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GEOMORPHOLOGY AND SURFACE MATERIALS: SPEEWA

J.D.A. Clarke, V. Wong, C. Pain, H. Apps, D. Gibson, J. Luckman and K. Lawrie

CRC LEME Open File Report 202

December 2008

© CRC LEME 2008

CRC LEME is an unincorporated joint venture between the Australian National University, University of Canberra, Australian Geological Survey Organisation and CSIRO Exploration and Mining.

Headquarters:- CRC LEME C/o CSIRO Exploration and Mining, Private Bag 5, Wembley 6913, Western Australia.

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Address and affiliation of authors

J.D.A. Clarke, V. Wong, C. Pain, H. Apps, D. Gibson, J. Luckman and K. Lawrie Cooperative Research Centre for Landscape Evolution and Mineral Exploration c/- Geoscience Australia PO Box 378 Canberra ACT 2601

DISCLAIMER

The user accepts all risks and responsibility for losses, damages, costs and other consequences resulting directly or indirectly from using any information or material contained in this report. To the maximum permitted by law, CRC LEME excludes all liability to any person arising directly or indirectly from using any information or material contained in this report.

© Cooperative Research Centre for Landscape Evolution and Mineral Exploration

2008

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EXECUTIVE SUMMARY

Over the past 15 years more than 40 airborne electromagnetic (AEM) surveys have been acquired for groundwater and salinity mapping and natural resource management in Australia. Most of these have been in floodplain or other low relief landscapes. Several projects have successfully demonstrated how AEM surveys can be used to underpin a wide range of salinity management strategies, and a review of salinity mapping methods in the Australian context by Spies and Woodgate in 2004 recommended that AEM systems were the most appropriate for mapping salinity in Australia’s landscapes.

In early 2007, an airborne electromagnetic (AEM) survey was acquired along a 450 km reach of the River Murray Corridor (RMC) in SE Australia. This aim of this survey, carried out under the auspices of the Australian Government’s Community Stream Sampling and Salinity Mapping Project (CSSSMP), and managed by the Bureau of Rural Sciences (BRS), is to provide information vital for addressing salinity, land management and groundwater resource issues. The study area stretches from the South Australian border eastwards to Gunbower in Victoria. A total of 24,000 line km of AEM data were acquired. The survey area encompasses iconic wetland areas, national and state forest parks, and areas of irrigation and dryland farming.

Within the RMC project area key land management questions include (1) what is the impact of irrigation on the floodplain, river and groundwater system?; (2) what is the distribution of saline groundwaters where these have the potential to impact on the floodplain and river?; (3) where are the salt stores in the unsaturated zone within the floodplain?; (4) what is the potential for salt mobilisation during Living Murray inundation actions and natural flood events; (5) what are the drivers for floodplain health with respect to groundwater processes?; (6) is there leakage from salt disposal infrastructure?; and (7) what is the extent of losing and gaining effects along different reaches of the river system?

To address many of these questions, maps of the distribution of salt stores, saline and fresh groundwater and the hydraulic properties of soil and regolith materials in the shallow sub-surface are required. These are required to provide a 3-D understanding of how salt stores and saline groundwaters connect to the surface waterways and land surface. Sub-surface interpretations in the survey areas are hampered by a low density of useful borehole data in the floodplain in particular, and by a paucity of soil and landscape surface mapping at appropriate scales throughout the project area. New maps of surface materials, and a new geomorphic understanding of the RMC project area is required to constrain the interpretation of the AEM surveys, and address the land management questions.

This report documents the results of new surface materials mapping in the Speewa survey area, and the methodology used to produce the maps. Because of the small size of the area and the similarity to adjacent areas, no samples were collected.

The landforms of the Speewa area are very similar to those found immediately downstream at Nyah. The floodplain is only very slightly inset into the Mallee landscape, and the Speewa area is there the inset valley becomes indistinguishable from the rest of the riverine plain. Is is also the area in which the influence of the terminal influence of the north flowing fans from the southern Victorian highlands become evident.

The surrounding Mallee landscape is covered by dunes of Woorinen Sand, some of these occur on the floodplain as well.

The floodplain is smooth, and composed of silts ands clays. Levees are only locally present. Anabranches are common. Saline takes are present along the southern part of the area and

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are interpreted as indicating the presence of shallow discharging groundwaters along the distal parts of the north-flowing fans.

