The major landforms of the catchment are the steep mountain ranges that form the catchment boundaries, the steep, low hills that form the boundaries of the sub-catchments, the low lying floodplain that forms on the coastal plain towards the ocean, and the tidal estuary near the mouth.

The land uses of the Maroochy catchment are diverse. The original basically agrarian land use pattern has been overlain by a rapid increase in population and hence land utilized for residential area.

Located on the Sunshine Coast in South East Queensland, the Maroochy River drains an area of approximately 640 square kilometres of subtropical coastal plain. Bounded by the Blackall Ranges in the north and west, and the Mooloolah Range in the south, it flows into the South Pacific Ocean near the town of Maroochydore.

The catchment area extends 22km inland from the coast, with a north south distance of 35 km at the longest axis. The majority of the catchment is contained within the old Maroochy Shire area, with small parts in old Noosa Shire and the City of Caloundra.

The Maroochy River divides into two arms at its tidal limit, with these being called the North and South Maroochy Rivers. Below the confluence of these lies the estuary, termed the Maroochy River. Five other subcatchments make up the drainage of the Maroochy river, these being:

• Eudlo Creek
• Paynter Creek
• Petrie Creek
• Coolum and Yandina Creeks
• Stumers Creek

Remnant native vegetation covers approximately one quarter of the subcatchment area, the majority of this is on freehold land not in reserves. As this entire subcatchment is tidal, the riparian vegetation is dominated by mangrove communities of Grey Mangrove (Avicennia marina) and Orange Mangrove (Bruguiera gymnorrhiza) and saline herbland of rushes (Juncus sp.) and salt grasses (Sporobolus sp.).

The coastal areas away from the riparian zone are populated by frontal dune scrub. The main species are Brown Salwood (Acacia aulacocarpa) and Coast Banksia (Banksia integrifolia); this is interspersed with areas of open and closed Wallum heath populated by Wallum Banksia (Banksia aemula), Swamp Banksia (Banksia robur) and Grass Tree (Xanthorrhoea australis). This gives way to Eucalyptus – Melaleuca – Lophostemon grassy woodland, which occurs on the floodplain areas away from the river channel. The low lying areas and drainage lines subject to short-lived periodic inundation support pure stands of Broad Leaved Tea Tree (Melaleauca quinquenervia). The areas of higher elevation support open woodlands of Forest Red Gum (Eucalyptus tereticornis), Broad Leaved Tea Tree, and Swamp Box (Lophostemon suaveolens).

The upper slopes and crests of the low hills bounding the subcatchment support open forests of Blackbutt (Eucalyptus pilularis) interspersed with pockets of gallery forest and Piccabeen Palms (Archontophoenix cunninghamiana).

Comprising the tidal section of the Maroochy River, the Maroochy Estuary begins at the confluence of the North and South arms of the Maroochy River, and drains into the South Pacific Ocean at Maroochydore.

For its entire length, the Maroochy Estuary is tidal, and drains at a low angle through Quaternary alluvium of gravel, sand, silt and clay forming a level to slightly undulating but narrow floodplain that is initially constricted by steep, low hills. This opens out and becomes quite extensive once the river leaves the low hills. The channel begins to widen at this point, with several channel islands occurring.

Near the mouth, the landform changes into coastal sand dunes of Holocene wind blown sand, Pleistocene tidal sand, and saline muds which are deposited around the shoreline of the river.

The lower reaches of the estuary are a highly complex and dynamic system of channels, sand banks, intertidal shoals and sand bars. Two islands, Goat and Channel, divide the estuary into two channels, north and south. The river mouth is migratory, moving north and south according to the prevailing coastal conditions, and cyclonic and flood events

The slopes and summit of the Blackall range, which forms the western boundary of the subcatchment, supports extensive areas of Blackbutt (Eucalyptus pilularis) and Grey Gum (Eucalyptus punctata) open forest. Other species found in this area are Turpentine (Syncarpia glomulifera), Forest She Oak (Allocasuarina torulosa) and Tallow Wood (Eucalyptus microcorys). This vegetation also occurs on the low steep hills of the lower subcatchment, which are an extension of the Blackall Range.

The alluvial floodplain that forms the bottom end of the river is almost entirely cleared for agriculture, but still has some isolated individual Forest Red gums (Eucalyptus tereticornis).

The South Maroochy river rises on the northern slopes of Towen Mountain, a small range complex that is a spur of the Blackall Ranges, which form the western boundary of the subcatchment. It confluences with the North Maroochy River near the town of Yandina to form the estuary. Within the South Maroochy subcatchment are two of the major dams within the region, Cooloolabin and Wappa.

