r,; .. ND TJNITS Ob' THE BOEROIOOL.t\

TOIV1'ISHIP AREA.

1974

by

D.F. Howe and A. C;z8chor0wski

1J;:md Conc:ervation. Section, AnimaJ. I'1o:ustry and Agrjculture Branch, Dppartmsnt of the N0rthern Territory, lJ.~ m.JI~;, N. '11.

ACKNOWLEDGEMENTS

The authors wish to express their sincere thanks to l-lr. P.J. McLeod

for his assistance during the field work and to Mr. C.R. Dunlop for his

advice on plant identification. Map production would not have been

possible without the patient and accurate work performed by June Brett

of the Department of Services and Property. The authors are also in­

debted to IViessrs. J.N. Aldrick and C.S. Robinson for their cons+;ructivf->

criticism and assistance in the preparation of the report.

1.

CONTENTS

1 •

2.

5.

6.

7.

Introduction

Description of Survey Area

Summary of Umi tations to Land Use

sons

Vegetation

Schematic Cross Sections Showing Spatial Relationships of Land Units

Land Unit Descri.ptions

1 •

3.

5.

6.

Location Map

M:-:cjor landscape divisions t roads t. and aerial r~oto ruYlS in survey area

Diagramatic representation of survey area

SpaUal relationship of land units of the Borroloola Basin

Spatial relationships of land lmi ts of the MesC'. 7,one

Snatial relationships of land units of the Coastal pia ins

References

Appendix

1. Sui tabiJ. i. ty for Urban Development

2. Agricultural Potential

S10pe Categories

Plant Species List

5. Soil Descriptions of Representative Profiles

Page

2

8

11

21

26

3

4

5

26

26

26

54

56

59

61

2.

10 INTRODUCTION

This survey of the Borroloola township area was carried out at

the request of Urban Development and Town Planning Branch, Department

of the Northern Territory. The aim was to provide information

primarily on soils, vegetation and land forms and to indicate any

limitations associated with land resources which might restrict develop­

ments accompanying urban expansion.

The area considered in this report extends about 7.5 km to the

east and west of the existing general store, then 7 km to the north

and about 5 hu south.

Land units

The level of definition chosen to express the field data was the .

land unit. This has been described as "an area of land which exhibits

an essentially uniform pattern on aerial photographs~t. (Aldrick and

Robinson, 1970). Land units depict areas which have similar soils,

vegetation,· and topography.

Adequate aerial photography of the region was available, this

being McArthur River 1966, RCS at 1:16 400 scale. An excellent

regional description was also available in l~cArthur River Land System

Survey" by Scott and Speight, 1966. The scale of their map, however,

at 1:100 000, was not adequate for the detailed study which was needed

to provide the information requested. Nevertheless, this report

Figure I

N

t

Location map

DARWIN

\KATHERINE

BORROLOOLA

TENNANT CREEK

ALI CE SPRINGS

o 300 SCALE KILOMETRES I

Ji"IG.2.

t N

( .. \ \ 1.1.)

Major landscape divisions, roads, and aerial

photo runs in survey area.

/ / /

LJ !·If.)f'a zone

1 1 Coastal plains

FIG. 3.

s.

Diagramatic representation of survey area.

Major Landscape Divisions

(i) 0 Borroloola basin

(li) U f.lesa zone

(iii) 0 Coastal plains

1\.\.Of-\€::-rR,.€.:; ( o..PPfll""x.) o I 2.. 3 4-R I

, -;

;; .'

6.

provided a very good framevlOrk for classifying the soils and

vegetation and for identifying landforms.

It should be noted that land unit mapping from aerial photos re­

lies upon the existence of native vegetation over the area as an ex­

pression of the net climatic and soil influences which have operated

on different areas. The survey area lends itself very well to this

method and, generally speaking, the facets of the landscape or land

units were delineated by quite abrupt boundaries.

It should be realized that the accompanying map is not a soils

mar. 1(:nd units delineate essentially similar Clreas and onl:," in certa n

instances are areas defined that are perfectly uniform with regard to

soil type. The range of soil types in a land unit is however, greatly

reduced. The variation that can occur is listed in the expanded key

in this report. Final definition of soil type can only be achieved

with considerable input of time and effort and this cannot always be

justified where broad areas are being surveyed.

Data collection and presentation

The technique used entailed -

(i) pre-interpretation of the aerial photos under stereoscopic

examination, and selection of sites for sampling;

(ii) location of sites in the field and sampling of soils, landforms

and vegetation;

(iii) determining the correlations in the field data and

finalizing the land unit boundaries on aerial photos; and

(iv) production of a map. In this instance a direct traCing from

the photos was taken because no suitable base maps for pro­

jection were available.

8.

2. DESCRIPTION 01" SURVEY AREA

Three of the landscape divisions of Scott and Speight can be

iden tified in the area. These are :

(i) Borroloola Basin

(ii) Mesa Zone

(iii) Coastal Plains

Figure 2 shows where these divisions occur in the survey area.

Figure 3 is a schematic block diagram shm-ling the relationship betwetm

,.:le tr~ree landscape divisions.

(i) Borroloola Basin

This is thought to be the result of fluviatile and lacustrine de­

position behind a barrier formed by what is now the McLeod Ran~e. Sub­

sequently, the McArthur River appears to have cut down through the rang~

and has drained the basin. Because of the difference in elevati...)n of

the river and the plain surface, 3.ctive erosion appears to be a feature·

of the river frontage.

Soils on the plain are typically cracking clays with some areas of

earthy sands which appear to overlie the clay in a relatively tbin,

patchy sheet. The sandy soils near the township are higher and better

drained than the clay soils. Some of the sandy areas on the plain

resemble old levees along drainage paths which posBibly still function

in times of peak flooding. Several swampy depressions occur which

could indicate the position of ancient river courses.

(ii) Mesa Zone

This is represented near Borroloola by the McLeod Ranges. These are

Upper Proterozoic Sandstones, moderately folded and usually tilted.

Erosional remnants of the sub-horizontally bedded Cretaceous siltstones

and sandstones occur as mesas scattered over the older rocks and these

usually have relict laterite cappings. This regicn is typically

me,:Jer&tely steep to ~'ugged, and soj 1 development i3 minimal. l'c)c}:(,ts

of sandy wash occur in drainage lines and on lower footslopes. Some

small sand plains occur on the more extensive structural plateaux.

(iii) Coastal Plains

The soil material on the coastal plains division is generally coarser

than thE.. t of the Borroloola Basin. This is probably due to de­

position from a higher velocity current and in fact much of the surface

shows signs of ancient channels and terraces downstream of and

radiating from the gap in the McLeod range where the rjver emerges.

This area is considered to be less prone to flood~ng that the flood

plain of the Borroloola Basin - quite possibly due to the gap in the

ranges acting as a "flood relief valv8".

10.

There is also 8. gently nnd.ulating sand. plain i.n the north of the

8 11rvPy RreH on the Coastal Flai.~s which is consi d.ered to be formed

from colluyi2.1 H''l,sh i'r0m sandst.one of the Mesa Zone. This is higher

::ODd better. (lra.i~ed than the dominantly sandy riverine pl.ai.n.

11.

3. SUMNARY 01<' LIMITATIONS TO LAND USE

Specific limitations to the potential of each land unit are given

in the expanded Key (page 27) and also in appendices 1, 2, and 3. A

few generalizations can, hOivever, be made.

