Agricultural University of Krakow, Department of Water Engineering Wojciech Bartnik, Leszek Książek, Artur Radecki-Pawlik, Andrzej Strużyński ON SOME MOUNTAIN STREAMS AND RIVERS MORPHODYNAMICAL PARAMETER CHARACTERISTICS USING FIELD AND NUMERICAL MODELING CEM, Gdansk-Sobieszewo May 18-22, 2005
1. Introduction 2. Mountain streams bedload incipient motion and bedload transport outlook 3. Formation of gravel bars 4. Modelling of fluvial processes Forecasting of fluvial processes on the Skawa River within back-water reach of the Swinna Poreba water reservoir 5. Conclusions
1. Introduction The work present work concentrates on description of some basic parameters and features of the mountainous streams which are responsible for morphodynamical changes in a their chosen cross sections. The paper deals firstly with description of the parameters of sediment motion in stream and the critical conditions of motion basically with the incipient of the motion of sediment, next is describing some features from the mountainous gravel river bed which one can find in the field and finally the paper is showing a possibility of modeling the mentioned phenomena using the case study results from one of Polish mountain rivers.
2. Mountain streams bedload incipient motion and bedload transport outlook Tenczyński Stream
2. Mountain streams bedload incipient motion and bedload transport outlook Skawa River Fot. L. Książek., W. Bartnik
2. Mountain streams bedload incipient motion and bedload transport outlook natural grains measured d from 1 to 12 cmz Fot. A. Strużyński
2. Mountain streams bedload incipient motion and bedload transport outlook Shape of grains influences the intensity of bed formation processes
2. Mountain streams bedload incipient motion and bedload transport outlook - sorting and armoring - from heterogeneous to uniform bed load Fot. A. Strużyński
2. Mountain streams bedload incipient motion and bedload transport outlook In the flume the electronic profile-meter DISTANCE PRO I is installed. Bed roughness is calculated as standard deviation of data taken from measurements of distance from bed. homogeneous roughness ks = K (1.926 SF2 0.488 SF + 4.516)
3. Formation of gravel bars
3. Formation of gravel bars Bank erosion Fot. W Bartnik
3. Formation of gravel bars mid-channel bar Fot. A. Radecki-Pawlik
3. Formation of gravel bars alternate bars Fot. A. Radecki-Pawlik
3. Formation of gravel bars braided bar Fot. A. Radecki-Pawlik
3. Formation of gravel bars Gravel bars reconaissance Amount of deposited material
Few examples of measurement methods for bedload characteristics/transportation
Mountain streams bedload incipient motion and bedload transport outlook Granulometry sieving method Fot. L. Książek
Mountain streams bedload incipient motion and bedload transport outlook p [% ] 100 90 80 70 60 50 40 30 20 10 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 d [cm] Granulmetry sieving method Fot. L. Książek
Mountain streams bedload incipient motion and bedload transport outlook Traditional method of collecting probes of bed load allow to describe only grains laying on the bed surface. Probe is disturbanced. Sample freezing method (using nitrogen) gives more benefits. The probe is taken as layer in bed. The sieve curves are made for few separate layers (about 10cm thick) starting from bed surface up to 0.4-0.5 m deep. This gives possibility to describe bed change processes which can be expected in treated river. Sample freezing method Fot. A. Michalik
p [%] Mountain streams bedload incipient motion and bedload transport outlook 100 90 80 Warstwy: 70 0-5 cm 5-10 cm 10-15 cm 15-20 cm 20-25 cm 25-30 cm 30-35 cm 60 50 40 30 20 10 0 0.00 0.02 0.04 0.06 0.08 0.10 d [m] Measurement of bed material granulometry in layers
Mountain streams bedload incipient motion and bedload transport outlook Radioactive tracers (Cs137) allow monitoring of bed load initiation sheer stresses in natural conditions. The grains are measured and drilled. After this the radioactive tracer is injected. Movement initiation of every categorized grain from the detector is noticed. Fot. L. Książek
Mountain streams bedload incipient motion and bedload transport outlook The flow conditions causing initiation of every fraction movement are exactly measured. After investigation all grains are taken back from the river. Fot. A. Michalik
Mountain streams bedload incipient motion and bedload transport outlook Qm k Q km q si 2/3 3/ 2 1/ 3 2 / 3 hi A s d B q s g h I f i s d i pi 1/ 3 0,25 Meyer-Peter, Müller orginal formula Zurych 1934 Meyer-Peter, Müller modified formula Flow regime of mountain rivers differs from lowland rivers so transportation of bed material can be calculated by using simplyfied formula
Mountain streams bedload incipient motion and bedload transport outlook Critical stresses for multifractional bed material
Mountain streams bedload incipient motion and bedload transport outlook Software written improve effectiveness of used methods
Mountain streams bedload incipient motion and bedload transport outlook q p 0 / c di q(di) p (di) 0 pa (di) dmin dmax q(di) p (di) 0 dmin natural grains measured d from 1 to 12 cm
Mountain streams bedload incipient motion and bedload transport outlook 3.5 0.16 dm [m], c [kn/m2] 3 0.14 dm 2.5 0.12 2 0.1 1.5 0.08 1 c 0.5 0.06 0 0.04 0 0.21 0.25 0.29 0.33 0.37 0.41 water depth [m] natural grains measured d from 1 to 12 cm 0.45 0.49 0.53 0.57
Mountain streams bedload incipient motion and bedload transport outlook p. Tenczynski st.dev 9 8 7 6 5 4 3 0 0,5 1 1,5 2 2,5 depth[m] natural grains measured d from 1 to 12 cm
4. Modeling of fluvial processes Mathematical model of the physical object, for example a reach of the river is a mathematical abstraction which combines: initial conditions, influence of the exterior parameters and the reaction for that influence. Mathematical models are the simplification of real objects. In real cases the model is a compromise between cost of designing process of the model, collecting sufficient amount of parameters which characterize the object and accurance of results. Uselly the most important criterion is the purpose of simulations.