Ken Lawrie Project Leader

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ABBREVIATIONS

ACRES Australian Centre for Remote Sensing AEM Airborne Electro Magnetics ASTER Advanced Spaceborne Thermal Emission and Reflection Radiometer BC Blanchetown Clay BRS Bureau of Rural Sciences CF Coonambidgal Formation CMA Catchment Management Authority CRC LEME Cooperative Research Centre for Landscape Environments and

Mineral Exploration DEM Digital elevation model

DSE Department of Sustainability and Environment GA Geoscience Australia LIDAR Light Detection and Ranging MDBC Murray-Darling Basin Commission MS Monoman Sands PS Parilla Sands RGB Red, Green, Blue RMC River Murray Corridor RMT River Murray Trench SF Shepparton Formation SPOT Satellite Pour l'Observation de la Terre STRM Shuttle Radar Terrain Model VNIR Very near infrared radiation WF Woorinen Formation XRF X-Ray Fluorescence

XRD X-Ray Diffraction

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CONTENTS

1 INTRODUCTION ............................................................................................................ 1 2 PREVIOUS STUDIES ..................................................................................................... 1 3 LAND MANAGEMENT QUESTIONS .......................................................................... 2 4 METHODOLOGY ........................................................................................................... 3

4.1 Data Availability and Quality .................................................................................. 3 4.1.1 Satellite imagery .................................................................................................. 3 4.1.2 Digital Elevation Models ..................................................................................... 3 4.1.3 Gamma-ray data................................................................................................... 3

4.2 Image Processing ..................................................................................................... 3 4.3 Fieldwork ................................................................................................................. 4

5 RESULTS......................................................................................................................... 5 5.1 Regolith Landform Units ......................................................................................... 5 5.2 Vegetation ................................................................................................................ 6 5.3 Hydrogeological issues ............................................................................................ 7 5.4 Relevance to land management questions................................................................ 7

REFERENCES.......................................................................................................................... 9

LIST OF APPENDICES

APPENDIX 1. ASTER data and interpretation....................................................................... 10 APPENDIX 2. SPOT data and interpretation.......................................................................... 12 APPENDIX 3. DEM data and interpretation........................................................................... 14 APPENDIX 4. Gamma-ray data.............................................................................................. 16 APPENDIX 5. Surface materials map..................................................................................... 17

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LIST OF FIGURES

Figure 1. The Speewa study area............................................................................................... 1

Figure 2. Conceptual model (cross-section) and geophysical targets in the Speewa area:........ 2

Figure 3. Digital elevation coverage in the Speewa area........................................................... 4

Figure 4. View across a typical cleared floodplain landscape in the Speewa study area. ......... 4

Figure 5. Representative landscape elements of the Speewa region. ...................................... 5

Figure 6. Floodplain architecture of the northeastern part of the Speewa area ......................... 6

Figure 7. Oblique LIDAR DEM showing low relief drainage channels on the floodplain. ...... 7

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1 INTRODUCTION

This report covers the preliminary interpretation of the surface materials and landforms of the River Murray Corridor (RMC) at Speewa, west of Swan Hill. This is based largely on the interpretation of multiple sets of remotely sensed data and two days of field work in May and June 2007. Due to the small size of the study area, no samples were collected. However, remotely sensed data indicated that landforms and surface materials in this area were similar to those described upstream in the Boundary Bend to Nyah reach (Clarke et al. 2007a) and downstream in the Barr Creek-Gunbower reach (Clarke et al. 2007b). This was confirmed by field validation.

Figure 1. The Speewa study area

2 PREVIOUS STUDIES

Previous studies by Churchward (1961, 1963a, b, c) have placed the soils in a regional context. However, these studies are primarily focussed on aeolian soils predominantly in

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NSW, and only briefly examined those occurring on the floodplain. Fried (1993) discussed the Swan Hill area in the context of the origin of late glacial maximum sinuous streams. A compilation of drilling results for the Murray River floodplain by Thorne et al. (1991) provides a useful regional stratigraphic and groundwater context. Cautious extrapolation from the study by Thorne et al. (1991) to the Speewa area from Nyah is possible as the nature of the fluvial sequence is similar.

3 LAND MANAGEMENT QUESTIONS

Speewa is a high point contributor of salt to the Murray River. High salt loads may be mobilised from the adjacent irrigation areas into Barr Creek (target 1) and into the Murray River. Four land management questions were posed by Lawrie (2006) in response to the requirements of the North Central Catchment Management Authority (CMA), listed below.