(i) Borroloola Basin

(a) All land units forming the Borroloola basin (6a, 6ab, 6b1,

6b2, 6c, 6d, 6e, 6f, 7a, 7b, 7c) are subject to flooding

in the long term. The existing township site happens to

be on one of the higher portions of tho floodpla: i1, ~.:.r,d L,

flooded at a lOi'ler frequency. ',-jater Resources Branch has

determined the extent and probable frequency of the flood­

ing in the imm.ediate vicinity (Report by K.N. Hug, 1~71j).

At the time of preparing this report, the authors are un­

aware of any intended flood control works upstream in tho

NcArthur River. If the present townsite is to be developed,

this should only proceed if investigations bear out the

possibilities for adequate flood control.

Isolation of the present site during times of flood appears

to be unavoidable in the absence of flood control works.

12.

(b) If township development on the present site·continues, it

should be noted that natural erosion of the badland areas

(6e, 6f) is likely to continue, in the absence of consider­

able soil conservation inputs.

(c) Soil depth does not appear to be a limitation although the

clay soils would have a very low hydraulic conductivity

when wet. It is anticipated that the clay soils would be

unsuitable for septic effluent filter fields.

(ii) :filesa Zone

(a) Rugged areas (1b, 2a, 2b, 2c) have obvious limitations

from the engineering viewpoint. Table V (page 61) in

Appendix 3 shO'i1S the relative "ruggedness" of all the land.

uni ts above.

(b) Similarly, the structural plateaux (1a, 1b) are fragmented

and isolated by areas of rugged terrain.

(c) The undulating plains on structural plateaux (3a, 3b) offer

slightly better potential but are, once again, somewhat re­

stricted by their shape and size. Gravel stripping for

road filIon 3b >vill be a problem if development on these

areas is considered.

( d) Some consolation can be had from the fact tliat there is

little shortage of material for filling in the area. This,

however, could be difficult to extract in SOi;le instances

due to the hardness of some of the rock.

(e) Either Rocky Creek or the McArthur River mus~ be crossed

to reach areas vii th development potential in this landscape

division.

(iii) Coastal Plains

(a) Trio s'lnd plain area designated 4a offerf;; good prosr:c:~t.8

apart from the fact that Rocky Creek must be crossed to

reach it. However, it should be noted that all areas with

no risk of flooding are either on the opposite side of Rocky

Creek from the present store and townsite or else occur over

the T-1cArthur River.

(b) Land unit 5a1 has better potential Tor development than the

remaining land units in this division although peak flooding

would cause isol~tion at least.

(c) 'l'he other land units, 5a2, 5b, 5c and the river front

assemblage 7a, 7b, 7c, suffer from limitatior.s similar to

those affecting the Borroloola Basin land unjts.

4. SOILS

Soils in the survey area have been classified according to depth,

texture, gravel content and principal profile form (Northcote 1971).

These attributes i'lere considered to be of importance for the pur­

poses of this township development and should indicate to some extent

the en€:,:ineering requirements in given areas.

Table I (page 16) ShOV1S the broad classification and includes the

II factual Key" notation, an:}. the Unified ~olls Classification no~:ati()n.

';'::tblc II (pagu ~Q ) ind~_cat8s the d.istribution 0:' :>ciL:: g':-'OUT;,3 -t'L';;e'n

tIle land units encountered in the survey area.

Soil properties in relation to lc.nd capability

(i) Soil depth

Depth to solid rock is of importance \'lhen excavation must be

carried out. Pavement thickness and also foundation design

depend upon soil depth and soil type. hard rock close to the

soil surface poses problems \-lhere trenches must be excavated

to a specified gradient.

In the survey area, soils were classifiod as shallow when the

profile did not extend below 40 crn. Soils over 120 cm were

15~

classified as l:loderately deep, although this last category was

not well represented.

(ii) Texture and profile form

Texture and other profile characteristics which are directly re­

lated to soil pa,rticle size distribution have a considerable in­

fluence on the capability of a particular soil type.

Absorptivity, hydraulic conductance and the preGence or absence

of hardpans are important considerations influencing the

selection of filter fields for septic effluent treatment tanks.

Where soil profile permeability is very low, for example in the

broh'n or grey clays or in the solodic soils, hydraulic failure

and overtopping is a likely consequence. On the other hand, if

soil permeability at a given site is very high, effluent will

pass through the soil at an excessive rate and pollution of

ground wat(~r and streams is quite probable.

Areas of soil in land units 3b, 4a, 5a1, 6a, 7a are considered

suitable for septic filter fields with part of land units 5a2,

5b, 3a, 2e, 6ab marginally suitable.

(iii) Soil surface consistence

This has considerable bearing upon establishment and maintenance

16.

TABLE I SOILS CLASSIFICATION

Factual Key of Unified Soil Representative ClLssification

Profile

A. Skeletal soils (shallow stony soils) (K-) Uc1 .21 GM

B. 3hallow gravelly soils (Ks-) Uc1.22 GC & sp/GC

C. Sh.s.llow sandy soils Uc1.21 SP

D. Deep sandy soils

( i) Sil>~eous san:;s Uc1.22 ~'PI

(ii) Earthy sands Uc5.22 SM/SC (iii)Stratified sandy

SM( variable) alluvial soils Uc5.21

E. Gr.~rlational loamy alluvial soils

( i) red earths Gn2.12 SC ( ii) yellow earths Gn2 .. 82 SC

Fo TGxture contrast soils

(i) solodics Dy3.13 SC/CL (ii) soloths Dy3.11 SC/CL

G. Humic gleys 0/Gn2.81 OH/CL

H. C racking clay soils

( i) brown clays Ug5.34 CH hi) grey clays Ug5.16 CH

of vegetative cover. Vegetation is a major consideration in

the stabilization of soil within a township where trampling and

other soil surface disturbance is likely to be co::centrated.

vihere vegetative cover can be maintained and iiher<! run-off

patterns are adequately controlled, problems such as scouring,

gullying or wind blo"i\'TI dust will be minimized.

Soil performance with seasonal variation

Soil drainage within a profile shows good correlati<~ with soil

type. Thus, the heavy textured soils in land units 6b1, 6b2, 6ab, 6c,

6d i'Thich '(lave very 101:! permeabili ties and occur cn very 10vl gradients

aI":: very poorly drained follow"ing rain. The sandy soils in land units

3a, 3b, 4a, 5a1, 5a2, 5b, 6a, 7a, are very porous and have relatively

U.gh permeabili ties. They are generally , .. ell drained, at least in the

absence of widespread flooding.

Once the heavy clay soils in land unit 6b1, 6b2 and 6ab begin to

dry out, soil shrinkage, cracking and soil heave occur. This leads to

foundation instability and , .. ill result in structural damage to buildincs

and cracking of pavement and roads unless foundation design is modified

to compensate for this soil type.

Land forms along the river frontage should be expected to alter

following scouring and deposition associated with severe flooding.

