Normanby catchment story – Physical features

Select from the tabs below

• Introduction
• Catchment Overview
• Physical features
• Natural values
• Traditional Owners
• Economic values
• Threats
• Conclusion
• Acknowledgments

The Normanby Catchment features a complex range of geology and topography, the hills and dips in the landscape, which contribute to the diversity of plants and animals that live within the catchment. Starting from the bedrock and the soils that help to shape the land, there are strong connections that exist with how water flows across the landscape and into creeks and groundwater.

Main image. Rocky outcrop on Mount Amy - provided by Robbie Burns © Queensland Government.

Geology and topography - upper elevations

Many different rock types combine to make up the geology of the Normanby Catchment.

The upper elevations of the catchment are underlain by mostly sedimentary (sandstone) and metamorphosed sedimentary rock (arenites, mudrocks, rudites), together with granite, basalt and other minor rock types. The catchment includes two relatively large fault lines.

Main image. Rocky outcrop on Mount Amy - provided by Robbie Burns © Queensland Government.

Melsonby sandstone of the upper catchment - provided by Matt Wallace © Queensland Government.

Water runs quickly off the areas of high elevation meta-sedimentary rock and granite while in contrast, water seeps down through the high elevation sandstone and recharges the groundwater. This groundwater storage provides artesian water to properties lower in the catchment and feeds many springs at the base of the sandstone escarpments. The larger springs in turn supply base flow to several streams including Bridge Creek and the Jack River in the east, and Jungle Creek and the Hann River in the west.

The metamorphic and volcanic rocks (excluding basalt) are harder and less permeable and have steeper topography allowing more runoff and less groundwater recharge.

An area of basalt in the Lakeland region contains locally significant groundwater supplies which feed numerous springs, and also provides irrigation water and fertile soils for farming.

Main image. The East Normanby valley - provided by Andrew Brooks. Linked images. Higher elevation Dalrymple Sandstones that extend west from the Endeavour catchment under the Battle Camp Range to Laura, and north to Bathurst Heads - provided by Graham Herbert ©Queensland Government. Spring on Basalt Hill - provided by Robbie Burns © Queensland Government.

Linked video. Kings Plains showing meta-sedimentary ridges in the background - provided by Tim Hughes.

Geology and topography - lower elevations

Large areas of colluvium have deposited on the slopes following erosion of the higher elevation geologies or rock types.

The rest of the catchment is very flat floodplain and estuary (alluvium and other unconsolidated sediments). Because of the low gradient, water movement is very slow, and during flood events much of the floodplain is inundated by sheet water flow between poorly defined watercourses.

Alluvium and colluvium often consist of very dispersive sediments and can be very prone to erosion.

There are extensive wetlands across the catchment, including large freshwater systems of swamps and billabongs known as palustrine wetlands, together with riverine wetlands along waterways and lacustrine wetlands or lakes. Most of the wetlands sit in the alluvium and colluvium which is underlain by hard geologies (mudrock).

Main image. Lower reaches of the Normanby River - provided by Andrew Brooks.

Rainfall

Cape York usually experiences annual wet and dry seasons, with most of the annual rainfall typically falling between November and March. The average annual rainfall across the catchment ranges from approximately 750 to 3,300 millimetres a year, with higher rainfall occurring along the eastern ridge in the catchment.

This region also experiences extreme weather events such as cyclones and monsoonal troughs during the wet season. These high volume rainfall events typically bring annual flooding and road closures. They can also significantly affect vegetation with riparian, or riverside, vegetation along the Deighton River flattened by Tropical Cyclone Ita during April 2014.

Water quality

There are many factors that can influence water quality, including erosion, sedimentation, nutrients, pesticides and salinity.

Erosion causing suspended solids in water (turbidity), and sedimentation have major impacts on water quality. Activities that have contributed to the increased erosion include linear infrastructure such as roads and fences, over-grazing and soil and bank degradation, changes in fire regimes and crop tillage. Subsequent sedimentation can bring about the loss of downstream aquatic habitat due to the in-filling of channels and lagoons.* Erosion and sedimentation is discussed further on a following slide.

Turbid waters of the catchment - provided by Andrew Brooks.

Nutrient concentrations are generally low under base flow conditions. Increased ammonia and chlorophyll-a concentrations have however been recorded during the dry season at locations on the East Normanby River, the Normanby River (Battlecamp Rd) and 12 Mile Waterhole in Rinyirru (Lakefield) National Park (Cape York Peninsula Aboriginal Land, CYPAL), which may be related to cattle congregating at waterholes.*

High nutrient concentrations** have also been recorded in the Laura River downstream of the Lakeland farming. These very high concentrations indicate that surface water run-off or groundwater leaching of fertilisers from farms is impacting on water quality, however, these basaltic soils have naturally higher nutrient concentrations than downstream sodic soils and erosion of these soils together with runoff and groundwater leaching may also contribute. Nutrients can increase algal growth, which depletes oxygen and degrades aquatic habitat and stock water quality.*

Nutrient concentrations can also be higher in the estuary than other parts of the catchment during the dry season, which indicates that tidal flushing from coastal saltpans and associated bank erosion may be a significant year round source of nutrients and sediments to the estuary and Princess Charlotte Bay.*

Very low herbicide concentrations have been detected in the Laura River downstream from Lakeland, however all herbicides were well below the national guideline levels and unlikely to significantly impact aquatic ecosystems.*

Some areas in the catchment also experience elevated salinity in the dry season, following evapotranspiration.