1) What are the salt loads to the River Murray? This question refers to Target 1a in Figure 2, and can be answered by the AEM data, with little or no input from the geomorphology or the surface materials mapping component in this report.

2) How can we better manage these salt loads? This report will help in the identification of the salt stores and actual or potential migration pathways (Target 1b in Figure 2). In conjunction with the conductivity measurements obtained in the AEM data, these data will help inform the decision-making process, particularly those related to salt load.

3) How can we achieve better understanding of groundwater interactions? The geomorphic and surface materials map will identify connections between groundwater and the landscape, particularly when combined with AEM and borehole data. Targets 2a and 2b (Figure 2) are potential flush zones.

4) How can water trading decisions be better informed? The integration of the AEM and borehole data, surface and subsurface material characterisation, and geomorphology and vegetation mapping can assist in developing better informed frameworks for water tracing.

A conceptual model of the floodplain structure and the geophysical targets relating to the land management questions is shown in Figure 2 (Lawrie 2006).

SF

SF CF

Barr Creek 1a

1a1b

1a1b

Irrigation Irrigation

2b

2a

2b

Figure 2. Conceptual model (cross-section) and geophysical targets in the Speewa area: CF = Coonambidgal Formation, SF = Shepparton Formation (Lawrie 2006). Dark grey boxes define targets that have very high conductivities, white areas have moderate-high conductivities, and light grey boxes identify target areas with low conductivities. Numbers 1-2 are geophysical targets identified in the land management questions.

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4 METHODOLOGY

4.1 Data Availability and Quality

4.1.1 Satellite imagery

The primary satellite images used to compile surface polygons were those from ASTER and SPOT. Landsat images were used for comparison and infill, but were not generally interpreted as SPOT and ASTER coverage was usually adequate for the project area. ASTER images were used to map total surface variability (including soil mineralogy, moisture and vegetation; Appendix 1), while SPOT images were used to compile vegetation maps (Appendix 2).

Three ASTER scenes with 15m resolution covered the Speewa area. These scenes were the available scenes and were acquired from ACRES in GA with two dated 09 January 2001 and one dated 05 March 2001. The ASTER scenes were displayed as a composite RGB images using the visible and near infrared radiation (VNIR) bands 3, 2 and 1. One pan-sharpened pseudo natural colour SPOT scene with 2.5 m resolution dated 25 December 2004 was also acquired from GA. Bands 3, 2 and 1 were displayed in a composite RGB image. The Landsat-7 ETM ortho-corrected image with 30 m resolution was acquired on the 04 Feb 2002.

4.1.2 Digital Elevation Models

High resolution airborne LIDAR digital elevation model (DEM) coverage was available for part of the area (Figure 3). The LIDAR data were supplied by MDBC in ArcGRID format with 69 2 km x 2 km tiles at 1 m resolution in the Speewa area. The tiles were spliced together as a mosaic in ArcInfo and resampled to 2 m to minimise file size.

The Shuttle Radar Terrain Model (SRTM) was used as the base where other DEM data were not available. The SRTM was used as supplementary data only, as the spatial and vertical resolution are too low and the noise level too high at a scale of 1:25 000.

The LIDAR DEM was the basis of interpretation where it was available. The lower resolution DEM, supported by the ASTER and gamma-ray data, were used to extrapolate the distribution of units defined on the LIDAR DEM, guided by experience gained elsewhere in the River Murray Gorge (MRG). The final compilation is shown in Appendix 3.

4.1.3 Gamma-ray data

The gamma-ray data are contained in Appendix 4.

4.2 Image Processing

The ASTER level 1B scenes were supplied by ACRES in .hdf format, corrected for crosstalk, caused by signal leakage from band 4 into adjacent bands 5 and 9, and imported into ERMapper. Importing was carried out in three steps with bands of similar resolution i.e. VNIR bands 1-3 at 1 5m resolution, SWIR (shortwave infrared radiation) bands 5 – 9 at 30 m resolution and TIR (thermal infrared radiation) bands 10 – 14 at 90 m resolution. All bands were rotated and corrected for dark pixels and radiance calibration, which included rescaling of digital values to observed top of atmosphere radiance values. The resultant ERMapper datasets were displayed as composite RGB images.

SPOT 5 images were processed by Geoimage Pty Ltd for the NSW Department of Infrastructure Planning and Natural Resources and supplied by GA. Processed LANDSAT 7 data was supplied following ACRES Quality Assessment.