TA}3LE II suljj\iArlY Ot' :.lOr.;, DISTRIllU'l'lCH B;';THE8111 Lf,ND UIHT3

L; L I-Ie -

SOILS 1a 1b 2a 2b 2c 2d 2e 3a 3b 4a 5a1 f.5a2 5b 5c 6a 6b1 6b2 6al 6c 6d 6e 6f 7a 7b 7c

A. Skeletal soils + + + + + + (+) (+) (+) - - r - .. - - - - - -,- - - - - - - -f-

! B. Shallow gravelly

I

soils + + + + + + + - + - - - - - - - - - - - - - - - - - -I

C. Shallow sandy soils + + - - + - + + + - + - - - - - - - - - - - - - - - -

D. Deep sandy soils

(i) Siliceous sands - - - - (+) - + + (+) + + - ( +) - + (+) - - - - - - - - - + -( ii) E'-lrthy sands - - - - - - (+) + + + (+) + + + + (+) + - - + - - - - + + (+ ) (iii) Stretified sandy

alluvial soils - - - - - (+) - - - - + (+) - + - (+) (+) - - - - - - ( +) ( + + (+)

E. Gradational loamy alluvial soils ( i) Red earths - - - - - - - - (+) - - - - - - - + - - (+) - - - (+) - - -(ii) Yellow earths - - - - - - :(+ ) - - - (+) - + + + (+) - - - - - - - - (+) - -

F. Texture contrast soils ~ . ) Solodics - - - - - - (+) - - - - - - (+) (+ ) + - - - - - - - - - - -~i) Soloths - - - - - - - - - - - - + - - - - - - -

G. HUIIlic gleys - - - - - - - - - - - + - - - ( -1-) - - - - - - - - - - -H. Cracking clay soils

1= (+) (i) Brown clays - - - - - - - - - - - - - - - - + + + - - + - - -

(ii) Grey clays - - - - - - - - - - - - - - - - + + + + + - - - - -

Kj~Y + dominant or co-dominant soil; (.i·) minor G(.:':d"reJ;ce of soil; - not represented.

Soil stabilization

(i) Clay soils

It is apparent that apart from flooding, a major problem in the

region of the township is the low trafficability of the heavy

clay soils especially after rain. These problem areas are de­

fined by land units 6b1, 6b2, 6c, 6d and parts o:.~ 6ab. This is

a function of gilgaied micro-relief, the plastic nature of the

material and the very high water holding capaci t~,r.

iVhere small areas of clay soils must be included t~; .inc ~ca'8 c:

proportion of useable land (for example in land unit 6ab) , the

addition of considerable amounts of sand or gravel from local

sources might provide a certain degree of stbbiljzation.

Roads and tracks should be l'lell formed, surfaced with porous

material, and numerous table drains should be provided to shed

water.

The clay soils are generally unsuited for building construction

si tes unless foundations can be protected from moisture C!lange.

Volume stability of the soil must be achieved to provent

structural damage to buildings on the cracking clay soils.

20.

(ii) Sandy soils

While 1and units 3a, 3b, 4a, 5a1 and 6a have general1y lower

hazards than most of the other areas, the poor structure and

low' cohe1"PTIce of the surface soil poses the problem of soil

erosion.

Stability may be improved by the ad1ition and mixing-in of

clayey soi 1 material to si t",s ,,!here disturbance is e1rj")9cted.

Cement stpbilisat.ion of path"JaYs in these land unj T.S is 8.1so 8.

possibili ty.

21.

5. V:;'::;GETATION

Intr.oduction

( . ) 1 I Communi ty structure of vegetation in the survey are? ranges

from grassland to low open forest. The classification is ba~pri

on that of S!)echt (1970).

(U) Trees, shrubs and grp..sses are Usted in the expanded. key in

orner of oomjnance for each lam'! 'mit.

ch_lorostachys and "E" is used for the g'P.nus Eucalyptus.

'T'he dist.rihl1tior. of various p}::mt grollps is i.nf'1llenced h3' P..

Y'1)'""::8eT' of edaphic f8CtOTS, such 8S soil depth, texture, "Inn w::,.ter hol,,-

hg capa.city, an" also hy ra.infall and topographi~ position.'·lth"1'er:

'"'(l"le species '3.re not restri~ted to specific loca.lities, th", J"'lPjority

e;row '"ithin a limited. r<mge of situatior.s. For eX8mo1e, Exc8.eCp.ri8.

parvi folia can tolerate sp.Hsonal flooding A.nd wi] 1. 170'" or. rea"y

i"px+'urpd sni 18 in poorly drained localj ties wheTp. most ,)ther trees

c::mnot survi.ve. If E. rnicrotheca occurs together vdth J<:::XcaecRria

.I:..:'3 rvi folia, 8liehtly hptter dred.nagp. 18 indicated. As 90i 1. orain?ce

22.

impr,oves, different plant groups emerge. An associatior of ]!. miniata

;:md E. tetrodonti:l, is indicative of well nrained soils. Thus it C3.!l be

S;:1id th8,t certain plants are diagnostir: and CB!l serve aE' indicators of

soil conditions.

Rxcaecaria "a.rvi folia, At'llaya hemiglauca, Acacia S~l. aff.

,!::}."wil 1 ii, ar.n E. microtheca occur on heavy clay nood p,ains wheT'P

veT'y poor drain2.ge exists. In oth,er almost as poorly dr:dned are?,"',

El. D8DU?Jla, Me13lpuc8. s+,r:mostachya, Terminali" canescens3,nd ri. nervosf.',

81'~e f:lund growinG.

enrths.

. , 'i,. polyc8.T1l2. ani F; •

'T: inia ta, ]!. tetrl)dc.mtR with scrub understory of which Buchanani'" 0bovata

is re~resentative.

Excessive n:rr-linage is frequently indica, ted by a dom~ nance o! annu8.~

f'l"'-'sses together "lith trees such as Call i.tris intratroni(a and

Petalostigma DubesceT's.

Grasses foum! on the treeless clay flood plains can be divided into

t-:iO groups. One group 1,rhich grows on the gilgai mounds consists of

Sehima nervos1L'TI, Heteropogon contortus, Iseilema sp., anc 'l'hemeda

.3.£~tralis. The other group, which grows in the gilgai depressions consists

of Dichanthium tenuiculum, Panicum decompositum, Ischaemum sp. and

Aristida sp.. Chrysopogon fallax vms also prevalent on the clay plains,

but shovlGd no definite preference for gilgai mounds or depressions.

In some areas it was the dominant grass.

In the upland areas adjacent to the clay plains Triodia sp.

appeared to favour sandy, shallovT, 1>Tell to excessively clrained soils.

It has also been observed groviing on what seemed to be almost bare

rock. Right throughout the area the introduced vIeed Hyptis suaveoll~n:3 I'T;.,.S

present and in some areas ,,,as so dense that it completely eliminated

TIl-'. tive grasses, particularly on river levees. Hyntis suaveolens a~pears

'1) thrive on di~,tu~'L,;d soil surfaces.

Commercial use of native plants

No i-/Oody plants found \vi thin the area surveyed could be considered

commercially useful. 'frees were generally small in size and of roor

quali ty. fllost of tLe native grass species would provide rough grazing

for stock although fevi of these would have sufficient nutritive value

to maintain weight gain throughout the year.

Effect of fire

Fire appears to be a common occurrence in the area and seems to

have had a da~aginG effect on at least some of the native vegetation.

Al thoueh small stands of Calli tris intratropica ,,,ere found scattered.

throughout the Nesa zone,many mature trees had been killed, apparently by

fire, and no signs of regeneration could be found.

It is possible that l'fi th increasing settlement, the incidence of fire

has increased and the distribution of certain plants is still readjusting

to the nelV' burning regime.

Soil erosion and stabilization by vegetation

Because of the djfference j.n elevation of the plains slrface and the

NcArtl:ur lhver, a topoGraphical situation exists I'lhich lends itself to

act·:·~·.· erosion. 'rlo.is occurs mainly on the river frontage and ~,lso furt he

a,my from the river. In the area surveyed, both natural and man-made

erosion occurs in many places, mostly in the form of severe gullies. All

of t!:': {';ullies eXD.rnined shmvnd evidence of rarj d ero~3i ,n with very Ii. t tIe

sign of natural stabilization. Host of the vegetation affected by

GUlly i.ng vias dead due to the rel110val of soil from around the plant roots.

There were some grasses established in eullies on clay soils although the

star)ilizing efficacy of these vms doubtful. r·lan-made erosion was found on

the access points to the river frontage and also around and within

aboriginal camps. The main causes i'lere considered to bo poor location and

inadequate construction of tracks for vehicular traffic and destruction of

vegetation by fires and trampling.

