3. Formation of gravel bars

Agricultural University of Krakow, Departmentof Water EngineeringWojciech Bartnik, Leszek Książek, , Artur ARadecki-Pawlik,awlik, Andrzej StrużyńskiON SOME MOUNTAIN STREAMS AND RIVERSMORPHODYNAMICAL PARAMETERCHARACTERISTICS USING FIELD ANDNUMERICAL MODELINGCEM, Gdansk-SobieszewoMay 18-22, 2005

1. Introduction2. Mountain streams bedload incipient motionand bedload transport outlook3. Formation of gravel bars4. Modelling of fluvial processesForecasting of fluvial processes on the Skawa Riverwithin back-water reach of the Swinna Poreba waterreservoir5. Conclusions

1. IntroductionThe work present work concentrates on description ofsome basic parameters and features of the mountainousstreams which are responsible for morphodynamicalchanges in a their chosen cross sections.The paper deals firstly with description of theparameters of sediment motion in stream and the criticalconditions of motion – basically with the incipient of themotion of sediment,next is describing some features from themountainous gravel river bed which one can find in thefield andfinally the paper is showing a possibility ofmodeling the mentioned phenomena using the casestudy results from one of Polish mountain rivers.

2. Mountain streams bedload incipient motionand bedload transport outlookTenczyński Stream

2. Mountain streams bedload incipient motionand bedload transport outlookSkawa RiverFot. L. Książek., W. Bartnik

2. Mountain streams bedload incipient motionand bedload transport outlooknatural grainsmeasured d – from 1 to 12 cmzFot. A. Strużyński

2. Mountain streams bedload incipient motionand bedload transport outlookShape of grainsinfluences theintensity of bedformationprocesses

2. Mountain streams bedload incipient motionand bedload transport outlook- sorting and armoring- from heterogeneous touniform bed loadFot. A. Strużyński

2. Mountain streams bedload incipient motionand bedload transport outlookIn the flumethe electronicprofile-meterDISTANCE PROI is installed.Bed roughness is calculated as standarddeviation of data taken from measurementsof distance from bed.k shomogeneous roughness= K (1.926 SF2 – 0.488 SF +4.516)

3. Formation of gravel bars

3. Formation of gravel barsBank erosionFot. W Bartnik

3. Formation of gravel barsmid-channel barFot. A. Radecki-Pawlik

3. Formation of gravel barsalternate barsFot. A. Radecki-Pawlik

3. Formation of gravel barsbraided barFot. A. Radecki-Pawlik

3. Formation of gravel barsGravel bars reconaissanceAmount of deposited material

Few examples ofmeasurement methods forbedloadcharacteristics/transportation

Mountain streams bedload incipient motionand bedload transport outlookGranulometry sievingmethodFot. L. Książek

Mountain streams bedload incipient motionand bedload transport outlookp [%]10090807060504030201000 1 2 3 4 5 6 7 8 9 10 11 12 13 14d [cm]Granulmetry sievingmethodFot. L. Książek

Mountain streams bedload incipient motionand bedload transport outlookTraditional method of collecting probes of bed loadallow to describe only grains laying on the bedsurface. Probe is disturbanced. . Sample freezingmethod (using nitrogen) gives more benefits. Theprobe is taken as layer in bed. The sieve curves aremade for few separate layers (about 10cm thick)starting from bed surface up to 0.4-0.5 m deep. Thisgives possibility to describe bed change processeswhich can be expected in treated river.Sample freezing methodFot. A. Michalik

Mountain streams bedload incipient motionand bedload transport outlookp [%]1009080706050403020Warstwy:0-5 cm5-10 cm10-15 cm15-20 cm20-25 cm25-30 cm30-35 cm1000.00 0.02 0.04 0.06 0.08 0.10d [m]Measurement of bed material granulometry in layers

Mountain streams bedload incipient motionand bedload transport outlookRadioactive tracers(Cs 137 ) allowmonitoring of bedload initiation sheerstresses in naturalconditions.Thegrains are measured and drilled. . After this the radioactive tracer isinjected. Movement initiation of every categorized grain from the detector isnoticed.Fot. L. Książek

Mountain streams bedload incipient motionand bedload transport outlookThe flow conditions causinginitiation of every fractionmovement are exactly measured.After investigation all grains aretaken back from the river.Fot. A. Michalik

Mountain streams bedload incipient motionand bedload transport outlookQQmkkm3/ 2hIAds1/3Bg q2/3sMeyer-Peter, Müllerorginal formulaZurych 1934q hI f sd0,252/3isi1/ 3ipiMeyer-Peter, Müllermodified formulaFlow regime of mountain rivers differs fromlowland rivers so transportation of bedmaterial can be calculated by usingsimplyfied formula

Mountain streams bedload incipient motionand bedload transport outlookCritical stresses for multifractional bedmaterial

Mountain streams bedload incipient motionand bedload transport outlookSoftware written improve effectiveness of usedmethods

Mountain streams bedload incipient motionand bedload transport outlookq p 0 / cpdidmina( di)dmaxdminq(di)p0q(di)p0( di)( di)natural grainsmeasured d – from 1 to 12 cm

