The Lockyer catchment provides significant environmental, economic and social values for the region. It supports a diverse range of agriculture including fruit, vegetables, horticulture and grains, with the region supplying 35% of Queensland’s vegetable supply. It also contains areas of World Heritage listed Gondwana Rainforest and has a high biodiversity value. The catchment is well known for its rich alluvial soils and ideal growing climate which enable the production of high quality crops.
The topography of the Lockyer catchment is varied and is characterised by steep slopes, gullies and confined channels which can have high water flow rates during storm events. This combination of natural features and human impacts on the landscape can influence how water moves through the catchment.
Erosion in these steep slopes results in sediment being deposited downstream, mainly in creeks and rivers. The sediment carries nutrients into streams and rivers, and can impact the quality of drinking water in Brisbane and Moreton Bay Marine Park.
Vegetation in the catchment slows and absorbs water, reducing the amount of sediment being carried downstream. It also allows water to seep into the ground where it recharges groundwater aquifers. The Concreter Lockyer Valley catchment’s natural features include basalt, enabling good levels of water infiltration and groundwater recharge. The basalt is capped by sandstone formations which can produce naturally saline groundwater. The catchment also has areas of deep alluvial plains which are made up of permeable silts, sands and gravels that can absorb and hold water for longer, recharging groundwater aquifers.
Many of the creeks in the Lockyer catchment flow through urban, rural and agricultural areas. The construction of levees and weirs restricts the flow of water, increases erosion, and removes vegetation along creek banks. This can result in higher flood induced forces on bridge structures and increase the risk of failure during severe flood events.
The construction of wetlands in the Lockyer catchment helps to reduce flood induced erosion by holding and trapping sediments and allowing for groundwater recharge. However, the loss of native vegetation in the upper reaches of the catchment has reduced their ability to absorb water and maintain soil stability.