Episodic flooding results in considerable alterations to the river

frontage through scouring and siltation and this is generally beyond the

25.

capabilities of vegetative stabilization.

Due to the weakly coherent nature of soils in the Neza Zone, clearing

of the existing vegetation "\'lOuld be likely to considerably f. ccelerate soil

erosion. See 7able III, Appendix 1, (page 58 ) and Table IV, Appendix 2

(pace' 60) fo:!' areas of erosion ha!6ard.

Fh.r< 3IJ8cies iuentified in the survey area are listed in Appendix 4

(page 62).

26.

6. SCHEMATIC CROSS SECTIONS SHOWING SPATIAL RELATIONSHIPS

OF LAND UNITS.

FIGURE 4. Spatial relationship of land units of the Borroloola Basin.

~ Sandy soil

1TnTIJ Clay soils

.. Swampy soils (clayey)

FIGURE 5. Spatial relationships of land units of the Mesa zone.

2c

~ Sandy soil material

~ Cretaceous sediments

~ Proterozoic sediments

FIGURE 6. Spatial relationships of land units of the Coastal plains.

5c 56

Sandy soils

1llIDl Silty soils

6f

2.0...

27.

L:lND UHF' DESCRIPTIONS .........--

Land Unit

1a Landform Elevated stony plateaux, generally isolated; . slopes less than 2.5%; relief to 2 m.

Soils Outcropping rock pavement and skeletal soils.

Vegetation Low woodland; ~. miniata, E. tetrQdQUia, Acacia sp., Triodia sp ••

Limitations Skeletal soils; this land unit OCClers as areas isolated by rugged terrain with difficult access.

Sketch Land unit 1a.

'~--la

/----- .

':JA r ........

Land Unit

1b Land form Elevated stony cuestas; slopes greater than 205% u:~ to 8",,0; relief to 10 m.

Soils Outcropping rock and skeletal soils.

Vegetation L01'1 open woodland; &. terminalis, &. ferruginea, Buchan,aniiJ. QRovata, Calytrix sp., 4('ac~a dimidiata, Triodia sp., Eri&chne obtusa.

Limitations Skeletal soils; these areas are isolated by rugged terrain with difficult access.

Sketch Land unit 1b.

I~---' ----16.-- -----~I

I

1 "'t-~ -~~:~ ~ J5~S6;J.

Land Unit

2a Land form

Soils

Vegetation

Limitations

29.

Rugged high scarps; slopes over 40% to vertical; relief 5 m to 35 m.

Outcropping rock.

Bare to low open woodland to low wo)dland; ..m. tetrodonta, iJ.. miniata, I. ferru,~, E. terminali~, Triodia sp., Aristida S1 ••

Excessively rugged terrain.

Sketch Land uni t 2a.

30.

Land Unit

2b Landform

Soils

Vegetation

Limitations

Eroded hills including knobs, mesa:>, low scarps and stony rubble strewn scree slopes; slopes 15% to 401b; relief to 25 m but commonly about 10 m to 15 m.

Rock outcrop and rare skeletal soL.s.

Tall shrubland to woodland; ,m. min: ata, !. tetrodonta, Ironwood, Acacia sp., Triodia sp., Aristida sp ••

Rugged terrain.

Sketch Land unit 2b.

1 I~--- 2b. -?

I I r ~

.. -. : ~'~ ',.~ \.\) '.- \'-.'

B . ~ -'

~~S~

Lemd Unit.

2c Landform

:3oils

Vegetation

Li'ni tati')l1s

Sketch

31.

Stony upper slones c.nd eroded crests; slopes 57; to 15¥&; relief to 2C m usually convex.

Lithosols, skeletal soils, sCattered out()rop and small areas of siliceous s~nds.

Tall shrubland to low' ,'Toodland; I-'ielr:.leuca steno_stachya, ];,. 12.ruinosa, I rcn."-ood., ?et:...<.l_Q§.JJ.r"mc: Dubescens, Callitrir, intratro',ica. i::"ioti(b s"j:., Triod.ia sp., Chry:sopoe;ol1 falla;f.

Skeletal soils; steep slopes; (utcrop.

Land unt± 2c

<..- --- . -- --- !).C _, ______ ~I

I I

I

Land Unit

2d Land form

Soils

Vegetation

Limi ta tions

32.

Stony wash slopes which contain incised stream lines and stony water coarses; slopes 5% to 15%; relief to 20 m; generally concave.

Lithosols, skeletal soils with scattered outcrop.

Variable but generally "scrubby"; E:x:caecaria parvifolia, Terminalia canescens, Jetalostigma pubescens. Triodia sp ••

Drainage pathw"ays; skeletal soils; steep slopes; scattered outcrop.

Sketch Land unit 2d

~ d -------->

t Co~v-s e bed l a-acA

Our c..V'of.($~s~)

Land Unit

2e Landform

Soils

Vegetation

Limitations

33.

Lovler sandy wash slopes; slopes :Jfo to 8%; relief to 5 m.

Scattered outcrop and seepage areas; earthy sands common; minor solodics in depr~ssions.

Tall shrub land to low woodland; li. Kicrotheca, ~. polycarpa, Melaleuca nervosa, M. 3tenostachya. Pseudopogonatherum sp., Chrysopogon latifolius, Ectrosia sp., Ischaemum sp ••

Seasonal drainage problems; soil delth; erosion hazard.

Sketch Land unit 2e.

(~ ~ '/ ~-----

I -----> I

Land Unit

3a Landform

Soils

Vegetation

Limitations

34.

Elevated sand plains on structural plateaux; slopes 1.5% to 3%; relief to 10 m.

Siliceous and earthy sands over rock; scattered areas of skeletal soils and rare outcrop.

Low woodland to open forest; ~. tetrodonta, E. ferruginea,j. terminalis, Ironwood, Alphitonia sp., Acacia sp., Triodia sp., Aristida sp., Chrysopogon fallax.

Limi ted extent vIi til difficult access usually over rugged terrain; erodible.

Sketch Land uni t 3a.

~----~------------------------------r--\

~---3a.

!Q I -=- __ ~_~~" >..:... "~l:. __ "..:.:: ___ " .

CS~~ scr\\ l . 0hA0 ~ ~S \-cr-NL. /

,

~>~

Land Unit

3b Landform

'30ils

Vegetation

Limi ta tions

35.

Elevated structural plateaux with erE.velly soil cover; slopes 1. 5,:~ to 3~~; relief to 10m.

Gravelly red earths, I..wually she.llovI .... ri th scattered areas of skeletal soils and outcrop.

Lo\'i' VToodlandto open forest; species similar to 3a with more cor~on occurrence of Pet~~ostj@Qa pube~, and Hypti..§. suaveolens.

Similar to 3a; gravel stripped areas occu.!.' in this unit.

Sketch Land unit 3b.

r------.....------______ _

<::::-- _. -.- '3 b_ ----~

Land Unit

4a Landform

Soils

Vegetation

Limitations

Gently undulating sand plain with minor shalloi,/", meandering drainage lines; slopes to 2.5%; relief to 10 m.

Siliceous. sands and earthy sands, both deep~

Low woodland to open forest; ~. polycarpa, Ironwood, Pandanus sp., lie microtheca, Melaleuca vjridiflora. Sorghum plumosum, Chrysopogon latifolius, Q. fallax, Aristida sp ••

Erodible if disturbed.

Sketch Land unit 4a.

- -~C\ - .. ---------7

Land Unit

4b Landform

Soils

37.