Water quality in wetlands of the catchment can be affected by feral pigs, cattle and horses disturbing the soil and increasing levels of nutrients, bacteria and turbidity (water clarity). Jack Lakes are shallow wetlands that can be particularly turbid due to disturbance by feral pigs and cattle in the shallow top lake.*

Disturbing sediments in coastal areas can also impact water quality if there are acid sulfate soils.*** When these soils come into contact with oxygen, the pyrite in the soil reacts with the oxygen to produce sulfuric acid, which can directly impact water quality but also attack soil minerals, releasing metals into the waterways.

The Normanby Catchment Water Quality Management Plan (2014) identifies water quality impacts and prioritises actions required to maintain or improve water quality in the Normanby catchment and receiving waters.*

The Eastern Cape York Water Quality Improvement Plan (WQIP) (2016) identifies water quality issues and actions to maintain and improve the rivers, wetlands and reefs of eastern Cape York including the Normanby Catchment. The WQIP has been designed to support the Reef 2050 Long-Term Sustainability Plan, which sets targets to reduce sediment and nutrient pollution to the GBR. It supersedes the Normanby Catchment Water Quality Management Plan.****

The Great Barrier Reef Catchment Loads Modelling Program estimates average annual loads of key pollutants (sediment, nutrients and pesticides) for each of the 35 catchments draining to the Great Barrier Reef (GBR) as part of the Paddock to Reef program. It assesses progress towards the Reef Plan water quality targets.^ A technical report has been prepared for the Cape York region.^^

Main image. Sedimentation along the West Normanby River - provided by Robbie Burns ©Queensland Government.

Linked image. Acid sulfate soil - provided by ©Queensland Government.***

*Normanby Catchment Water Quality Management Plan (Howley et al 2014) and references contained within - see links at the end of this map journal for further information.

**Normanby River Water Quality (Howley & Griffith University undated) – see links at the end of this map journal for further information.

***Acid Sulfate Soils Explained (Queensland Government 2017) - see links at the end of this map journal for further information.

****Eastern Cape York Water Quality Improvement Plan – Draft for Community Consultation (Cape York Natural Resource Management 2016) – see links at the end of this map journal for further information.

^Great Barrier Reef Report Card 2012 and 2103 Reef Water Quality Protection Plan – Catchment Pollutant Loads Results (Department of Environment and Science, undated) – see links at the end of this map journal for further information.

^^Modelling Reductions of Pollutant Loads due to Improved Management Practices in the Great Barrier Reef Catchments, Cape York NRM Region, Technical Report, Volume 2 (McCloskey et al 2014) – see links at the end of this map journal for further information.

Water flow

Water flows across the landscape into streams and channels and eventually into Princess Charlotte Bay and the GBR. Water that doesn’t head to the Bay either sinks into the ground, where it supports a variety of terrestrial and groundwater dependent ecosystems, contributes to overland flow, or is used for other purposes, like agriculture.

Fast water flow following rain - provided by Andrew Brooks.

*Please note this application takes time to load.

Erosion and sedimentation

Soils of the catchment are associated with high levels of natural erosion and accelerated rates of erosion have been observed in association with the clearing of land for roads and other developments.* Accelerated erosion has been recorded in parts of the catchment, including the upper Laura River, the West Normanby and East Normanby rivers and the mid reaches of the Normanby River.**

Both surface (hillslope) and subsurface erosion (gully, bank, rill and scald erosion) occurs across the catchment, however, the subsurface channel bank and gully erosion is most dominant. Gully erosion that has been accelerated by land use occurs along the East, West and Granite Normanby rivers, and the Laura River between Laura and Lakeland. Bank erosion occurs throughout the entire catchment, but the extent to which this process is accelerated by land use is not as clear cut as for gullies.

Erosion that has been accelerated by land use (track) - provided by Robbie Burns © Queensland Government.

Complex ‘macrochannels’*** are found in parts of the catchment, primarily the upstream reaches, and are a function of long term channel evolution over ancient glacial cycles (e.g. 10,000 to 30,000 years ago). Many macrochannels of the catchment have smaller inset floodplains and/or benches deposited within these larger channels, and these floodplains or benches represent large stores of sediment.

Not all of the sediment eroded from the catchment makes it to the sea; some is deposited on these benches, and also on mid-channel islands and floodplains where water flows over the high 'macrochannel banks' of the main channel (typically in the downstream half of the catchment).

Most the of the ‘bank erosion’ within the catchment also occurs on these inset benches, and smaller channels, rather than the ‘macrochannel banks’ of the main channels.

