1.1.2.1 Physical geography


The Clarence-Moreton bioregion spans several coastal river basins in north-east New South Wales, and south‑east Queensland, and forms an area of about 24,292 km2, approximately 9500 km2 of which is in Queensland. In New South Wales it contains much of the Clarence and Richmond river basins, while in south‑east Queensland it covers the mid and upper parts of the Logan-Albert Rivers, Bremer River, Lockyer Valley, and parts of the Brisbane river basin (Figure 21).

The bioregion covers a large area, and spans multiple climate zones. The climate of the bioregion falls within the temperate and subtropical climate groupings (ABARES, 2013). It contains large areas of steep ranges and forests. The bioregion contains large river systems (e.g. Clarence and Richmond Rivers in New South Wales), and there are extensive river valley flats, floodplain swamps and wetlands in these areas. Grazing and cropping is undertaken in the large valley floor areas. There are also smaller areas of intense horticulture in locations such as the Alstonville plateau near Byron Bay in New South Wales. The Lockyer Valley in south‑east Queensland supports a large irrigated cropping and vegetable industry.

There are extensive areas of wetlands, with 31,000 ha in the Richmond river basin, and 43,000 ha mapped in the Clarence river basin (DLWC, 2000). The extensive wetlands in the lower Clarence valley are supplied by groundwater and local runoff (except during large flood events) (Auld, 1998: cited by DLWC, 2000).

Figure 5

Figure 5 Surface elevation, major rivers and wetlands of the Clarence-Moreton bioregion

1.1.2.1.1 Physiographic regions

Physiographic regions are defined in terms of landform characteristics and geology, and are the basic geomorphological subdivisions for Australia (Pain et al., 2011). The mapping criteria relate to landform attributes, and the resultant mapped units can be described in terms of landform, underlying geology, regolith and soils (Pain et al., 2011).

The bioregion is part of the New England-Moreton Uplands Province, within the broader Eastern Uplands Division. This diverse area covers parts of the six physiographic regions, which are listed in Table 2 (Pain et al., 2011), and shown in Figure 6.

Table 2 Physiographic regions within the Clarence-Moreton bioregion


Region

Region name

Region description

10503

Moreton Lowland

Lowland on weak sedimentary rocks, with prominent volcanic plugs, includes dune islands

10504

Toowoomba Plateau

Basaltic plateau terminating southeast in dissected volcanic pile (Mount Warning)

10507

Clarence Fall

Dissected plateau margin on granite and metamorphic rocks

10508

Clarence Lowlands

Coastal lowlands on weak sedimentary rocks, with littoral and alluvial plains

10513

Bunya-Burnett Ranges

Mountain ranges, rugged and dissected on granitic and metamorphic rocks in east, broader uplands and upland basins, partly on sedimentary rocks, in west

20205

Condamine Lowlands

Undulating clay lowlands on siltstone and low sandstone hills; floodplains

Source data: Pain et al. (2011)

Figure 6

Figure 6 Physiographic regions in the Clarence-Moreton bioregion

Source data: ASRIS (2013)

1.1.2.1.2 Soils and land capabilities

As expected in such a diverse area containing steep mountains, river valleys and coastal areas, there is wide variability in soil type across the Clarence-Moreton bioregion. Soil Orders (Australian Soil Classification: ASRIS (2013)) are shown in Figure 7.

In New South Wales there are several large soil monitoring units (SMUs) in the bioregion (DECCW, 2010a). These include Clarence Sodic Soils around Grafton (Kurosols), Alstonville Plateau (Ferrosols), Casino Alluvials along the Richmond Valley (Vertosols), and North Coast Acid Sulfate Soils (Hydrosols) mainly in the lower parts of the Clarence and Richmond floodplain. In Queensland, the Lockyer, Bremer and Warrill valleys have large areas of alluvial plains (Vertosols) with surrounding undulating hills (Sodosols).

Figure 7

Figure 7 Australian Soil Classification (ASC) Soil Orders and Acid Sulfate Susceptible Soils of the Clarence-Moreton bioregion

Source data: ASRIS (2013) and DECCW (2010a)

There are extensive areas of acid sulfate soils scattered across the southern (New South Wales) parts of the bioregion (see Figure 7). Acid sulfate soils are typically low-lying coastal soils which were formed in a marine environment. The drainage of these soils can lead to their exposure and can produce sulfuric acid which reduces pH of the soil, associated water bodies and result in damage to ecosystems (DECCW, 2010a). Table 3 shows the distribution of acid sulfate soils in the Upper North Coast of New South Wales. The Queensland part of the bioregion is mostly away from these coastal areas, although there are small scattered areas of acid sulfate soils in this part. The largest area of acid sulfate soils in the bioregion is in New South Wales in the Clarence Valley downstream of Grafton, and there are also large areas in the lower Richmond Valley (Figure 7). These New South Wales SMU ‘North Coast Acid Sulfate Soils’ is assessed as being in fair (declining) condition (DECCW, 2010a) and with only a poor rating for ‘Land management with capability’ (DECCW, 2010b).

Table 3 Distribution of acid sulfate soils in the Upper North Coast of New South Wales


River basin

Estimated area with underlying acid sulfate soils

Tweed

9700 ha high risk

2000 ha low risk

Brunswick

3193 ha high risk

10,000 ha low risk

Richmond

34,000 ha high risk

34,000 ha low risk

Clarence

53,000 ha high risk

Source data: DLWC (2000)

1.1.2.1.3 Land cover

The Clarence-Moreton bioregion has large areas of woody vegetation (both closed and open) (Figure 8). These dominate the landscape in the steeper and upland parts of the bioregion, but are also widespread throughout the bioregion. The Clarence-Moreton bioregion also contains large areas of cropping and grazing land, which tend to be focused along the flatter river valley areas. The northern part of the Clarence-Moreton bioregion has a greater amount of scattered woody vegetation than the southern part, and also has a lower rainfall.

Figure 8

Figure 8 Land cover in the Clarence-Moreton bioregion

Source data: Geoscience Australia (2013)

Last updated:
23 March 2016
Thumbnail images of the Clarence-Moreton bioregion

Product Finalisation date

28 May 2014