Braided, sandy courses to main tributary streams wi th recent sandy levees; small areas of 1-rater worn stony bed load and scattered clayey su.::.les; short steep slopes on stream banks; relief to 4 m. .

Coarse alluvial soils; rare exposure of under­lying rock.

Vegetation low open forest; ll.. napuanj?" ],. microtheca, llelaleuca viridiflora, 11. stenostachya. Ph.l.::.':£]lJ t8S

sp., Sporobolus sp., A-ri stida sp., lly."tis ..§.1i::J[ELQ.:t9J1S.

Limitations Drainage lines; water disposal problems; h::'G:lly erodible; rugged in places.

Sketch Land unit 4b

------>

'---____________ ----------------1

Land Unit

4c Landform

Soils

Vegetation

Limitations

38.

Springs and seepage areas which occur at foot of escarpments.

Organic, stratified soils and humic gleys.

Closed canopy paperbark forest; l<lelaleuca sp., Pandanus sp., Imperata cylindrica, Fimbristylis sp .. Ferns and vines also present.

Water logged and occasionally inundated; erodible.

Sketch Land unit 4c

I I 1~~-4L

IQ

Land Unit

5a1 Landform

Soils

Vegetation

Limitations

39.

Nearly level sandy flood plain relics; slopes bE~low 1.5%; relief to 3 m.

Yellow earths, earthy sands, less common siliceous sands; all deep.

Low woodland to open forest; E. papuana, Ironwood, Terminalia volucris, Hakea arborescens, Acacia sp .• Eri~chne obtusa, Aristida latifolia, Chamaeraphis hordacea, Chrvsopogon la tifolius, Hyptis suave olens.

Erodible if disturbed; infrequently inundated.

Sketch Land unit 5a1.

--7 (sa'J.)

Land Unit

5a2 kmdform

Soils

VeGetation

:3'o.tch

40.

Gently undulating portions of the coastal plains division. Slightly 10l1er elevati)n than 5a1; slopes to 2.5%; relief to 4 m.

Yollm1 earths; oaTtby sands; nino.C' occurl'ence of solodic soils in depressions.

Tall sh!'ubland; L~l[3"l~llca steno~:.t"ch:r .. , 1.::.. v.iG)":Q'cl'.8c2., i. ferrudnea, Ie..:talostigma Dubes,2.~. ChUs_QL:.OFOn .lfclla.x, lL:!1Ltis '§"1J..a_y"eo:~E)_ns.

:;'~o(le!'c"tely 10\J frocluency flooo.ing; d.rai:-:ace >:,'c,~)l.e:"'3;

erodible.

Land. 1.L'1i t 5a2

I

~

/1

Land Unit

5b Landform

Soils

Vegetation

Linli tations

41.

Undulating slopes of terraces and swales within coastal plains subdivision. Slopes to 5%, relief to 5 m.

Earthy sands; solodics occur in some of the swales.

Low open woodland to open woodland; ~. polycarpa, Ironwood, la. papuana, Acacia sp.. Eragrostis sp., Eriachne sp., Setosa sp., Hyptis suaveolens.

Moderately low frequency flooding; highly erodible.

Sketch Land unit 5b.

~---5b. >

Land Unit

5c Landform

Soils

Vegetation

Limitations

42.

Broad swales and interconnecting fl(1odways with intermittent lagoons. Generally le\el-floored, marginal slopes to 1.5%; relief to cm. This unit indicates flood pathways.

Solodic soils and soloths; minor sardy wash along the fringes with 5a1 and 5a2.

Open scrub to low woodland; E. micrctheca, Melaleuca nervosa, 11. stenostachya. Sorghum .rlumosum, Chrysopogon 1atifolius, £. fallax, £eteropogon contortus.

Poorly drained soils; prone to flood Lng; erodible along margins of unit.

Sketch Land unit 5c.

1 -.~> (56)1

(Vi VI \ I

Land Unit

6a Landform

Soils

Vegetation

Limi tations

Almost level flood plain formed on fine gr&ined sandy alluvium. Slopes less than 1%; relief about 2 m.

Sandy red earths over red clays or bro~~ clays.

Low open vlOodland to open woodland; Irom'lOcd, 1:!,. cQnfertiflora, .§. terminalis, .m. microthec~., 1:!,. papuana. Sor€"hum plumosum, Heterooogon cortortus, ChrysQPo€"on fallax, Aristida sp., ]Iyptis suaveolens.

Low frequency inundation; erodible.

Sketch Land unit 6a.

-------7- (bf

5~ sa\l.

Land Unit

6b1 Landform

Soils

Vegetation

Limi tati ,ns

44.

Almost level flood plain with weakly developed gilgai. Slopes less than 1%; relief about 2 m. Gilgai amplitude less than .25 m, depressions up to several metres across.

Brown cracking clays.

Grassland; Dicanthium tenuiculum, Ischaemum sp., Iseilema sp., Chrysopogon fallax, Q.. latifolius, Aristida sp., Panicum decompositum.

Seasonal inundation; poorly drained; cracking clay soil; prone to moderate frequency flooding.

Sketch : Land unit 6b1.

->-~ (6~

9q ~~~~~~~~~~~~~~~~~~~~\ ,

~------------ ------------__ ...J

Land Unit

6b2 Landform

Soils

Vegetat:on

45.

Similar to 6b1 with more pronounced gilgai, amplitude to 1 m, depressions up to 6 m across.

Brown or grey cracking clays.

Low open woodland;; E,. microtheca, ,hcanthium tenuiculum, Panicum decompositum.

As for 6b1. Soil has greater swelling capacity.

Sketch Land unit 6b2.

~i

I ~d) ~----- b62 --

1E~nd Unit

6ab Lan form

GoLs

Vegetation

Lintations

Complex of cracking clay plain and san·:-:' !·lain. San~.1y ~~reas gnneraJ.ly slightly raised an irreg'ule.T sand sheets or as snaIl levees to old strean J.j.nes; these are essenti[:ll~; unmappable 6a aF).,.,.". over 6b1 or 6b2.

Combination of6a/6b1/6b2.

Grasslund and open woodJ.and. This '.,mit cOLlcdnes all t'-.e elements of 6a and Gb1.

PatchY fragmented distri.bution of soi18 :.Hh ~Jide=_:­differinG cl:eracteristics: i. e. \'lell clra:i :lee. sc.ndy soils and cracl.:ing cla:,'s. ;~efer to lirli.ta-:2-on:=; O~-.

6a ':'.l1d 6b1.

['''nd 1Jni"\; 6ab

(ba) ,

rv? f

/:/'1' ~~ Sd'\\,

\

' '~f~3.\

___ -----I

l:[.mc. Uni t

6c landform

Soils

47.

Broad shallo"l'T depressions on flood plairl; prononnced gilgai i·rith amplitude to 1 m, depressL)l1G to 4 m across. Slopes less than O. 75·/~, relief to 1.5 f1.

Brmm or gre~T crackinG clays.

0pGn scrub; E~Q.£<;:_G.A;:ia ..ll§.rvifoJ-ia, ., . ..£licrotllsc.k. Sesbapia sp., Dica.nthi1JJll tenuiculum, I scilemE'. S~I.,

Linitations Poorly drained; inundation; crackinf.' clay sOlL:.

Sketch Land unit 6c.

I ~----- be

Land Dni t

6d Le.ndform

Soils

OJ egetation

L:l.mitatior~s

48.

Br08.d sw"ampy areas ui thin the clay plains; almost level, relief to 1 m.

Inundated at time of sampling. ~:etj grey cracking clays occurred on the drier mE;.:r'gins of unit.

