Marshalls Creek floodplain
Marshalls Creek is situated to the north of Brunswick Heads and has a long history of flooding, with a major flood event occurring recently in June 2005. Flood behaviour in this area is complex due to the multitude of creeks and hydraulic connections between major floodplains, including the Mooball Creek catchment in Tweed Shire and the Yelgun and Marshalls Creek catchments in Byron Shire. Both Councils therefore jointly completed a flood study in 2009 which covers the Cudgen, Cudgera, Mooball, Yelgun and Marshalls Creeks.
The Marshalls Creek catchment is the southern most catchment in this study and it covers an area of approximately 4200 hectares. Marshalls Creek flows into the Brunswick River approximately 1.2km from the mouth.
Marshalls catchment is linked to the Yelgun catchment at North Ocean Shores. There are culverts underneath Kallaroo Circuit linking the catchments. The catchment is bisected in a north-south direction by the Pacific Highway and the railway line.
Upstream of the Pacific Highway the catchment is predominantly agricultural and forested land. The area downstream of the Pacific Highway is significantly developed and this part of the catchment is a mixture of urban (including golf course) and forested areas. Townships within the Marshalls Creek catchment include Billinudgel, South Golden Beach, New Brighton and Ocean Shores.
Depending on the relative flood levels, flow between Mooball Creek and Marshalls Creek occurs in both directions and can change during a single flood event. Lacks Creek and Marshalls Creek converge upstream of Billinudgel. The floodplain significantly increases in size at the confluence of the creeks. The flow is then constrained by the railway line before passing through the Pacific Highway bridges. Downstream of the Pacific Highway the floodplain is also large, with water backing up into the Golf Course area.
Other significant flood events occurred in May 1987 (this event is often referred to as “the Mothers Day Flood”) and March 1974. A smaller event also occurred in January 2008.
Documents
The original Marshalls Creek Flood Study was finalised in November 1986.
Following this the Marshalls Creek Floodplain Management Plan was adopted by Council in November 1997.
Since the above documents were completed, Council has completed the Tweed – Byron Coastal Creeks Flood Study. This study helped both Council’s better understand how the floodplain between the shires interacts across the shire boundary. This study includes the Marshalls Creek Catchments and was adopted by Council on11 February 2010. Council also adopted at the same meeting a specific climate change assessment using Byron Shires parameters. The 100 year flood event which Council uses to calculate its Flood Planning Levels for this catchment can be found at Annexure 3-6 of this document.
Council is currently combining the Marshalls, Simpsons and Brunswick Catchments with the North Byron Flood Study. The study will consider the urban areas of Mullumbimby, Brunswick Heads, Ocean Shores, New Brighton and South Golden Beach.
Minutes from the Flood Risk Management Committee meetings for this project can be found at Floodplain Risk Management (Marshalls Creek) Project Reference Group.
A review of the Marshalls Creek Floodplain Management Plan is now required, however, this project has been delayed until the new Brunswick River Flood Study has been completed.