The landform of the headwaters is a small hill complex of Laterised Tertiary basalt, grading to low, undulating hills founded on the same landform that make up the upper half of the subcatchment. Throughout the upper subcatchment, the landform never develops a continuous alluvial plain of any size as this is precluded by the steepness of the terrain through which the river flows. However, there are small creek lines and some valley flats near the end of the upper half, at the boundary of this particular landform.

The lower half of the subcatchment consists of low steep hills formed on Rhyolite and Andesite. The land form in this area is similar to that found in the upper subcatchment, low, steep hills that prevent the development of alluvial plains with only small valley flats being observed.

Once the river exits these low hills, it is able to form a short alluvial plain just prior to its confluence with the North Maroochy River. This alluvial plain consists of undifferentiated freshwater sediment.

The upper subcatchment supports remnant patches of rainforest species, but the majority of this area has been cleared for grazing. The areas remaining under vegetation are usually those that are too steep for clearing, or on the tops of steep hills. The lower areas of the upper subcatchment still support remnant stands of Flooded Gum (Eucalyptus grandis) in riparian areas.

The low hills of the Yandina Creek headwaters are populated by open forests of Blackbutt (Eucalyptus pilularis) and Grey Gum (Eucalyptus propinqua) on the crests and upper to mid slopes. The same landform in the upper Doonan Creek catchment is populated by Scribbly Gum (Eucalyptus racemosa) and Bloodwood (Corymbia sp.), which gives way to Banksia and Tea-tree shrub land on the lower slopes.

The riparian areas of both creeks are populated by remnants of Forest Red Gum (Eucalyptus tereticornis) open forests and fringing areas of rain forest species.  This landform is also populated by large areas and numerous fragments of Tea-tree (Melaleuca quinquenervia) wetlands and Wallum Heath. The largest areas of vegetation occur in the Doonan Creek catchment, which flows into an area of extensive wetlands located on the upper floodplain, and in the riparian areas of Coolum Creek.
Toward the confluence with the Maroochy estuary, small areas of Grey Mangroves (Avicennia marina), and rainforest appear along the margins of the river.

Incorporating Coolum, Yandina and Doonan Creeks, this large subcatchment drains the northeastern quarter of the Maroochy River Catchment. These creeks rise in the Eumundi Range, which is the eastern end of the Blackall Range after it turns toward the coast to form the northern boundary of the Maroochy Catchment. The western boundary is formed by the Ninderry Range, and offshoot of the Blackall Range. A small, unnamed line of hills running north south from the Eumundi Range separates Yandina and Doonan Creeks. Once clear of this obstacle, they confluence to form Coolum Creek, which flows into the Maroochy River Estuary.

The headwaters of Yandina Creek rise in low undulating hills composed of soil derived from Rhyolite and Andesite, a formation that also forms Ninderry Range, and the line of low hills that separate Yandina and Doonan Creeks. Doonan creek arises in undulating rises formed of sandstone.

In their upper catchments, both creeks form a narrow alluvial area immediately adjacent to the creek lines consisting of undifferentiated freshwater sediments mixed with colluvial material from the surrounding hills. These are discontinuous initially, but quickly coalesce in continuous floodplain formations.

Both creeks form a wide flood plain after exiting the confines of the low hills in which they arise, at about the tidal limit, upstream of the confluence that forms Coolum creek.

This floodplain is formed on Holocene and Pleistocene sand deposits, and is nearly level, and entirely below the 5m ASL contour. It is on this floodplain that the confluence of Yandina and Doonan Creeks forms Coolum creek, which drains into the Maroochy estuary.

The summit and upper slopes of Mt Coolum, the upper catchment of the south arm, support small fragments of banksia heath lands, populated by dwarf White Banksia (Banksia integrifolia), with a shrub layer of Dogwood (Jacksonia scoparia) and Leptospermum species. This gives way to remnant fragments of Forest Red Gum (Eucalyptus tereticornis) open forest on the lower slopes and foothills. This grades to open forests of Scribbly Gum (Eucalyptus racemosa), which occur on the crests and upper slopes of the low sandstone hills. The lower slopes are populated by Broad-leaved Tea-tree (Melaleuca quinquenervia) woodland, which grades to closed forest on the wetter, low lying areas around drainage lines and in coastal swamps.

The north arm flows through Wallum Heath, which consists of areas of open heath populated by Wallum Tea Tree (Melaleuca nodosa) Swamp Banksia (Banksia robur) and Grasstree species (Xanthorrhoea sp.) in the low lying, wetter areas, intergrading with sedgeland.
|Although vegetation covers more than half of the Stumer Creek catchment (52%), urban areas (41%) are rapidly gaining as many new housing estates are under construction or planned. All other land uses account for the remaining 7% of the land area. The vegetated areas of the catchment are concentrated in the northern half, with the southern half being almost entirely urban.

Although not part of the Maroochy River Catchment, Stumer Creek is closely associated to it as it drains a coastal area between the Maroochy Catchment and the ocean.