Low' open ~ioodland; ~. nicrotheca. F SCU:t9.1:E-'1.:..Q!}.;i.s spinescens, Dicantll.:h1dm: tenuiculum.

Long tern inundation.

Sketch Land unit 6d

.----·------T-

I

L Bread s~~.

----------------'

Land Unit

6e Landform

Soils

Vegeta tion

Limi ta tions

Eroding margins of the clay plain (6b1, 6b2) at heads of tributary streams. Slopes up to 15%; relief to 4 m; inter-gully ridges usually convex.

Red or brown cracking clays; profiles severely truncated.

Grassland; on ridges : Themeda sp., Sel).ima l\ervosum, ChrysoPQgoU fallax. In Bullies : DicanthiuPL t~nuicullllll' ~:tJ;mm sp., Ischaemum sp., Isei.lema sp ••

Unstable situation with excessive run-off occurrinp, over readily detached soil material; very erodib:le; rugged terrain.

Sketch Land unit 6e.

r-.- r be. -----7'

I

Land Unit

6f Landform

Soils

Vegetation

Limitations

50.

Active, severely eroded areas which occur where the sandy flood plain (6a) abuts on i o ~he river or its tributaries. Slopes to over 60;0; relief to 15 m; deeply incised gullies which appear to be actively cutting headwards. Some severely scalded more level areas occur within the unit.

Extensively truncated profiles of land unit 6a.

Grassland to low woodland; Excaecaria parvifolia, lie microtheca, Atalaya hemiglauca, !. polycarpa, lie ~apqana (dead trees common). Heteropogon contortus, ChrysopogQn latifolius, Aristida sp., Ischaemum sp ...

Severe erosion in an unstable, dynanic situation; rugged badland topography; excessivE run-off.

Sketch : Land unit 6f.

Land Unit

7a Landform

Soils

Vegetation

Limitations

51.

Broad crests of recent terraces and levees parallel to the river bank. Slopes to 3%; relief to 2 m.

Alluvial soils.

Open woodland; Ironwood, !. papUana, E. mic~otheca. Chrysopogon latifolius, Heteropo..,gQD. contort--IS, Hyptis suaveolens.

Moderate frequency of flooding; erodible.

Sketch Law!. unit 7a

I

"­

"

L_

Land Unit

7b LandfoIT.l

Soils . .

52.

Recent levee and svTale complex, parallel or sub-parallel to the river course. Slopes up to 8/,); relief to 7 m.

Alluvial soils and minor coarse bed load in depressions. Outcropping rock is occasionally exposed in the s~1ales.

Vegete.tion Open vlOodland; species composition similar to 7a.

Limitations Moderate frequency of flooding; highly erodible.

Sketch Land unit 1b

-76

Land Unit

7c Landform

Soils

Vegetation

Limitations

Sketch

53.

Active river frontage and major tributaries. Slopes to over 60%; relief to 1 m.

Alluvial soils, cornnonly tr~~cated.

River frontage vegetation; scattered Helaleuca Gp. and steep, bare areas.

Rugged topography; flooding; highl:' erodi blc: :Lr, a dynamic situation.

Land unit 1c

~lG

REFERENCES

Aerial photography (1966) McArthur River, RC8 8,200 feet altitude, 20

chains to the inch.

Aldrick, J.N. and Robinson, C. S. (1972). Report on the land units of

the Katherine-Douglas Area N.T. 1970. Land Conservation SerieG

No.1 Northern Territory Administration Darwin N.T ••

Bore Log data (1974) 'Ivater Resources Branch Dept. of N.T ••

Hug, K.N. (1974) Water Resources Branch Report.

Horthcote, K.H. (1971). A factual key for the recognition of Australian

soils. (Fourth edition) Aust. Div. of Soils Div. Report.

Publ. Rellim Tech. Public., Glenside, South Aust ••

Robinson, C.S. Ecology of the Hardman Basin N.T •• Technical Bulletin

No.6 Animal Industry and Agriculture Branch, N.T. Administration,

Darwin.

Scott, R.M. and Speight, J.G. (1966). McArthur River Land System Survey

C.S.I.R.O. Division of Land Use Research, Canberra. Technical

Memorandum 66/10.

Specht, R.L. The Australian Environment, 4th Edn. Edited by J.W. Leeper,

1970.

stace, H .C.T., Hubble, G.D., Brewer, R., Northcote, K.H., Sleeman, .J .R.,

Mulcahy, M.J., and Hallsworth, E.G. (1968) A Handbook of

Australian Soils. Publ. Rellim Tech. Public., Glenside, South

Aust. for C.S.I.R.O. and Int. Soc. of Soil Sci ••

TJ.S.D.A. (1960) Soil Survey Hanual. U.S. Dept. of Agric. (Soil Su,:,vey

Staff) U. S. Govt. Printing Office.

56.

APPENDIX I

SUITABILITY FOR URBAN DEVE10P~lENT (refer to Table III).

Definition of limitations to urban development

Inundation

Soil instabili ty

(iii) Flash flooding

Severe outcrop

Septic field problem

Rugged topography

Suitability ratings

area subjected to prolonged submersion;

soils are unstable because of either

swelling and heaving characteristics or

because of inherent erodibility;

area subjected to rapid rises and fall,-,

in water level;

areas with rock outcrop commonly present;

soils either too shallow or permeability

too high or too low; unfavourable terrain;

areas ,'Ti th rocky slopes in excess of about

10%.

Taking the above limitations into consideration, ratings have been established

for the land units. Where no limitations occur or where they are of minor

importance and can be allevir,ted with a minimum of effort, a land unit is

considered to be suitable for urban purposes.

57.

Symbols used in tables:

Limitations

Suitability

+ limitation present.

(+) limitation applies to only part of

unit or only occasionally.

limitation not present.

v area suitable.

(v0 suitable with some provisions.

X area not suitable.

58.

APPENDIX I. (Cant.)

TABLE I II - SUITABILITY OF LAND UNITS FOR URBAN DEVELOPMENT.

r LIMITATIONS OVERALL I

~-

Land 1 Soil F1 ash. Septic Rugg ,d SU I TAB I LI TY I

Unit i Inundation I nstabi 1 ity F1 oodi ng Severe Outcrop Field Problems Topogr Iphy , ,

1a I

- - - + ... - X

1b ... + (+) X I - - -I

2a I - - - + + + X

2b - - - + + + X

2c - - - + + + X

2d - - + + ... + X

2e - ... - (+) (+) (+) (I)

3a - - - - (+) - (j)

3b i - - - - - - '/ I

4a - - - - - - V

4b - ... + (+) ... + X

4e + ... (+) - ... - X

5a1 (+) - - - - - ../

5a2 + - + - (+) - X

5b + - ... - (+) - X

5e ... ... ... - + - X

5a (+) - - - - - (J)

5ab (+) (+) - - ( ... ) - (J)

6b1 + ... - - + - X

6b2 ... ... - - + - X

6e ... ... - - ... - X

6d + .... - - + - X

6e (+) + + - ... + X

6f ( ... ) ... ... - ... ... X

7a ... - + - - - X

7b + (+) ... - + - X

7e (+) ... ... - ... + X

59.

APPENDIX ,2

AGRICL1J,TURAL POTENTIAL (Refer toTable IV)

Irrigation is essential for successful horticulture in the area

because of the duration of the dry season (April to October). Unfortunately,

the level of salinity in the McArthur River, which is tidally influenced at

the tmmship, exceeds the tolerance of most crop species and renders water

from that source unsuitable for itrigation.

