Quantitative Application of Fluvial Geomorphology

8/9/2019 Quantitative Application of Fluvial Geomorphology

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Quantitative Application of Fluvial Geomorphology:

Preliminary Analogue Study from Modern Mahakam River,

Eat !orneo

Rian Cahya Rohmana1,2

Iqbal Fardiansyah2

Octavika Malda2

Agung Budiman2

!on"au#ani2 and $ovianto %risila&

• 1 Department of Geology UPN”Veteran”Yogyakarta,

• 2GeoPangea Research Group (GPRG,

• ! Remote "ens#ng $ Geomorphology %a&oratory' UPN”Veteran”Yogyakarta

"orreponding

author ' [email protected] ,[email protected]

Introduction

!orneo i kno#n a the larget iland in the Southeat Aia #hich drain through the longet and

$igget tropical river %appro&imately '(()*((( km in length and +()(( km #ide-. Mot of the riverare charged #ith great amount of edimentary material, reulting from e/uatorial #eathering

condition, and com$ination of climate, tectonic, $ae level change, and avulion %Schumm, *'01-.

2epite of high)reolution eimic image capa$ility that a$le to directly viuali3e paleogeography

appearance, /uantification of the fluvial morphology dimenion uing modern analogue #ill provide

further inight of channel tyle and depoitional facie geometry to the u$urface %Poamentier,

4((*-. 5hi article aim at $etter undertanding of fluvial control and morphology of Mahakam

River, !orneo uing 6andat data and field urvey %Figur! 1-. 5he morphometric meaurement aim

to predict paleo)channel hape, compoition of the ma7or lithologie, a #ell a variou parameterthat control their geometry.

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Figure *. Shuttle Radar 5opography Miion %SR5M- of !orneo 8land. Study area focue on

location highlighted $y coloured $o&e.

Mor(hom!tric M!asur!m!nt M!thod

Fluvial morphometric meaurement #ere performed from uptream to the do#ntream of the three

main river uing 6andat image. Meaurement include channel #idth %"9-, channel length %"6-,

meander $elt #idth %M!9-, meander #avelength %M6-, radiu of curvature %R"-, and inuoity

%S8- )Figur! 2*+ 5he variou tyle of fluvial morphology are related to $ed load or upended load

tranport and the cro ection of channel geometry that ho# the river #idth)depth ratio and the

inuoity %Schumm,*'01 #n Miall, 4((0 Gallo#ay, *'1*- )Figur! &*. Schumm; claification i not

necearily applica$le to e/uatorial river, hence it re/uire additional field meaurement in numerou

part of Mahakam River, uch a depth and ediment ditri$ution in order to contrain the data.



Figure 4. Morphometric meaurement method uing landat image %courtey of Google Earth, 4(*<-.

Meaurement conit of channel #idth %"9-, channel length %"6-, meander $elt #idth %M!9-,

meander #ave length %M6-, radiu of curvature %R"-, and inuoity %S8-.

Figure <."laification of fluvial tyle, follo#ing the fluvial)geomorphological claification of

Schumm %*'0<-, given in the left column %modified after Gallo#ay, *'1*-.

tatistic o# Riv!r Mor(hology, "y(!s, and Controls

5#o ma7or channel tyle are identified #ithin the =apua, Mahakam and !arito river: %*- high)

inuoity, and %4- lo#)inuoity channel. >igh)inuoity channel are characteri3ed $y the

development of meander croll $ar %ridge and #ale-, a$andoned channel ? o&$o# lake, and

lateral accretion. Schumm; claification %*'01- ugget that meandering channel relief ha a lo# tomoderate depth : #idth ratio, #ith muddy to mi&ed)ediment dominating the inide of the channel. 8n



addition, lo#)inuoity river can $e identified $y non)meandering croll $ar development #ith

vertical accretion, relatively traight channel and a moderate to high depth : #idth channel relief

ratio. 6o#)inuoity river are commonly filled $y coare ediment tranported a $ed load.