Stumer Creek is a two-branched coastal creek draining the area around the town of Coolum and the wetlands in the southern end of the Noosa National Park. The north and south arms diverge very close to the mouth. The upper catchment of the south branch begins on Mt Coolum, a Tertiary Trachyte plug that dominates the surrounding area. To the north of Mt Coolum are low sandstone hills that also drain into the south arm of the creek. The lower reaches of the south arm, and the entire north arm drain areas Holocene windblown sand plains.

The mouth of Stumer Creek is often plugged by ocean sand during periods of low rainfall, forming a lagoon. This situation is only altered when sufficient rain falls in the catchment to develop a flow strong enough to erode the sand plug. The mouth of Stumer Creek is constrained in a relatively stable position by outcrops of organic sand rock under the beach.

The steepness of the upper catchment of the south arm means that the stream is ephemeral, only flowing during periods of prolonged heavy rain. The creek rises very quickly due to the impervious nature of the urbanized upper catchment. The creek channel is deeply incised in the upper reaches, but is heavily modified in the middle and lower reaches by flood mitigation works.

The north arm rises in the foothills of Mt Peregian, and associated low hills. The stream originates in the Wallum wetlands of the Noosa national park, with the channel not coalescing until two-thirds down its length, close to the confluence with the south arm. In contrast, the north arm has not been modified by flood mitigation works.

The major towns within the subcatchment are Nambour (pop 11 832) and Bli Bli. Nambour is the administrative centre of the old Maroochy Shire. The major land uses within the subcatchment are living space, grazing and cropping. Living space, both urban and rural residential, utilize less than 1000 ha of the subcatchment. The urban areas are concentrated mainly in Nambour and  Bli Bli with the rural residential areas satellite from these.

Grazing, both beef and dairy, is concentrated largely in the upper reaches of the subcatchment, where the soils are better and less prone to the effects of flood. This land use occupies slightly over 1000 Ha.

Part of the Maroochy River catchment, Petrie Creek rises in the steep slopes of the Blackall Ranges near the town of Hunchy, and confluences with the Maroochy River in it’s estuary upstream of Maroochydore.

In the headwaters, the geology and landform is affected by the Tertiary Laterised Basalt of the Blackall Range, and the higher gradient of the creek bed. The drainage line is incised, with the slopes of the bounding hills being steeper. There are small, discontinuous valley flats  along the channel boundaries.

Downstream of Nambour, the creek drains at a low angle through Quaternary Alluvium of gravel, sand, silt and clay forming a level to slightly undulating floodplain bounded by steep low hills replacing the discontinuous valley flat system.

Remnant vegetation covers nearly one third of the subcatchment. This is contained in State Forests, National Parks and remnant vegetation on private land. The types of remnant vegetation are closely linked to landform. The upper slopes and crests of the steep low hills largely support open forests of Blackbutt (Eucalyptus pilularis) and Grey Ironbark (Eucalyptus siderophloia), grading to Tallowwood (Eucalyptus microcorys) and Brush Box (Lophostemon confertus) forest, interspersed with pockets of gallery forest and palms sheltering in protected areas. This vegetation type becomes mixed with Red Bloodwood (Eucalyptus intermedia) in the upper subcatchment. The riparian zones in the upper catchment support areas of subtropical rainforest, whilst in the lower subcatchment the alluvial plain supports remnants of Melaleuca and Casuarina open forest. Near the confluence with the Maroochy River, there are several patches of remnant Grey Mangroves (Avicennia marina) inhabiting the creek margins.

Cropping, including annual crops, semi permanent crops and sugar cane occupy about 1600 Ha in the subcatchment. Annual and semi-permanent crops are mostly concentrated on the slopes and valley flats of the upper catchment, in less flood prone areas. Sugar cane is grown exclusively on the wider alluvial plain of the lower catchment, near the confluence with the Maroochy estuary.

The upper catchment is almost devoid of vegetation due to clearing for grazing and residential areas, but originally supported closed forests of Blackbutt (Eucalyptus pilularis) and Blood wood (Eucalyptus sp.).

The northern side of the creek supports remnant areas of Tallowwood (Eucalyptus microcorys) and Bloodwood (Eucalyptus sp.)  open forest on the crests and upper slopes of the low, steep hills that form the northern subcatchment boundary. This grades into Flooded Gum (Eucalyptus grandis) closed forest on the lower slopes and drainage lines.

The southern side of the subcatchment supports open forests of Blackbutt and Bloodwood on the crests and slopes of the steep low hills that form the subcatchment boundary.