Small scale surface storage is not really considered as a practical

soluhon because of the generally poor command that possi ble sto~r·c~ ."', S1 tee

have over agronomically suited areas of soil. Conventional 1'Tater storage

would be aggravated by the high rate of evaporation in the region and by

exce::,~~ive run-off with associated siltation problems. Run-off harvesting

and ground"rater storage in the highly permeable soils of land unit 4a might

be one possiblo solution.

Areas "Thich are apparently most sui ted to horticultural practices are

defined by land units 4a, 5a1, 5a2 (part only), 6a, and 6ab (part only).

Land units 7a and 7b should also prove suitable although the incidence of

flooding is conSiderably higher.

Supplies of reasonably good quality groundwater occur :;n the vicinity

of the present townsite. (Reference Bore log data, Water Resources Branch

Dept. of N.T. 1974). Few problems, apart from urban compet~tion for land,

should be experienced there.

60.

APPENDIX 2 (Cont.)

TABLE IV - SUITABILITY OF LAND UNITS FOR AGRICULTURAl PRODUCTION.

LIMITATIONS SU I TAB III TY

Land Slope 1

Erosion Water- Flash Unit Risk Gravel OutcrJp 1 oggi ng Flooding Horticulture Extensive

I

1a - ! - (+) .... - X X -1b + - .... + - - X X

2a "" - (+) "" - - X X

2b + - "" + - - X X

2c "" .... .. + - - X .;

2d .... + .... .. - + X X

2e (+) .. - (+) + - X ../

3a - + (+) - - - X if

3b - + .... (+) - - X V I

! , 1

4a - i (+) - - - - ..; ,;

4b + .. (+) - (+) + X V

4c - - - - + (+) X X

5a1 + , - - - - - v v

5a2 - + - - - + (J) v

5b (+) + - - (+) + X v

5c - .. - - + + X v

6a - - - - - - v' V

6ab - - - - (+) - (v') J

6b1 - - - - + - X I 6b2 - - - - + - X ..;

6c - - - - + - X J

6d - - - - + - X X

6e + ... - - (+) + X X

6f + + - - - + X X

7a - .. - - - + .; ./ ,

V 7b (+) +. - - - + J

7c + + - - - .. X X

APPENDIX 3.

SLOPE CATEGORIES

Table V shows the maximum slope likely to be encountered lliLhin a land unit delineated on the map. It is in­

cluded as a guide to the relative steepness, or "r:!I~Gedne8s" o~ each land unit. In this report it is considered

that the engineering limitations to urban type development imposed by slopes greater_than 10'}'; rule out development

on steeper areas.

TABLE V :";1,Opg CATEGORI~S OF LAND -UNITS.

less than 2.5% If If

II If + - + I

- i- - !-

i +

II " 20;& + + ,

- I-I +

II " + I

-i 1- - - - -1- + - - +

- '--- ---'-- - _.- ._---------- '------ '----- '--_._----.

-1-!

________ ov_e~ ____ 4_0_'/o _______ ~_-,-_-_I,--+---, __ -_-,---_,---~,~_-_I. ~ ______ ~

62.

APl-'ENDIX 4.

PLANT SPECIES LIST.

Names of species found in the surveyed area, and common names

where appropriate :

Acacia aff. bidwillii ~ wattle Acacia dimidiata )

Alphitonia excelsa

Aristic!a bro'l'miana

vlire gras~;, feat;:,!, p

Atalaya hemiglauca whitewood

Bossiaea phylloclada

Brachychiton diversifolium kurrajong

Buchania obovata

Callitris intratropica cypress pine

Carissa lanceolata conkerberry

Chamaeraphis hordacea

Chrysopogon fallax golden beard grass

C. latifolius

Coelorhachis rottboellioides

Cymbopogon exaltatus scent grass

Dichanthium tenuiculum blue grass tassel

Dolichandrone filiiformis

Ectrosia sp. hare foot grass

Eragrostis sp. love grass

Eriachne obtusa

Erythrina sp.

Erythrophleum chlorostachys

Eucalyptus clavigera

E. confertiflora

E. ferruginea

E. microtheca

E. miniata

E. papuana

E. patellaris

~,

~. pol~fcarpa

1~ • 11·~·'J.ino,oa

E. setosa

E. t()r!:linalis

E. :"otrodonta

Excoecaria parvifolia

Gardenia megasperma

Grevillea pteridiifolia

Hakea arborescens

Heteropogon contortus

Imperata cylindrica

Ischaemum sp.

Iseilema sp.

Jncksonia sp.

wanderrie grass

coral tree, batwing tree

ironwood

cabbage gum

cabbage gum

coolibah

vlOolly bu tt

ghost gum

grey box

s .. ,amp blood .. lOOd

silver gum

stringybark

gutta percha

spear grass, bunch spear grass,

black spear grass

blady grass

cane grass

Flinders grass

Nelaleuca nervosa

M. sp.

H. stenostachya

M. viridiflora

Owenia vernicosa

Pandanus sp.

Panicum decompositum

~ ) ) )

~

Fetalostigma haplocladum

P. pubescens

Phragmites karka

Flechtrachne sp.

Fseudopogonatherum sp.

Pseud~r~phis splnescens

Schizachyrium sp.

Sehima nervosum

Seshania ~3p.

Sida sp.

Sorghum plumosum

Sorghum sp.

Terminalia canescens

T. volucris

Themeda australis

Triodia sp.

Vetiveria sp.

paperbark

emu apple

screw palm

pepper grass

quinine bush

reed tropical grass

spinifex

mud grass. water ':::";':ch

white grass

perennial sorghum

annual sorghum

kangaroo grass

spinifex

APPENDIX 5.

SOIL DESCRIPTIONS OF REPHESEt~TN1'IVE PROFILES.

Terminology used (Modified from the U.S.D.A. son 21JrveyManw-ll, 1960 and Northcote 1971).

Colour

Texture

Jv1unsell notation of moist soi1 sample (r1unsel1 soil colour charts, 1954).

Field hand texture of moistened sample, checked against mechanical analysis performed

on selected samples using International particle size standards.

Textures considered are -

1. S: sand, LS: loamy sand, CS: clayey sand (clay content up to 10%).

2. SL: sandy loam, fSL: fine sandy loam, ISCL: light sandy clay loam (clay content

up to 2(j}"f;).

3. L: loam, SiL: silty loam, seL: sandy clay loam (clay content up to 30%).

4. CL: clay loam, SiCL: silty clay loam, fSCL: fine sandy clay loam (clay content up

to 35%).

5. SC: sandy clay, SiC: silty clay, IC: Jieht clay, ImC: light medium clay (clay

40cf ) content up to Iv.

6. mC: medium clay, he: heavy clay (clay content over 45%).

(iii) Structure

Type Size

m massive co C' .. ';;'i'se ( 20 mm across) ang

bl blocky m medium (5 to 20 mm) s. ang

pr prismatic f fine ( 5 mm)

gr granular

(iv) Fabric

s sandy

e earthy

s g single grained

r p rough-ped

s p smooth-ped

(v) Consistence - resistance. of soil aggregates to crushing between thumb and fore finger.

d dry

m moist

w wet

1 loose

s soft

h hard

s

fr

soft

friable

fi firm

ns non-sticky s stic:ky

np n'n-plastic p } .. ~astic

v

sl

v

sl

very

slightly

very

slightly

Shape

angular

sub-angular

pH }l'ield pH i.s det()rmined on soU s8mples using: the Inoculo soil pH test kit.

Hepresentati ve profiles

Slopes greater than 10% were generally bare of soil.

A. Skeletal soils (shallm·r stony soils) Key: Uc1.21 (Worthro~~ 1971)

Developed on siliceous sedimentary rocks where the rate of erosion equals or exceeds soil formation.

Slopes are variable up to 10~6; drainage generally excessive. Outcrop, boulders and stone are common.