Mountain streams bedload incipient motionand bedload transport outlook 3.5 0.16 d m [m], c [kN/m 2 ]3d m0.142.50.1221.510.10.080.5 c0.0600 0.21 0.25 0.29 0.33 0.37 0.41 0.45 0.49 0.53 0.57water depth [m]0.04natural grainsmeasured d – from 1 to 12 cm

Mountain streams bedload incipient motionand bedload transport outlookst.dev9p. Tenczynski8765430 0,5 1 1,5 2 2,5depth[m]natural grainsmeasured d – from 1 to 12 cm

4. Modeling of fluvial processesMathematical model of the physical object, for example a reach ofthe river is a mathematical abstraction which combines: initialconditions, influence of the exterior parameters and the reactionfor that influence.Mathematical models are thesimplification of real objects.In real cases the model is acompromise between cost ofdesigning process of the model,collecting sufficient amount ofparameters which characterize theobject and accurance of results.Uselly the most important criterion isthe purpose of simulations.

FORECASTING OF FLUVIAL PROCESSES ON THESKAWA RIVER WITHIN BACK-WATER REACH OF THESWINNA POREBA WATER RESERVOIRThe aim of the project- to study sediment transport and related fluvial processes(armouring, agradation, erosion) within the backwater reachof the Swinna Poreba water reservoirWhich means: to better understand the impact of dams on theriver environment and river habitat and to develop numericalmethods that can predict their long term effects on the rivermorphology with regards to water reservoir operation and damsafety during the passage of floodsFot. L. Książek

The project is important for National WaterManagement and local communities because:1. There are several cities and villages within the back-waterreach of the Swinna Poreba water reservoir and we are obligedto provide safety passage of floods along that area2. It is important to predict the changes of fluvial processes inthe Skawa river before and after constriction of the SwinnaPoreba water reservoir. Those processes having place notonly in the Skawa catchment but also in all tributarieswatersheds to the Skawa (the Paleczka, the Tarnawka, theStryszawka streams)3. An instruction of exploitation of the water reservoir SwinnaPoreba could be prepared4. Prediction of places were erosion and depositions wouldtake place under back-water effect is important for river andriprarian habitats, deposition of some chemical components(eg. heavy metals) and invertebrates - whole river ecology

Main stages of the project ...Field measurementsComputer simulationsFot. L. Książek, M.Robakiewicz

Materials and methods- description of the research catchmentLocation of the Swinna Poreba water reservoirVISTULARIVERN10 kmCRACOWVISTULARIVERCRACOWTHE SKAWA RIVERSUCHABESKIDZKAFot. W. Bartnik

The Swinna Poreba water reservoir and theresearch reachthe damthe research area

Autumn2002Spring2004Autumn2004Fot. L. Książek

Materials and methods- field measurementsBackwater regionnear Zembrzycemeasurements:- distance 1800 [m] -31 cross-sections- 6 cross-sections formeasuring velocity(10 verticals each,3-5 points pervertical)- 12 freezing probesof bed load fromriverbed- 20 sieving probesof bed load fromriverbed- 50 roughness hightmeasurements- 300 grains werecollected for grainshape analysis

Field measurements

FieldmeasurementsGrain shapeGrain size class [cm]>8cm 6-8 4-6 2-4 0-2grain amount [%]Spheroid 0 0 0 0 19flatten ellipsoid 0 0 18 6 8lengthenedellipsoid0 33 22 7 4Disk 11 0 24 15 19Lengthenedboard33 34 12 30 26Cylinder 56 33 24 41 26Grain size distributionSF=0.381.6SFf 0.0123emCharacteristicdiameterNo 5flow current(bar 4 region)No 6left bank(bar 4 region)BridgeD 16[cm] 1.35 1.45 2.15D 50[cm] 6.45 4.20 6.70D 65[cm] 8.90 5.45 8.20D 85[cm] 11.70 8.50 12.90D 90[cm] 12.55 11.20 14.50p [%]10080604020Grain size distribution, cross-section II-II, probe 2Layers:0-10"10-2020-30"30-40"d m[cm] 4.98 6.55 9.29 2.94 2.42 2.4500 2 4 6 8 10 12 14 16diameter [cm]Fot. A. Michalik

Field measurementsThe Skawa River t-year floods23 July 200429 July 2004P[%] Q [m3/s]0.01 10050.10 7850.20 7160.50 6221.00 5482.00 4733.00 4274.00 3955.00 36910.00 28820.00 20525.00 17830.00 15740.00 12750.00 112Fot. L. Książek

Numerical modelingCCHE2D is a state-of-the-arttwo-dimensional, depthaveraged,unsteady,turbulent river flow,sediment transport, andwater quality evaluationmodel.