FORECASTING OF FLUVIAL PROCESSES ON THE SKAWA RIVER WITHIN BACK-WATER REACH OF THE SWINNA POREBA WATER RESERVOIR The aim of the project - to study sediment transport and related fluvial processes (armouring, agradation, erosion) within the backwater reach of the Swinna Poreba water reservoir Which means: to better understand the impact of dams on the river environment and river habitat and to develop numerical methods that can predict their long term effects on the river morphology with regards to water reservoir operation and dam safety during the passage of floods Fot. L. Książek
The project is important for National Water Management and local communities because: 1. There are several cities and villages within the back-water reach of the Swinna Poreba water reservoir and we are obliged to provide safety passage of floods along that area 2. It is important to predict the changes of fluvial processes in the Skawa river before and after constriction of the Swinna Poreba water reservoir. Those processes having place not only in the Skawa catchment but also in all tributaries watersheds to the Skawa (the Paleczka, the Tarnawka, the Stryszawka streams) 3. An instruction of exploitation of the water reservoir Swinna Poreba could be prepared 4. Prediction of places were erosion and depositions would take place under back-water effect is important for river and riprarian habitats, deposition of some chemical components (eg. heavy metals) and invertebrates - whole river ecology
Main stages of the project... Field measurements Computer simulations Fot. L. Książek, M. Robakiewicz
Materials and methods - description of the research catchment Location of the Swinna Poreba water reservoir VISTULA RIVER N 10 km CRACOW CRACOW VISTULA RIVER THE SKAWA RIVER SUCHA BESKIDZKA Fot. W. Bartnik
The Swinna Poreba water reservoir and the research reach the dam the research area
Autumn 2002 Spring 2004 Autumn 2004 Fot. L. Książek
Materials and methods - field measurements Backwater region near Zembrzyce measurements: - distance 1800 [m] 31 cross-sections - 6 cross-sections for measuring velocity (10 verticals each, 3-5 points per vertical) - 12 freezing probes of bed load from riverbed - 20 sieving probes of bed load from riverbed - 50 roughness hight measurements - 300 grains were collected for grain shape analysis
Field measurements
Field measurements Grain size distribution SF=0.38 1.6 SF m f 0.0123e Grain size class [cm] Grain shape >8cm 6-8 4-6 2-4 0-2 grain amount [%] Characteristic diameter No 5 flow current (bar 4 region) No 6 left bank (bar 4 region) D16 [cm] 1.35 1.45 2.15 D50 [cm] 6.45 4.20 6.70 D65 [cm] 8.90 5.45 8.20 26 D85 [cm] 11.70 8.50 12.90 26 D90 [cm] 12.55 11.20 14.50 dm [cm] 4.98 6.55 9.29 2.94 2.42 2.45 Spheroid 0 0 0 0 19 flatten ellipsoid 0 0 18 6 8 lengthened ellipsoid 0 33 22 7 4 Disk 11 0 24 15 19 Lengthened board 33 34 12 30 Cylinder 56 33 24 41 Grain size distribution, cross-section II-II, probe 2 p [%] 100 Layers: 80 0-10" 60 10-20 40 20-30" 20 30-40" 0 0 2 4 6 8 10 12 diameter [cm] 14 16 Fot. A. Michalik Bridge
Field measurements The Skawa River t-year floods 23 July 2004 29 July 2004 P[%] 0.01 0.10 0.20 0.50 1.00 2.00 3.00 4.00 5.00 10.00 20.00 25.00 30.00 40.00 50.00 Q [m3/s] 1005 785 716 622 548 473 427 395 369 288 205 178 157 127 112 Fot. L. Książek
Numerical modeling CCHE2D is a state-of-the-art two-dimensional, depthaveraged, unsteady, turbulent river flow, sediment transport, and water quality evaluation model.