>o#ever, in ome area, $oth channel type are controlled $y Quatenary ediment, tructure, and

$edrock)incied morphology. 8n total, 4*< morphometric meaurement of the three river have $een

/uantified in order to predict the pro$a$ility of fluvial geometry. A tatitic e&ample of channel #idth

i ho#n in Figur! -.

Figure @. General tatitic chart ho#ing #idth meaurement of =apua,Mahakam,and !arito river.

a- cumulative pro$a$ility of channel #idth $- hitogram chart that reflect ditri$ution of channel

#idth, range from 4(( to @(( m, interpreted a meandering river ytem.

Mahakam Riv!r ).ast Born!o*

5he Mahakam River i the econd longet river in !orneo %appro&imately '1( km long-. 5he middle

to uptream part of the Mahakam River are located in the 6ong 8ram area, #herea the do#ntream

part i located in Sanga)Sanga. 9e recorded * meaurement along <4*.1 km of river. Geological

map and 6andat imagery ho# a high)inuoity river ytem developed in the up to middle Mahakam

River. 8n the do#ntream area, development of the river i predominantly controlled $y incied

tructure and $edrock of the Mahakam fold thrut $elt %Figur! / and 0-.



Figure +. "omparion $et#een 6andat imagery data %courtey of Google, 4(*<- and geological map

%GR2", *''<- of Mahakam River. ote that the river initially incied 5ertiary rock of Mahakam

Fold and 5hrut !el

Morphometric meaurement reveal that channel #idth %"9- of the Mahakam River range from

*@+ to *(<4 m %mean: <@( m, median: 41.<+ m, and mode: @04 m-, #ith meander $elt #idth %M!9-

ranging from 44 to <'< m %mean: *+4@ m, median: **0< m, mode: <0( m-, meander #avelength

%M6- range from *4*1 to **<' m %mean: @@0 m, median: <<(4 m, mode: ?A-, and radiu of

curvature %R"- range from '+ to 110 m %mean: @4* m, median: <11.+ m, and mode: <' m-.



Figure 0. A- Meander croll of Mahakam river lie in the uptream /uaternary ediment, the

a$andoned channel or o&$o# lake are clearly o$erved from landat image. !- 6ong traight channel

repreent tructural and $edrock incied river of Mahakam Fold 5hrut !elt.

Quantitative morphometric analyi e&poe imilaritie $et#een the Mahakam and =apua river.

"ro)plot channel #idth %"9- veru inuoity %S8- yield t#o main population trend. "la of data

dominated $y $edload and upended load tranport #hich ho# a linear relationhip, #ith

meandering ytem #idth range from B *(( m to C @((m %$ounded $y the red line on Figur! -.

8nvere relationhip indicate a lo#)inuoity to traight channel %S8 C *.@-, and the uncertainty of

channel #idth to more than *((( m %Figur! a-. "ro)plot of meander #avelength %M6- veru

channel length %"6- diplay three linear population trend. 8n $ed load tranport river, the potential

meander #avelength i follo#ed $y an increae of channel length. 8n contrat, the mi&ed and

upended load channel length are uually larger than the meander #avelength %Figur! b-. 5he

radiu of curvature %R"- veru inuoity %S8- relationhip infer that mi&ed and upended river

have large value ranging from up to *.@ to @ #ith the radiu of curvature over 4(( m to C '(( m

indicating a meandering ytem. 5he radiu of curvature may have #ide range to predict from

inuoity until #e are a$le to define the ma&imum and minimum $oundarie %Figur! c-. "luter of

homogenou $ed load tranport are poi$ly aociated #ith $edrock inciion and Dtructural; river

#ithout development of meander croll, #herea pare ditri$ution i interpreted a a meandering

river ytem %Figur! d*.





