North Road, these are attributed to low hydraulic grade.
Council endorsed the Mitchell Master Drainage Study report from BMT WBM at the General Meeting on the 23 September 2015. This study uses aspects of the Amby Flood Model Calibration Study (BMT WBM, July 2013) and Amby Flood Mitigation Study (BMT WBM, April 2014).
This study forms part of the suite of investigations into Mitchell, focused on the management of the flood and stormwater risk in the Maranoa Regional Council Local Government Area (LGA). In particular, this assessment presents the methodology and findings of a Master Drainage Assessment of the Mitchell drainage system.
The report presents the current hydraulic capacity of the Mitchell drainage system. Infrastructure capacities have been assessed in accordance with Queensland Urban Drainage Manual (QUDM) hydraulic design standards. In addition, a flood mitigation measure addressing stormwater flooding trouble spots has been assessed.
The capacity of the existing drainage network was evaluated and compared to the design capacity recommendations in Queensland Urban Drainage Manual (QUDM). Results indicate that all of the cross drainage structures meet QUDM requirements. However, 14% of pit and pipe infrastructure was found to be non-conforming to QUDM guidelines.
The seven sections of the existing Mitchell network found to be non-compliant with QUDM guidelines were assessed for upgrade. Three of the seven sections are dominated by low hydraulic grade and are thus not suitable for infrastructure upgrade. A recommendation as to priority for upgrade of the four remaining sections has been made.