Mathematical model - Governing Equations The model solves the momentum equations Free surface elevation for the flow is calculated by the depth-integrated continuity equation: Because many open channel flows are shallow water problems, the effect of vertical motion is usually of insignificant magnitude. The depth integrated 2D equations are generally accepted for studying the open channel hydraulics with resonable accuracy. The CCHE2D model uses the Efficient Element Method (special finite element method) to discretize the 2D depth averaged shallow water flow equations. Continuity equation of bedload, bed changes - mass balance equation
Mathematical model - Sediment Transport SEDIMENT TRANSPORT MODELS to CCHE2D Select Transport Capacity Formula 0.01-0.15 mm 0.15-2.0 mm 2.0-50.4 mm - Laursen, - Yang, - MPM
The Skawa River and Swinna Poreba reservoir bathymetry file
The Skawa River mesh generating
The Skawa River mesh generating
The Skawa River mesh generating
The Skawa River mesh generating
Runs SkawaD1 280 m3/s 304,56 SkawaD2 280 m3/s 306,5 SkawaD3 280 m3/s 307,80 SkawaD4 280 m3/s 309,6 SkawaD5 205 m3/s 304,56 SkawaD6 205 m3/s 306,5 SkawaD7 205 m3/s 307,80 SkawaD8 205 m3/s 309,6 SkawaD9 112 m3/s 304,56 SkawaD10 112 m3/s 306,5 SkawaD11 112 m3/s 307,80 SkawaD12 112 m3/s 309,6
Velocity magnitude for Q=35 m3 s-1 along the back-water curve without back-water effect
Velocity magnitude for Q=205 m3 s-1 along the back-water reach without back-water effect
Velocity magnitude for Q=205 m3 s-1 along the back-water reach with back-water effect
Velocity magnitude for Q=280 m3 s-1 along the back-water reach with back-water effect
Bed shear stress magnitude for Q=280 m3 s-1 along the back-water reach with back-water effect
Simulated water surface levels (WSL) along the back-water reach without back-water effect The Skawa River, reservoir water surface level 304.56 316,00 Bed level Discharge Q=280 m3/s Discharge Q=360 m3/s Discharge Q=548 m3/s Discharge Q=785 m3/s 314,00 Level [m a.s.l.] 312,00 310,00 308,00 306,00 304,00 302,00 300,00 0 200 400 600 800 1000 1200 Distance [m] 1400 1600 1800 2000 2200
Average water slopes along the research section of the Skawa River Discharge Q [m3 s-1] 112 205 280 360 548 785 Calculated slope of water surface [- ] 0,00360 0,00383 0,00385 0,00387 0,00390 0,00410
Simulated water surface level for Q=35 m3 s-1 for different water reservoir surface levels Cross-section XIV-XIV 1.5 km
Modeled water surface levels (WSL) for different discharges with back-water effect Cross-section XIV-XIV
Bedload transport rate along the back-water reach without back-water effect Bedload transport volume 1100 m3
Bed elevation changes: Q=205 m3 s-1 with backwater effect Bed elevation changes: Q=280 m3 s-1 with backwater effect
Measured and modeld bed elevation with back-water effect
Median size d50 changes along the backwater reach without back-water effect
Initial and final median size d50 changes along with back-water effect
Bed material composition for size class d>0.08 m with back-water effect
Grain size distribution at cross-section III-III for discharge Q=205 m3s-1 with back-water effect
Grain size distribution at cross-section XIVXIV for discharge Q=280 m3s-1 with back-water effect
Total bedload transport rate within selected cross-sections without backwater effect Total bedload transport rate within selected cross-sections with back-water effect
Suspended load concentration for fraction 0.079 mm, discharge Q=205 m3 s-1 with and without back-water effect di [mm] pi [-] 0.001 0.08 0.010 0.12 0.034 0.3 0.040 0.2 0.048 0.2 0.079 0.1 The initial composition of suspended load material
Modeled suspended load concentration for fraction 0.079 mm, discharge Q=205 m3 s-1 with and without back-water effect
Armored layer formation according to CCHE2D model and ARMOUR for the same flow conditions pi 100 [%] 90 80 70 mixed granulometry 60 initial 2.5 50 3.5 40 2.75 30 depth [meters] armored bed 20 10 0 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 di [m]
4. Conclusions The CCHE2D model allowed to predict in detailes morphological changes along the reach of the Skawa River which is under influence of the back-water curve of the Swinna Poreba water reservoir, Back-water curve of the water reservoir Swinna Poreba influences the initial conditions of bedload transport by reducing the value of shear stresses and because of that strong deposition takes place, The results of simulations the sediment transport quantity and armouring layer formation using the software developed at the Agricultural University of Krakow are comparable with results obtained from numerical modeling with CCHE2D,
ACKNOWLEDGEMENT The project FORECASTING OF FLUVIAL PROCESSES ON THE SKAWA RIVER WITHIN BACK-WATER REACH OF THE SWINNA POREBA WATER RESERVOIR is a result of research sponsored by the US State Department Agency for International Development under Agreement No. EE-G-00-02-00015-00 and The University of Mississippi, which was technically supported by National Center for Computational Hydroscience and Engineering (NCHE).
Fot. L. Książek