RESEARCHES ON THE SIMULATION ON NUMERICAL MODEL OF THE ALLUVIAL TRANSPORT IN THE PERIOD 2005-2010 AND THE ESTIMATION OF THE MORPHOLOGICAL MODIFICATIONS, WITH APPLICATION ON THE DANUBE RIVER BED FOR A PROPOSED SECTOR

Victor Dumitrescu, Adrian Barbieru, Alexandru Carsmariu, IPTANA SA,. Romania

Abstract

The alluvial transport phenomena on a high water course is very complex, and its effects on the river bed mobility can be appreciated through qualitative and quantitative estimations with the help of using simulation through numerical type modelling on a characteristic period of time, considering the experience of some similar papers, and also based on time measurements of different hydro – morphological parameters in characteristic sections for the calibration and verification of the specific coefficients used by the used models.
-The elaborated researches regard the estimation of the Danube river bed morphological modifications, on an extended sector, situated upstream Bistreţ (km730) gauging station and downstream Bechet (km675) gauging station, with detailed application on a small sector (km 686+300-km 684+300) and punctual in a study section with sufficient data (km685+300).
 -The main objectives on the proposed researches achievement is constituted by the fields selection (hydrological, hydrometrical, geological, topometrical, software, etc) of the complex database necessary for the hydraulic type mathematical modelling and of simulation of the river bed specific phenomena simulation through aggradation or degradation:
- The modelling of the Danube river bed geometry on the limitary area (km 686+300 – km 686+300) through transverse profiles executed with small equidistance (around 100 m) for the flowing section between dams (Romanian bank) and slope (Bulgarian bank) and also on an extended upstream sector (km 730) and upstream (km 675) with bigger equidistance.
- The establishing of the granulometric composition of the sediment discharges (for each rate of water flow - 1000 m3/s)  and river bed for the potential eroded horizons taken from the geotechnical studies for the studied sector.
- The analysis of the chemical composition of the sediments from the river bed and the water chemistry of the Danube river with application on aggressiveness at metal and concrete (as auxiliary data).
- Hydrological data (daily average discharges, probability curves of the average and maximum water discharges) and the recent hydrometric activity at the above mentioned gauging station. The effective simulations on the model and the results elaboration were constituted on stages:
- An important chapter is represented the elaboration of the hydraulic calculations in the condition of model calibration (through the simulation of the flash – flood propagation waves recorded at Bistreţ and Bechet gauging stations) and of obtaining more precise results. The resulted and calibrated matrix data of the hydraulic model are used as primary entrance data for the simulation model of the alluvial transport and of the estimation of river bed morphological modifications for the Danube river analyzed sector.
- The choice of the mathematical model of alluvial transport type according to the calculation modules available. The choice of the specific functions (reported to the hydro – morphological data of the river bed) regarding: the simulation of the alluvial transport, establishing the sedimentary critical average speeds of training, and also the sorting of the alluvial particles from the river bed mobility gauge.
- The estimation of the morphological modifications elaborated on the Danube river bed through the simulation in impermanent regime of the daily average transited discharges recorded in the interval 2005 -2010 at Bechet hydrologic station.
- The calibration of the alluvial transport simulation model, the morphological evolution of the river bed on transverse measured profiles and calculations on the interval 2005 – 2010 at Bechet hydrological station
- Analytical and graphical results with application for the analyzed sectors: longitudinal general profile on the extended profile on the morphological evolution of the river bed; transverse profile for the punctual section with morphological modifications for significant periods of alluvial transport simulation
- Verification of the results for the punctual section (km685+300) and Bechet hydrological station (km678+660) on the apparition possibilities of degradation and aggradation phenomena of the river bed according to the used diagrams: average training speeds – water depth specific for the particles diameter d50.
- The analysis of the morphological modifications of Danube river on transverse profiles executed in the period 1980 – 2010 in the Bechet (km678+660) hydrological station with application on the obtained results on the model for the Danube river bed on the limitary sector
- Type SWOT analysis of the mathematical modelling regarding the estimation of the Danube river bed morphological modification phenomena and application extension possibilities.

Keywords: alluvial transport, morphologicial modifications, numerical  modeling