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Figure 3. Digital elevation coverage in the Speewa area.

The ASTER, SPOT and LIDAR images were printed at a scale of 1:25,000 and interpreted by mapping unit boundaries onto a registered stable transparent overlay with mapping pens. The interpreted line work was digitally scanned and the polygons attributed. The finished images were then printed out for verification. Interpretation of the ASTER and SPOT images was limited by the extensive land clearance that has been carried out in the area. Therefore, the images were only relevant to land use, rather than the associations between vegetation and soil type, surface hydrology and geomorphology. Therefore, interpretation of the landscape was based primarily on the LIDAR DEM and other DEM datasets.

Typical landscapes in the Speewa region are shown in Figure 4 and Figure 5.

Figure 4. View across a typical cleared floodplain landscape in the Speewa study area.

4.3 Fieldwork

Several days were spent in the area during two field trips in May and June 2007. Fieldwork was undertaken to validate mapped polygons and compare features with those observed up-

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and downstream in the Boundary Bend-Nyah and Barr Creek-Gunbower reaches of the river, respectively (Clarke et al. 2007a, b). Soils were not sampled in this reach due to the similarity to those sampled in adjacent areas and time constraints.

5 RESULTS

5.1 Regolith Landform Units

The RMG that constrained floodplain sediments downstream disappears in the Speewa reach. The floodplain merges with the surrounding area along a poorly defined margin instead of occurring as a constrained floodplain within a distinct topographic feature.

Figure 5. Representative landscape elements of the Speewa region. Top left: Speewa ferry, showing a smooth floodplain and absence of levees. Top right: saline lakes in the south west corner of the Speewa survey area. Bottom left: view across the north eastern section of the Speewa survey area from the top of a large lunette. Bottom right: view looking up slope of large (20 m high) sand and minor clay lunette in north east corner of the Speewa survey area.

Marginal areas are characterised by quartz dunes, salt lakes and clay pans, and lunettes which are encroached upon by the modern floodplain, and may be underlain by the Shepparton Formation. These elements have been mapped as the alluvial terrace. The modern and ancient lake systems and their lunettes are part of the groundwater discharge zone developed in the distributary system of rivers draining the southern Victorian uplands, such as the Loddon River (Macumber 1968). Many of these lake systems are no longer expressed in the landscape, with their former presence is indicated by lunettes on the floodplain An extremely large lunette system (> 5 km long and 20 m high) is present in the extreme east of the Speewa survey area, north of Swan Hill (Churchward 1963c). This is shown in Figure 6.

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The floodplain is smooth and traversed by the main channel of the Murray River and a number of anastomosing channels including Speewa Creek. The floodplain soils are similar to the clay textured soils described from the southern section of the Boundary Bend-Nyah reach (Clarke et al. 2007a). Very low relief channels visible in the DEM but impossible to see on the ground cut the floodplain (Figure 7). These may be formed by drainage of water after floods.

The main channel of the Murray sustains flow with a sandy base, while the anabranches are stagnant, sometimes dry and lined with clay. The channels of the Murray River and its anabranches are fixed rather than meandering. As a result the floodplain and channel banks are marked by vertical rather than lateral accretion and therefore, partly flanked by levees (Figure 6).

Figure 6. Floodplain architecture of the northeastern part of the Speewa area, showing well developed levees, a leveed distributary channel of the floodplain, and the relict lunette.

5.2 Vegetation

Most of the native vegetation in the survey area has been cleared primarily for agriculture. The native vegetation that remains is composed mainly of River Red Gums (Eucalyptus camaldulensis) and found predominantly on the banks of the Murray River and Speewa Creek. Prior to clearance, it is likely that the native vegetation was composed of River Red Gum open forests on the floodplain levees and open forests of River Red Gums, open woodlands of mixed River Red Gum and Black Box (E. largiflorens) trees and woodlands of Black Box trees on the floodplain.

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Figure 7. Oblique LIDAR DEM with strong vertical exaggeration showing low relief drainage channels on the floodplain.

5.3 Hydrogeological issues

We predict that the Speewa area will consist of three main units in terms of the hydrogeology, which are the channel system of the Murray River, the floodplain, and the older units of the terrace.