Depth Colour J:.lottles Texture Consistence Structure Fabric pH

A. 0-10 cm 10YR 4/3 - fLS ,,,iti: common dh i

m e 6 0 5 yellowish-brown rock fragments I

10 cm plus: hard sandstone~ I I I I i

B. Shallow gravelly soils Key: Ks-Uc1.22 (Northcote 1971)

These are also developed on siliceous sedimentary rocks where slopes are up to Zh. Gravel in profiles was most commonly ironstone nodules below a distinct sandy, leached A horizon. Several profiles were gravelly

throughout. Drainage rapid.

Dep,th Colour Nottles I Texture j Consistence Structure Febric pH :

I A. 0-10 cm 10YR 4/3 brown - S

I dl m e 6 0 5

I

B. 10- 50 i 10YR 5/6 I I 1 (1,,0 , yellowish-brown - S

I dl m I e .604 Fe

i I nodules I

6.4 50% G. 50-60 2.5YR 3/6 dark - grnv. E> I dlh m e Fe i

! nodules & red

J I j , Fe sandstone i - I

I I

h8.

C. Shalloh sandy soils Key: Uc1.21 (North~0te 1971)

These are simply deeper variants of the skeletal soils; 40 cm 1vas selected as the median depth of this

group. Again, the parent rock was siliceous sedimentary rock. Slopes were commonly below 3.%. Drainage is moderate to rapid.

I !

I Depth I Colour Nottles Texture Consistence Structure Febric pH t i ;

A. 0- 8 cm 10YR 3/3 dark - fSL dh m e 7.0 brown

B. 8-50 10YR 5/6 common flSCL dvh m e 6 0 5 yellowish-brown red-brown

t

c. 50 plus : weathering sandstone. I 1

D. Deep sandy soils

(i) Siliceous Sands Key Uc1.22 (Northcote 1971)

These generally occurred on sandy outwash from rugged sandstone areas. Drainage is usually very rapid

although in several cases, evidence for impeded drainage was noted by the presence of mottling in the B horizon.

Depth Colour Mottles Texture Consistence Structure Fabric pH

A1 0-10 cm 10YR 3/3 dark - S dl m e 6.5 I

brown ,

A3 10-25 7.5YR 4/4 dark S i dl s g 6.8 -I

m ~rown

B 25-120 7.5YR 5/4 brown - S I dl m s g 7 0 0 I

I

( ii) Earthy sands Key Uc5.22 (Nort1-Jcote 1971)

'rhese are similar to the siliceous sands with the exception or a better developed fabric and slightly

higher amount of clay in the profile. Drainage rapid.

I I I Depth Colour , Mottles i Texture Consistence Structure Fabric pH ! I

A1 10YR 4/3 brown ! I

I 0-10 cm - S dsh m e 6.,6

A3 10-60 10YR 5/6 yellowish-brown - S mfr m e 6.5

B 60-120 + 10YR 5/8 - S mfr m e 6.0 yellowish-brown

I

(iii) Stratified sandy alluvial soils Key Uc5.21 (Northcote 1971)

Th.ese are quite variable being formed almost entirely of recently deposited sandy alluvial and silty

material. Banding is quite o.bvious wi thin the profile and particle sizes range from silt through to

coarse gravels although size remains constant within a particular layer.

E •. Gradational lOamY alluvial soils

Red earths Key Gn2.12 (Northcote 1971)

,Depth Colour Mottles Texture Consistence jstructure Febric pH

A1 0-20 em 5YR 3/3 dark - LS dh 1

m e 6 0 5 reddish brown

A3 20-50 5YR 3/3 dark - fSL dh m e 6.0 reddish brown

B 50-100 2.5YR 3/4 dark - SCL dvh wk bl sp(wk) 6.,0 reddish brown

I D 100 + : Red m h clay. 6.8 I --

I

(ii) Yollo'.'1 earths Key Gn2.H2 (NoTthcote 1971 )

These vlere scattered throughout the survey area although no':; cur:lInon. 'l'hey appear to he associated

vli th some of the older alluvials although this is not certair,. Drainage is moderate to good.

Depth Colour i Mottles Texture I Consistence Structure Fabric I

! .A 0-10 cm 10YR 3/3 dark i - S1 dh m e

brown

B1 10-60 'lOYR 5/6 - SL dh m e yellowish brown I

B2 60-120 + 10YR '5/4 frint SC1 dh m e yellow'ish brown pa e yellow

I

pH

6 0 5

6.0

6.2

F. Texture contrast soils

Solodics Key Dy 3.13 (Northcote 1971)

These appeared to be associated with areas where seasonal waterlogging and infrequent silt deposition has

occurred. Soil drainage is imperfect to poor.

Depth Colour Mottles Texture Consistence Structure Fabric pH

A1 0-20 cm 10YR 3/2 dark common fSL dh m e 505 brown bellow

, rown

B 20-70 10YR 5/1 gray - mO with S mvfi wk bl sp 705

C 70-100 ..- 10YR 5/2 common mC ,vi til S mvfi m e 9.2 greyish brown pale ye 11 m-v

I

(ii) Soloths

The few soloths encountered were associated with finer textured sedimentary rocks with clay forming

minerals present. Slopes i'Tere up to 3}b \Vi tl1 these soils usu::llly on lower wash slopes. Drainage is

imperfect.

Depth Colour Mottles Texture I Consistence Structure Fabric pH I

A1 0-15 cm 10YR 3/3 dark - ~L dh m e 5.5 , br01'lIl

A3 15-35 10YR 5/6 common lSL dh m I e 5.5 yellowish brown faint

yellow brown

B 35-60 10YR 5/2 greyish common red 1 lC wi th S mfr m e 5.0 1 brown brown & yellow

B2 60-120 + 10YR 5/2 greyish common red ImC with S I mfi m e 50 0 i brown brown I , I

G. Humic gleys Key O/Gn2~81 (Northcote 1971)

'These were associated with the closed forest on perennial springs rising in places from the foot of the

sandstone escarpments. Decomposition of vegetative matter and exclusion of fire under the constantly moist

regir:le are the dominant forces determililing soil development. Organic horizons above the mineral soil layers and gleying within the B horizon from waterlogging are the main characteristics of these soils.

7') , .

H. Cracking clay soils

BrOiVll clays Key Ug5.34 (Northcote 1971)

These have developed on fine textured alluvium on the plains. Generally, soil reaction trends are neutral

to slightly acid, although in very few cases high pH waf-' encountered. Small quantities of sand were

invariably found in the profiles. Drainage if3 p')or. C r,,-cl-~i nc nearly ahIays present.

Depth Colour filottles rrexture i Consistence Structure Fabric pH -

I A11 7.5YR 5/4 lC S 0-10 cm brown - vii th I dvh m e 7.0

A12 10-100 + 10YR 4/4 dark faint mC I

with fs

I dvh wk bl sp 6 0 6

yellowish brown yellow bro"l'ffi ,

(ii) Grey clays Key Ug5.16 (Northcote 197 1 )

Genetically and texturally these are similar to the brown clays. They differ in chemistry and colour

"l'li th high pH or alkaline soil reaction trend being one of the more obvious differences.

·Basically, grey clays are more poorly drained than are bro"l'ffi clays. Again, strongly developed cracking

is a feature.

Depth Colour Mottles Texture Consistence Structure Fabric pH ,

A11 0-15 cm 2.5Y 3/2 vdk - IC with S dvh m ang bl vp f3 0 0 greyish brown

A12 20-110 +. 2.5Y 4/2 dark - mhC with mvfi co ang bl sp 8.5 greyish brown CaC0

3 nodules

I i