<p>U radu su prikazani razvoj, testiranje, kalibracija i verifikacija linijskog modela neustaljenog tečenja vode i transporta nanosa u mreži prirodnih vodotoka.<br />Hidraulički model se zasniva na St. Venant -ovim jednačinama koje su diskretizovane primenom Preissmann-ove &scaron;eme. Za modelisanje transporta nanosa i deformacije korita je usvojen koncept koji daje mogućnost da se obuhvate oba vida<br />kretanja nanosa (suspendovanog i vučenog). Primenom pristupa aktivnog sloja su<br />definisani procesi razmene materijala između nanosa u suspenziji i nanosa u aktivnom sloju. Osnovne jednačine transporta nanosa i deformacije korita su rečene<br />primenom metode etapnog re&scaron;avanja čija primena rezultuje u dva uzastopna koraka, advektivnom i difuzionom koraku. Jednaˇcine advektivnog koraka su ređavane<br />metodom karakteristika, dok se za jednačine difuzionog koraka primenila CrankNicholson-ova &scaron;ema metode konaˇcnih razlika. Dobijene jednačine su dopunjene<br />sa dodatnim jednačinama kako bi se omogućilo modelisanje opisanih procesa u<br />granatoj mrezi otvorenih tokova. Izvedene jednacine su primenjene za formiranje<br />numerickog modela koji jeđvalitativno testiran na &scaron;ematskim primerima, a kvantitativni testovi su urađeni na realnom primeru. Za realan primer je izabrana deonica Dunava u Srbiji sa glavnim pritokama Savom i Tisom. Kako bi se definisala oblast koja će se koristiti za verifikaciju modela napravljen je detaljan pregled i sistematizacija postojećih merenja morfologije korita, nivoa, proticaja i koncentracija suspendovanog nanosa. Na osnovu ovog pregleda je definisana morfologija modelisane mreže tokova. Pri kalibraciji hidrauličkog modela su razmotrena dva pristupa,<br />kalibracija putem Manning-ovog koeficijenta zadatog kao funkcije od proticaja, i<br />kalibracija zadavanjem apsolutne hrapavosti, dok je verifikacija modela urađena<br />pu&scaron;tanjem simulacije od godinu dana i poređenjem rezultata proračuna sa merenjima. Kalibracija modela transporta je sprovedena za duži vremenski period kako bi se &scaron;to bolje opisale godi&scaron;nje varijacije koncentracije suspendovanog nanosa, a za verifikaciju modela je odabran petogodiˇsnji period tokom kojeg su upoređeni rezultati proracuna sa merenjima, čime je pokazano da razvijen model moze pouzdano da simulira procese strujanja vode i transprta nanosa u mreži otvorenih tokova.<br />&nbsp;</p> / <p>This work presents the development, evaluation, calibration and verification of a<br />one dimensional unsteady flow, sediment transport and bed evolution looped river<br />network model. The hydraulic model is based on the St. Venant&rsquo;s equations discretized using the Preissmann&rsquo;s scheme. The sediment transport and bed evolution<br />model implements a concept that differentiates sediment particles moving in the<br />form of suspended sediment, and near bed and bed sediment. Applying the active<br />layer concept the developed model includes definitions of the exchange mechanisms<br />between the suspended sediment and active layer material. The governing transport equations were solved using the split operator approach that resulted in two<br />successive steps, the advection and diffusion step. The advection step equations<br />were solved using the characteristics method, whereas the diffusion step equations<br />are discretized using the Crank-Nicholson&rsquo;s scheme. The obtained system of the<br />developed equations was complemented with additional equations in order to allow<br />sediment transport and bed evolution simulation in a looped river network. The<br />derived equations were applied to develop an open channel flow, sediment transport and bed evolution numerical model that was subjected to a series of schematic<br />tests and a real life situation simulation. The model&rsquo;s evaluation was conducted<br />by comparison of the simulation results with the available measurements. The presented work was complemented with an comprehensive overview of the existing<br />bathymetry, water level, discharge and suspended sediment concentration measurements in order to define the model&rsquo;s domain, initial and boundary conditions. The calibration of the hydraulic model was done by assigning the Manning&rsquo;s coefficient<br />as a function of the discharge. As a result of the exhausting requirements of this<br />approach, a second approach was considered, where the calibration is conducted by<br />changing the absolute roughness. The verification of the hydraulic model was done<br />by comparing the computed results of a one year flow simulation with the available<br />measurements. Since the agrement between the two was satisfying, the sediment<br />transport and bed evolution model was calibrated using a longer time interval in<br />order to better capture the annual variations of the suspended sediment. The calibrated model was employed for a long term sediment transport and bed evolution<br />simulation. The simulation results were compared with the existing measurements<br />confirming the developed model&rsquo;s reliability.</p>