Improving Community Resilience in the Tenthill Catchment

Background

Improving Community Resilience in the Tenthill Catchment is a key initiative under the Resilient Rivers Initiative aimed at building community resilience in the Tenthill Catchment. The project is a response to the significant flood impacts experienced in 2011, 2013 and 2022, which caused severe economic, social, and environmental damage. These events led to extensive damage to the road network and agricultural land, and the loss of large amounts of sediment from creek banks and floodplain areas, necessitating substantial reconstruction efforts.

Implementation

The project engaged Alluvium to identify priority locations and to design suitable energy dissipation structures aimed at reducing the stream power and hence reducing damage to assets and erosion.

Site Selection

Located just downstream of Junction View, Blackfellow Creek is a partly confined gravel bed stream. This highly dynamic and energetic system is adapting to changes in flow regime, sediment transport capacity (due to crossings), and historic channel realignment (both anthropogenic and natural). The 2022 flood furthered the channel's widening and meander migration, and in response, the project reassessed flood damage and stream power, redesigning structures to be more resilient and robust. Three sites within a 12km stretch of Blackfellow Creek, from Junction View to Mount Sylvia, were identified as priority locations through extensive flood and LiDAR mapping.

Construction

Works include the installation of rock groynes, reprofiled banks, rock beaching, pile fields, channel realignment, and revegetation to ensure long-term stability and support vegetation growth. These structures, which will require 12,000 tonnes of imported rock and be stabilised with more than 10,000 native plants, are designed to redirect water flow, reduce erosion, and protect adjacent roads and properties.

Lockyer Valley Regional Council (LVRC) has contracted a local earthworks company with extensive knowledge of the area and its flood history to carry out the works. We are collaborating closely with landholders, especially those adjacent to the construction sites, to ensure minimal disruption and effective implementation. Additionally, we are working with TMR to manage road safety and access during the construction period.

Energy Dissipation Structures

The primary structures are rock groynes made from dense blue metal stone sourced from a local mine, which are dense and heavy enough to resist being easily moved by water. These groynes are constructed to be securely keyed in and difficult to displace. They will vary in size depending on the site's characteristics, the extent of erosion, and for desired stream redirection. Between the groynes, bank reprofiling and rock beaching will be done to extend the bank where it has eroded near the roads, providing stability.

Revegetation

To ensure long-term stability, we will establish a diverse riparian vegetation community at each site. This includes planting high-quality native vegetation such as sedges, ground covers, shrubs, and trees. These plants will be strategically placed between the groynes, on the banks, and across the floodplain, both upstream and downstream, to address various erosion mechanisms and enhance site stability.

Funding and Approvals

The project is funded through a collaboration with multiple levels of government, primarily by the LVRC of Mayors SEQ (COMSEQ) and Transport and Main Roads (TMR) for areas within the road reserve of Mount Sylvia Rd. It has received necessary approvals from the State Assessment and Referral Agency (SARA) and LVRC, including an Operational Works Permit. Cultural heritage and ecological surveys have been conducted to ensure compliance with relevant legislation.

In 2019, LVRC held a community workshop at Junction View Hall to discuss the project design and notify of upcoming works. However, due to flooding in 2021 and 2022, the project was postponed and re-designed. In October 2024, on-ground works officially began after a second community workshop was held to notify and discuss with landholders. LVRC is now working closely with local landholders and has engaged local contractors for construction works.

Project Sites

Stage 1 - Site 3

October - December 2024

Site 3 is located 900 metres downstream of the Mount Sylvia Road crossing in Junction View and focuses on a 100-metre section of the creek where, since 2011, approximately 100 metres of bank retreat has occurred and now sits only one to three metres away from Mount Sylvia Road. Designs are aimed to stabilise the left bank to protect the adjacent road and reduce land loss.

Stage 2 - Site 2

IN PROGRESS: Began December 2024. Expected completion February 2025.

Site 2 is located between Mount Sylvia Road crossing and Liftens Road in Mount Sylvia. The site is at significant risk of erosional channel change and meander development due to the steep bed grade and high stream power. During the 2022 flood there was significant bank retreat where it now sits only three to five metres from the road. The goal of the engineering works is to create a stable left bank to protect the adjacent road and reduce land loss.

Stage 3 - Site 1

Expected commencement: March-June 2025

Site 3 is located 600 metres downstream of Mount Sylvia Road crossing in Mount Sylvia. This area, affected by the 2013 flood, is prone to erosion and meander development due to its steep bed and high stream power. The 2022 flood caused significant meander development, increasing the stream length and leading to substantial bank retreat at three locations. Since the 2022 flood, landholders have undertaken in-channel works to straighten the channel. The goal of the engineering works is to create a stable right bank to protect the adjacent road and reduce land loss.