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ALLUVIAL BEDFORMS AND ROUGHTNESS

Transport Sedimentation Paper

Lecturer: Dr. Very Dermawan, ST.,MT

Munfarid (135 ! " 111 35 #$dam %i&una (135 ! " 1111 1" #'eta Li yananda Puspasari (135 ! " 1111 1! #)ana $rum 'ossy Tamaya (135 ! " 1111 1* #Marianty Pata+an& (135 ! " 1111 #Danan& -iswanto (135 ! " 1111 3! #'if i Mu/ammad 0 +a (135 ! " 1111 3* #$nnida Lisya/ada/ (135 ! " 1111 "* #'ia Puspasari (135 ! " 1111 5* #Mo/. $ i Ma+rur (135 ! " 1111 5 #02an Dwi Pra+owo (135 ! " 1111 !! #anisa 4 sina Sa amena (135 ! " 1111 !* #u2i6a 'e&a Siswanti (135 ! " 7111 7 #

Ministry of Education and Cu tur!

Bra"i#aya Uni$!rsity

Facu ty of En%in!!rin%

&at!r R!sourc!s En%in!!rin%

Ma an%' Indon!sia

()*+


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I, GENERAL

T/e +asic form sediments w/ic/ occur in a u2ia c/anne f ow rate re ated tot/e f ow re&ime. 8 ow re&ime, w/ic/ is a form t/at affects t/e f ow of t/eayer confi&uration. T/e fo owin& c assification s/ows t/e re ations/ip

+etween f ow 2e ocity and sediment transport modes (sediment transport#, t/econcentration of t/e transported sediment and forms t/e +asis of t/ere ations/ip +etween p/ase and water (surface water#.

8 ow re&ime can +e re ated to t/e 8roude num+er c/aracteri9es w/et/er f owwi +e ca m or fast. 8roude num+er is an e pression of t/e ratio +etween t/einertia (t/e force needed to stop t/e mo2in& partic es# and &ra2ity.

8 ;1 tran ui f ow ( ower f ow re&ime#8 < 1 critica f ow conditions (f ow re&ime transition#8= 1 rapid f ow (upper f ow re&ime#

0n &enera , t/e +asic s/ape of t/e f ow re&ime, sediment is c assified into:$. 'e&ime ow f ow>. 'e&ime transition f ow?. 'e&ime /i&/ f ow A, R!%i-! Lo" F o"


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(8roude num+er ; ." to 1 wit/ ramps transition#1. 8 at +ed, is a sediment transport wit/out deformation and t/e

mo2ement detai s are tossin& and turnin&. $nd t/e ma&nitude of t/es/ear of stress is e act y a+o2e from t/e critica .

. 'ipp es, t/e si9e is ; .! mm and t/e s/ear of stress is +ecome sma er t/an +efore. Sediments w/ic/ /as an re&u ar s/aped wa2es wit/wa2e en&t/s of 5@1 cm and a /ei&/t of 1 cm (+ase s/aped i6e are&u ar wa2e amp itude is re ati2e y sma compared wit/ t/ewa2e en&t/#.

3. Dunes, a si9es of sediment and t/e s/ear of stress increases to t/efront side. T/e front side is s ope s i&/t y, t/e +ac6 side is steeper.


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4rosion can occur on a sides of t/e upper reac/es, and depositionoccurs at t/e +ottom of t/e downstream side.

". Dunes, a si9es of sediment and t/e s/ear of stress increases to t/efront side. T/e front side is s ope s i&/t y, t/e +ac6 side is steeper.4rosion can occur on a sides of t/e upper reac/es, and depositionoccurs at t/e +ottom of t/e downstream side.

B, R!%i-! transition f ow(+asic confi&uration of t/e dunes towards t/e p ane +ed or anti@dunes#

C, R!%i-! /i&/ f ow(8roude Aum+er= ." to 1, a re ati2e y sma f ow resistance and ar&esedimentBs transport#


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1. P ane +ed, P ane +ed, /as a f ow rate &radua y risin&, sedimenttransport /as a f at /ei&/t. T/e mo2ement of t/e rain is ro in& or s idin& and c/an&es at a particu ar p ace. $ fine materia occurs sa tasi.

. $ntidunes, /as sediment materia s occurs in t/e upstream dunes,erosion on downstream. More or ess symmetrica wa2eforms.

$ntidunes mo2e downstream and occurs at 8r= 1

3. ?/ute and Poo s, occurs in t/e s ope, 2e ocity and sediment disc/ar&ew/ic/ are re ati2e y ar&e. T/e +asic form is a /i @ a ar&e sediment/i . T/e state of t/e f ow in c/ute is supercritica or su+critica .


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I, B!dfor- For!cast

Determinin& t/e criteria of +edform, approac/ used +y t/e sedimentcontinuity e uation as fo ows:

s C <

description:s < specific wei&/t of +ed materiay < /ei&/t of +edform at a on& t/e ri2ert < times < sediment f ow in a wei&/t unity wide and time

T/e first imitation s/owed a decrease in t/e rate of sediment at t/e +ase, andt/e second imit sediment transport s/ows t/e c/an&e in t/e c/an&e of t/edistance a on& t/e ri2er. 0t turns out t/at +ot/ t/ese imits &radua y a ways

opposite in si&n, w/en t/e +ase is formed positi2e and ne&ati2e.

.


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T/e ima&e a+o2e s/ows t/e cross@sectiona s/ape at time t and t C dt from t/e +edform t/at mo2es downstream. 0n t/e upper part of t/e ower forms of t/e

+asic situation w/ic/ is a function of time, so ne&ati2e.

8rom t/is e uation, seemin& y t/at positi2e, so t/at s increases

continuous y unti it reac/es its pea6.

4 ner (1 5#, assumed t/at:s < $o. uo

$o < constant

o < f ow 2e ocity near t/e +ase

>y enterin& $o and o into t/e sediment 4 ua ition continuity +efore, t/eno+tained :

s C $o <

0n 1 !3, -ennedy introduced t/e re ation +etween t/e wa2e en&t/ L of ac/an&e in t/e +edform of t/e 8roude num+er

'esu ts of -ennedyBs in2esti&ationed to t/e dominant wa2e en&t/ of t/e form@ t/e +edform is:

8r

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