Pumicestone Catchment Story

Transcript

The Pumicestone catchment is located north of Brisbane, between Caloundra and Caboolture.

It contains significant features such as Pumicestone Passage, which is part of the Moreton Bay Marine Park and internationally important Ramsar site, Bribie Island, the D’Aguilar Range and Glasshouse Mountains.

The sub-catchments that make up most of the area include the Six Mile, Ningi, Beerburrum, Lower Elimbah, Bullock, Glass Mountain, Tibrogargan, Coonowrin, Mellum/Coochin, Halls, Bells, Lamerough, and a number of smaller coastal creek systems, as well as Bribie sub-catchments.

The Pumicestone catchment provides a wide range of land and water-based recreational activities that support local lifestyles.

National parks and forestry reserves around the Glass House Mountains and Bribie Island are well known for their protected bushland areas and are important for tourism.

To effectively manage this beautiful area it’s important to understand how water flows in the catchment and how it can be affected by land use and management practices.

Prior to development, tall open forests of scribbly gum and Blackbutt dominated most of the mainland catchment areas, and wetland forests of paperbarks, mangroves and heath grew on coastal plains.

This vegetation slowed water coming off the land, retaining it longer in the landscape.

Today, more than half the catchment has been cleared to provide important rural industries such as forestry plantations, pineapples, strawberries, turf farms and animal husbandry.

The area is also home to a population of more than 60,000 people.

Residential and industrial developments can also modify water flow.

These developments can change the shape of the landscape and add impermeable surfaces, such as roads, which lead to increases in run-off.

While roads, railways and creek crossings are essential, they modify the flow of water and may act as barriers, redirecting water through single points or culverts.

Off-stream dams and other similar infrastructure can also change the natural water flow patterns.

When it rains much of the water flows across the surface of the land into local streams and eventually into Pumicestone Passage.

The remaining water either sinks into the ground where it supports a variety of terrestrial and aquatic groundwater-dependent ecosystems or is used for other purposes.

The Glasshouse Mountains and D’Aguilar Range have relatively steep slopes, which create the potential for increased run-off that may lead to flooding in areas where the floodplain has restricted channels and gullies.

Groundwater comes to the surface in areas where permeable weathered basalt rock meets a less permeable underlying geology.

Groundwater may also discharge from fractured rock aquifers, typically along foot slopes and drainage lines in the steep slopes, this can cause land slips.

Moving from these steeper slopes, the restricted channels and gullies eventually flatten out to form waterways that meander across the coastal lowlands.

With the exception of Beerburrum, where the floodplain is constricted due to the underlying rock formation downstream.

These creeks and rivers pass through alluvial areas which have formed over thousands of years and are made up of silt, sand, gravel and other materials deposited by rivers.

They store and release water like a sponge.

Groundwater generally seeps from alluvia into nearby streams prolonging the time they are in flow.

For example Paperbark swamps act as major recharge areas in coastal and sub-coastal floodplains with trapped water soaking down into the groundwater.

Water is released from the sub-catchments into the Pumicestone Passage in a variety of ways depending on the catchment and the rate of flow.

Each creek system is complex and dynamic and reacts differently depending on a variety of influences such as the level of the groundwater aquifer, the tides and even the wind direction.

For example, during high flows in the lower southern catchment, water overtops the channels and spreads over the floodplain joining Elimbah, Bullock and Ningi Creeks.

Glass Mountain Creek has many different-sized channels which eventually merge.

At other times, the lower catchment waterways are slow and meandering, within channels or forming many wetlands.

These channels eventually become estuarine because the freshwater mixes with marine water before flowing into the Pumicestone Passage.

The Pumicestone Passage is one of the few barrier estuaries in Australia.

It has extensive mangrove forests, seagrass meadows, inter-tidal sandbars and mud flats, which provide valuable habitat for fish, dugong, turtles, crabs, oysters, juvenile prawns and a wide variety of local and migratory waders and shorebirds.

At the lower end of Tibrogargan Creek, also known as Hussey Creek there is almost no water movement from tidal action. This is because two different tides meet.

Tripcony Bight, a wide estuary area beside the lower reaches of Tibrogargan Creek, has formed due to this very low energy area.

Every drop of rain that falls in the Pumicestone catchment has its own story, its own journey from landfall to the Passage and finally the ocean.

Drops fall, join and flow together down the catchment or through the ground.

Together, they shape and nurture the landscape and intertwine with the stories of the plants and animals, including humans, that share the catchment.

Last updated: 2 June 2016