Mathematical model - GoverningEquationsThe model solves the momentum equationsFree surface elevation for the flow is calculated by thedepth-integrated continuity equation:Because many open channel flows are shallow waterproblems, the effect of vertical motion is usually ofinsignificant magnitude. The depth integrated 2Dequations are generally accepted for studying the openchannel hydraulics with resonable accuracy.The CCHE2D model uses the Efficient Element Method(special finite element method) to discretize the 2D depthaveraged shallow water flow equations.Continuity equation of bedload, bed changes - massbalance equation

Mathematical model - SedimentTransportSEDIMENT TRANSPORT MODELS to CCHE2DSelect Transport Capacity Formula0.01 - 0.15 mm - Laursen,0.15 - 2.0 mm - Yang,2.0 - 50.4 mm - MPM

The Skawa River andSwinna Porebareservoir -bathymetry file

The Skawa River – meshgenerating

The Skawa River – meshgenerating

The Skawa River – meshgenerating

The Skawa River – meshgenerating

RunsSkawaD1 280 m 3 /s 304,56SkawaD2 280 m 3 /s 306,5SkawaD3 280 m 3 /s 307,80SkawaD4 280 m 3 /s 309,6SkawaD5 205 m 3 /s 304,56SkawaD6 205 m 3 /s 306,5SkawaD7 205 m 3 /s 307,80SkawaD8 205 m 3 /s 309,6SkawaD9 112 m 3 /s 304,56SkawaD10 112 m 3 /s 306,5SkawaD11 112 m 3 /s 307,80SkawaD12 112 m 3 /s 309,6

Velocity magnitude for Q=35m3·s-1 alongthe back-water curve without back-watereffect

Velocity magnitude for Q=205 m3·s-1 alongthe back-water reach without back-watereffect

Velocity magnitude for Q=205 m3·s-1 alongthe back-water reach with back-watereffect

Velocity magnitude for Q=280m3·s-1 alongthe back-water reach with back-watereffect

Bed shear stress magnitude for Q=280m3·salong the back-water reach with back-watereffect·s -1

Simulated water surface levels (WSL) along theback-water reach without back-water effectLevel [m a.s.l.]316,00314,00312,00310,00308,00306,00The Skawa River, reservoir water surface level 304.56Bed levelDischarge Q=280 m3/sDischarge Q=360 m3/sDischarge Q=548 m3/sDischarge Q=785 m3/s304,00302,00300,000 200 400 600 800 1000 1200 1400 1600 1800 2000 2200Distance [m]

Average water slopes along the research section of theSkawa RiverDischargeQ [m 3·s -1 ]Calculatedslope of water surface[ - ]112 0,00360205 0,00383280 0,00385360 0,00387548 0,00390785 0,00410

Simulated water surface level for Q=35 m3·s-1 fordifferent water reservoir surface levelsCross-section XIV-XIV1.5km

Modeleded water surface levels (WSL(WSL) for differentdischarges with back-water effectCross-section XIV-XIV

Bedload transport rate along the back-water reachwithout back-water effectBedload transportvolume 1100 m 3

Bed elevationchanges: Q=205m 3 ∙s -1 with back-water effectBed elevationchanges: Q=280m 3 ∙s -1 with back-water effect

Measured and modeld d bed elevationwith back-water effect

Median size d 50 changes along the back-water reach without back-water effect

Initial and final mediansize d 50 changes alongwith back-water effect

Bed material composition for size class d>0.08mwith back-water effect

Grain size distributionat cross-section III-III fordischarge Q=205 m 3 s -1with back-water effect

Grain sizedistribution atcross-section XIV-XIV for dischargeQ=280 m 3 s -1 withback-water effect

Total bedloadtransport ratewithin selectedcross-sectionswithout backwatereffectTotal bedloadtransport ratewithin selectedcross-sections withback-water effect

Suspended load concentration for fraction 0.079 mm, m, dischargeQ=205 m 3 ∙s -1with and without back-water effectd i[mm] p i[-]0.001 0.080.010 0.120.034 0.30.040 0.20.048 0.20.079 0.1The initialcomposition ofsuspendedload material

Modeled suspended load concentration for fraction 0.079 mm, m,discharge Q=205 m3∙s-1 with and without back-water effect

Armored layer formation according to CCHE2D modeland ARMOUR for the same flow conditionsp i[%]100908070605040302010mixed granulometryarmored bedinitial2.53.52.75depth[meters]00 0.02 0.04 0.06 0.08 0.1 0.12 0.14d i [m]

4. Conclusions► The CCHE2D model allowed to predict in detailesmorphological changes along the reach of the Skawa Riverwhich is under influence of the back-water curve of theSwinna Poreba water reservoir,►►Back-water curve of the water reservoir Swinna Porebainfluences the initial conditions of bedload transport byreducing the value of shear stresses and because of thatstrong deposition takes place,The results of simulations the sediment transport quantityand armouring layer formation using the software developedat the Agricultural University of Krakow are comparable able withresults obtained fromnumerical modeling with CCHE2D,

ACKNOWLEDGEMENTThe project FORECASTING OF FLUVIAL PROCESSES ON THE SKAWA RIVER WITHINBACK-WATER REACH OF THE SWINNA POREBA WATER RESERVOIR is a result ofresearch sponsored by the US State Department Agency for InternationalDevelopment under Agreement No. EE-G-00-02-00015-00 and The University ofMississippi, which was technically supported by National Center for ComputationalHydroscience and Engineering (NCHE).

Fot. L. Książek