The main channel of the River Murray is the main recharge for the shallow aquifers formed by the basal sands of the floodplains. Local recharge through wetting of surficial clays can occur in the anabranches of the Murray River, such as Speewa Creek. Recharge of the basal sands aquifers from these smaller channels is not expected due to the presence of the clay seal. Similarly, the floodplain is also largely impervious to recharge due to the presence of the clay seal.

The terrace is most likely composed of the Shepparton Formation, and is largely impermeable to vertical recharge due to its similarity to the modern floodplain. Lateral recharge is likely to occur from the south from the north draining rivers, leading to groundwater discharge in the clay plans and other dry lake features. Localised perched aquifers are predicted to occur beneath the sand dunes.

5.4 Relevance to land management questions

As previously noted, four land management questions were identified by the CMAs for the Speewa region.

1) What are the salt loads to the River Murray? This question cannot be answered by the geomorphology or the surface materials mapping in this report.

2) How can we better manage these salt loads? Geomorphic mapping has indicated that salt loading will most likely occur from encroachment of regional groundwater flows from the south impinging on the basal sand aquifer of the Murray floodplain. It is possible that higher salt loads occur in the older alluvial sediments of the terrace and

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in the old lake sediments, which will be confirmed by the AEM results. This knowledge will affect management plans for saline water intrusion.

3) How can we achieve better understanding of groundwater interactions? The geomorphic data indicates that it is unlikely that a connection between the land surface and the aquifer occurs, either from abandoned channels or rainfall across the floodplain. Recharge is most likely to occur from loss from the Murray River or encroachment from the south from the Loddon Fan.

4) How can water trading decisions be better informed? As previously noted, the integration of the AEM and borehole data, surface and subsurface material characterisation, and geomorphology and vegetation mapping can assist in developing better informed frameworks for water tracing.

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REFERENCES

Churchward, H.M. 1961. Soil studies at Swan Hill, Victoria, Australia I. Soil layering Journal of Soil Science, 12(1), p.73-86.

Churchward, H.M. 1963a. Soil studies at Swan Hill, Victoria, Australia. II. Dune moulding and parna formation. Australian Journal of Soil Research 1(1) 103 – 116.

Churchward, H.M. 1963b. Soil studies at Swan Hill, Victoria, Australia. III. Some aspects of soil development on aeolian materials. Australian Journal of Soil Research 1(1) 117 – 128.

Churchward, H. M. 1963c. Soil studies at Swan Hill, Victoria, Australia IV. Groundsurface history and its expression in the array of soils. Australian Journal of Soil Research 1, 242-255.

Clarke, J., Wong, V., Pain, C., V., Apps, H., Gibson, D., Luckman, J., and Lawrie, K. 2007a. Geomorphology and Surface Materials: Boundary Bend to Nyah. CRC LEME Restricted Report 260R.

Clarke, J., Pain, C., Wong, V., Apps, H., Gibson, D., Luckman, J., and Lawrie, K. 2007b. Geomorphology and Surface Materials: Barr Creek to Gunbower Island. CRC LEME Restricted Report 264R.

Fried, A.W. 1993. Late Pleistocene river morphological change, southeastern Australia: the conundrum of sinuous channels during the Last Glacial Maximum. Palaeogeography, Palaeoclimatology, Palaeoecology, 101(3-4), p.305-316;

Lawrie. K. 2006 (comp.) Report by technical working group chair on proposed River Murray corridor (South Australian border to Gunbower) Victorian AEM mapping project. CRC LEME Restricted Technical Report.

Macumber, P.G. 1968. Interrelationship between physiography, hydrology, sedimentation, and salinization of the Loddon River Plains, Australia. Journal of Hydrology 7, 39-57.

Thorne, R., Hoxley, G., and Chaplin, H. 1991. Nyah to the South Australian Border Hydrogeological report. Rural Waters Commission of Victoria, Investigations Branch Report 1988/5, 372p.

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APPENDIX 1. ASTER data and interpretation

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Surface properties map interpreted from ASTER data

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APPENDIX 2. SPOT data and interpretation

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Vegetation map interpreted from SPOT data

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APPENDIX 3. DEM data and interpretation

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Landforms interpreted from DEM data

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Landforms

Narrow drainage channel

DESC, LANDFORMBillabong

Channel

Channel (abandoned)

Salt lake or clay pan

Lunette

Floodplain (smooth)

Dune on smooth floodplain

Floodplain levee

Alluvial terrace

Dune on terrace

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APPENDIX 4. Gamma-ray data

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APPENDIX 5. Surface materials map