Main image. Gully erosion - provided by Andrew Brooks.

Linked images. Vegetated inset bench in the 'macrochannel' of the upper catchment - provided by Robbie Burns © Queensland Government. Vegetated mid-channel island, location to be confirmed - provided by Andrew Brooks.

*Biggs and Philip (1995) in Normanby Catchment Water Quality Management Plan (Howley et al 2014) – see links at the end of this map journal for further information.

**Normanby River Water Quality (Howley & Griffith University undated) – see links at the end of this map journal for further information.

***Age, Distribution, and Significance within a Sediment Budget, of In-channel Depositional Surfaces in the Normanby River, Queensland, Australia (Pietsch et al 2015) – see links at the end of this map journal for further information. Enlarged inset map provided below.

Special feature – alluvial gullies

In some areas, alluvium can be up to 20 metres deep or more and can form 'terraces'. Deep gullies that are cutting into this alluvial material can contribute large volumes of fine sediment from very confined areas.

Much of the active gully erosion that currently occurs within the catchment is into these large alluvial terraces that were deposited during the last inter-glacial period 20,000 to 30,000 years ago. This alluvial material has weathered over this long period of time to form highly sodic (i.e. high in sodium) and dispersible (i.e. unstable and breakdown quickly) silts and clays which are highly prone to erosion when disturbed.

Gully erosion - provided by Robbie Burns ©Queensland Government.

Some of these terraces also exhibit old stable gullies that are of variable age, which are likely to be a response to fluctuations in the sediment supply and hydrology over the Holocene (last 10,000 years). However, the difference between these past phases of gullying (and probably bank erosion) and the present phase is that the current active gullies have been synchronously reactivated since cattle and Europeans were introduced to this landscape. There is also evidence that the current gullies are cutting into greater depths than past phases, and into material that hasn’t been eroded for 30,000 years.

Gully erosion - provided by Robbie Burns ©Queensland Government.

Main image. Alluvial gully erosion - provided by Andrew Brooks.

Water quality and sediment tracing

Flood event water quality monitoring down the catchment showed that suspended sediment concentrations are very high on the West Normanby, East Normanby and Laura rivers, however concentrations were substantially lower further downstream and lower again near the mouth due to dilution and increased deposition downstream. Nutrient levels followed a similar trend.*

Sediment tracing studies indicate that erosion occurring on the coastal plain is a major source of fine sediment to Princess Charlotte Bay bed sediments. A natural channel avulsion occurring in the Bizant River appears to be a major contributor, but tidally driven bank erosion and coastal plain stripping are other major sources. However the processes driving this erosion are not yet well understood.** More recent tracing shows that during flood events the major source of sediment to Princess Charlotte Bay comes from the upper catchment and that the coastal plains are a smaller source.***

The Great Barrier Reef Catchment Loads Modelling Program**** provides a report on contaminants across GBR catchments, including sediment in the Cape York region, and the Eastern Cape York WQIP identify water quality issues and actions to maintain and improve the rivers, wetlands and reefs of eastern Cape York.^

At a Commonwealth level, the National Environmental Science Programme reports on reducing erosion and sedimentation in the Normanby Catchment and GBR.^^

*Normanby River Water Quality (Howley and Griffiths undated) - see links at the end of this map journal for further information.

**Coastal Erosion and Geochemistry, What's Eating the Coast (Olley undated) - see links at the end of this map journal for further information.

***Howley and Olley (in prep) - to be provided.

****Modelling Reductions of Pollutant Loads due to Improved Management Practices in the Great Barrier Reef Catchments, Cape York NRM Region, Technical Report, Volume 2 (McCloskey 2014) – see links at the end of this map journal for further information.

^Eastern Cape York Water Quality Improvement Plan – Draft for Community Consultation (Cape York Natural Resource Management 2016) – see links at the end of this map journal for further information.

^^Reducing Sediment Sources to the Reef: Managing Alluvial Gully Erosion (Brooks et al 2016) – see links at the end of the ma journal for further information.

Special Feature - riparian rainforest

Riparian rainforest commonly refers to rainforest that is growing in association with a waterway or wetland, and can also be referred to as gallery rainforest.

There are remnant rainforests and scrubs growing along the Normanby and East Normanby rivers and several small tributaries. Often these rainforest pockets are growing on benches or inset floodplains in the 'macrochannel' (main channel), and are inundated by floodwaters much more frequently than the majority of the alluvial landscape or floodplain outside of the macrochannel.

Sediment is deposited on these benches, and over time the rainforest expands through a positive feedback between the vegetation, sedimentation, flood inundation and fire suppression. This riparian rainforest provides reinforcement of, and therefore stabilises, the bank channel through the extensive tree root networks and buttresses. There is substantial storage capacity for sediments in these vegetated banks and they are aggrading.

Main image. Riparian rainforest of the Normanby River - provided by Tim Hughes.

Linked images. Tree roots and buttresses providing stabilisation to banks - provided by Andrew Brooks.at the end of this map journal for further information.

---

Last updated: 13 October 2017