Figure 1. !athymetric urvey location in the Mahakam River, highlighted $y yello# $o&e

Figure '. a- !athymetric map of meandering river in the Muara Muntai %modified from >etina#ati,

4(('- $- ediment ditri$ution map ho#ing variou material inide the channel. 5hi indicate

mi&ed to upended load channel, an important clue that ugget channel thal#eg #a covered $y

mud plug and poi$ly turned to flo# $affle for and compartmentali3ation c- River cro)ection of

the channel coniting of ingle thal#eg #ith lo# to moderate #idth)depth ratio d- "ro)plot of

channel #idth %"9- veru depth %2- uggeting t#o population trend, and conclude that large or

#ide river tend to have large num$er of depth and depoited thick ediment.

>igh inuoity or meandering river ytem %S8 B *- are developed #ithin Quaternary ediment in the

uptream to middle area of the Mahakam River. 6o#)inuoity river %S8* to *.*- #ere initially

o$erved $y the preence of e&iting long and $ig river channel in the do#ntream area, a thechannel mot likely aociated #ith $edrock inciion and tructure. 5herefore, there i imilarity



$et#een the Mahakam and =apua river, $oth are controlled $y $edrock and tructure in the

do#ntream area.

A((lication to ubsur#ac! Int!r(r!tation

8dentification of channel tyle i important, particularly in reervoir analyi for hydrocar$one&ploration. 5he reaon $eing interpretation of river channel tyle hold fundamental control in the

geometry and heterogeneity of fluvial reervoir. Moreover, it can $e ued for further analyi on

reervoir characteri3ation in the development tage. 9idth and thickne of fluvial and $odie are

function of the hydraulic character of the river. 6ong)term, patial or temporal change in hydraulic

character are preerved a lateral or vertical change in and $odie %reervoir- dimenion. Short)term

hydraulic change in fluvial ytem are reflected $y intra)reervoir variation in grain i3e, haline

and edimentary tructure. 5hee lithological and te&tural variation e&ercie are eentially a$le to

determine ditri$ution of poroity and permea$ility in andtone reervoir %2avi et al., *''<-. Figur!

14 ho# the e&ample of morphometric identification uing high)reolution eimic time lice.

Figure *(. A- E&ample of <2 time lice %<<+ m- of mid)upper Miocene meander channel ytem in

the 9et atuna !ain %Fachmi and 9ood, 4((+-, ho#ing a meander cut off and croll $ar. !- 6o#)

inouity of $edrock incied channel ytem of Hpper Miocene, 9et atuna !ain %time lice, *@0

m- %Fachmi and 9ood, 4((+-. "- !edrock incied channel of Pleitocene E ava Sea, <2 time lice

'0 m %Poamentier, 4((*-.

8n area #ith pare data and?or <2 eimic time lice #ith lo# reolution, the morphometric

/uantification of 6andat image i ueful a an analogue to identify the paleo)fluvial tyle. Modern

geomorphic feature and morphometric parameter help to predict ancient fluvial morphology and it

dimenion, lateral facie aociation, dominant lithological content %haline, and ratio- and

varia$le control of geometry %faulting and local uplift-. Quantitative morphometric of modern fluvial

ytem i a critical component to develop kno#ledge in geologic interpretation, for e&ample

e/uence tratigraphy, reervoir heterogeneity and modelling, correlation trategie, drainage radiu,

and geo$odie, thu can minimi3e #ide range of uncertaintie.

R!#!r!nc!s



2avie, R. ., Poamentier >. 9., 9ood, 6. . I "art#right, . A. %ed- 4((. Seimic

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6ondon, Special Pu$lication, 4.

2avie, =.P., 9illiam, !. P. ., Jeell, =.P., *''<, 2imenion and Quality of Reervoir Kriginating

in 6o# and >igh Sinuoity "hannel Sytem, 6o#er "retaceou 5ravi Peak Formation, Eat 5e&a,

HSA, Geological Society, 6ondon, Special Pu$lication, v.<, p. '+)*4*.

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Petroleum Geology, Springer.

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Quantitative Application of Fluvial Geomorphology