The alluvial plain that hugs the creek line is populated by remnants of Forest Red Gum (Eucalyptus tereticornis) open forest in the upper catchment, which grades to open forests of Tea-tree (Melaleuca sp.) in the lower catchment. The area adjacent to the creek mouth supports closed forest of Swamp She oak (Casuarina glauca) and Tea-Tree (Melaleuca sp.). There are several areas of freshwater wetlands on the alluvial plain, in the area of Forest Glen. These wetlands are populated by Broad-leaved Tea-tree (Melaleuca quinquenervia). The intertidal area immediately surrounding the creek is populated by woodlands of Grey Mangrove (Avicennia marina) and Red Mangrove (Rhizophora stylosa) interspersed with saltwater grasslands.

Eudlo Creek drains the southernmost quarter of the Maroochy river. Bounded by the Mooloolah Range on its southern margin, it rises in the steep slopes of the Blackall Range, and joins the main channel of the Maroochy River in its estuary just upstream from Maroochydore, close to the mouth of Petrie Creek.

The catchment rises in the escarpment of the Blackall Range, which has a thin band of soils derived from Laterised Tertiary Basalt along the lip of the escarpment. The steep slopes of the escarpment are derived from sandstone, and this landform continues along the southern side of the catchment, forming the Mooloolah Range. The north side of the catchment is derived from Laterised Sandstone, forming the low hills that form the catchment boundary.

The drainage line has developed an area of undifferentiated freshwater alluvium of silt, clay and larger sediments immediately adjacent to the watercourse, dividing the two different parent materials on the north and south sides of the creek. The mouth of the creek is formed of Holocene windblown sand deposits. This area is subject to tidal inundation, and is mixed with riverine mud sediments.

The major land uses of the subcatchment are native vegetation, which covers approx. 45 % of the subcatchment, cropping (including sugar cane) which covers 25%, and grazing of both beef and dairy cattle, which covers 12%.  The remnant native vegetation is concentrated on the mid to upper slopes of the low, steep hills that form the boundary of the subcatchment, with very little in the riparian zone. Most of this vegetation is in small fragments, with only a small percentage in the reserve system. The second largest land use, cropping is concentrated in the mid to lower subcatchment, where the land becomes undulating, and the cropping areas are found on the ridges and crests of the low hills.  Grazing, the third largest land use in terms of area is concentrated in the upper subcatchment, mostly in the alluvial areas where the soil is of higher quality. A land use practice that utilizes only a small area, but of note, is the sand and gravel extraction operations being conducted on the alluvial plain halfway down the subcatchment. These operations have obvious implications for water quality.

The State of the Rivers report of 1992 gave Eudlo creek a wide range of ratings, from very good to highly degraded. The sections rated good to very good amount to 35 % of the total stream length, with the majority being in the wetlands in the Forest Glen area and in the headwaters in the Landers Shoot area.  However, the remainder of the creek was degraded to some degree, especially in the stability of the bed and bars, and in the general shallowness of the pool environments. 70% of the riparian vegetation was rated as very poor.

The major land uses within the subcatchment are native vegetation, crops and sugar cane. Native remnant vegetation occupies nearly a third of the subcatchment area, and occurs mostly on the surrounding hills. Cropping, which occupies one quarter of the subcatchment area, occurs mostly in the upper reaches, sugar cane, which occupies 14% of the area, is grown exclusively on the floodplain of the lower subcatchment, near the confluence with Petrie Creek.

Technically a tributary of Petrie Creek, Paynter Creek has its headwaters in the Blackall Ranges near the town of Montville. It discharges into Petrie Creek 2 km from the Maroochy River.

The headwaters of Paynter Creek begin in the Laterised Tertiary Basalt of the Blackall Range. This landform quickly gives way to Sandstone in the upper slopes of the range. This in turn gives way to Laterised Sandstone on the foothills of the range and the valley floor. The drainage line has developed a thin ribbon of Quaternary Alluvium of gravel, sand, silt and clay.

The subcatchment becomes constricted by the fringing low hills of Laterised Triassic to Jurassic Lands borough sandstone halfway along its length. The riparian zone is dominated by a system of semi-continuous valley flats and alcoves. The subcatchment opens out briefly at several points, where small alluvial plains are formed. A continuous alluvial plain develops toward the confluence with Petrie Creek, which joins with that creek,s alluvial plain.

Remnant vegetation covers less than one third (28%) of the subcatchment, none of which is contained in State Forests or National Parks. The vegetation is closely linked to landform. The upper slopes and crests of the low steep hills largely support open Blackbutt (Eucalyptus pilularis) forest interspersed with pockets of gallery forest and palms sheltering in protected areas.

This vegetation type becomes mixed with Bloodwood stands in the upper subcatchment. The riparian zones in the upper catchment support areas of subtropical rainforest; whilst in the lower subcatchment the alluvial plain supports remnants of melaleuca open forest. Near the confluence with Petrie Creek, there are several patches of remnant mangroves, predominately Grey Mangrove (Avicennia marina) inhabiting the creek margins.