Comparison of models MIKE3 and PCFLOW3D: Hydrodynamic simulations in the Gulf of Trieste

Coastal sea circulation models are a useful tool for sea forecasting and a good starting point for calculating pollutant transport. Two similar three-dimensional baroclinic hydrodynamic models (PCFLOW3D and MIKE3) were compared on a case study of the Gulf of Trieste. The comparison was not based only on the graphic (visual) parameters, but was also numerically evaluated using the normalised root-mean-square deviation method (RMSDN). Typical cases of circulation were selected, where the similarities and differences between both models are clearly visible. Density-driven flows were studied, as well as the impact of strong wind (bora), mild wind (maestral) and the tide on circulation. In one case, constant coefficients of turbulent viscosity in the horizontal and vertical directions were used. In this case the results show dependence on the different numerical schemes and on the definition of boundary conditions of both models. In all other cases, the turbulence models used were as similar as possible, selected among the ones usually used in circulation models (Smagorinsky in the horizontal direction in both models and in the vertical direction k-є and Mellor-Yamada in MIKE3 and PCFLOW3D, respectively). An additional comparison with refined grid was performed in the events of density-driven flow and strong bora wind in the area of the Soča river inflow. The results of both models are similar. However, there are noticeable local discrepancies due to the differences between the models, mostly the different turbulence models and the boundary conditions definition. The results were also compared to simulations performed by the POM model. This three-way comparison showed in general a very similar picture of circulation. According to the results, both models, MIKE3 and PCFLOW3D, can be used interchangeably in areas with characteristics similar to the Gulf of Trieste

Neural network approach to sea-level modeling case study of a storm surge in the gulf of trieste in early december 2008

Tide tables can be a useful tool for sea-level forecasting in many areas. Slovenian operational\ud service for hydrological forecasts at the Environmental Agency of the Republic of Slovenia\ud frequently deploys tide tables alongside least square harmonic analysis to predict maximum sea\ud levels in the Gulf of Trieste. Meteorological influences such as pressure gradient, wind stress and\ud induced basin eigenoscillations (seiches) along the main axis of the Adriatic basin have repeatedly\ud been proven as important factors influencing the sea level in the Gulf of Trieste. They are, however,\ud only indirectly included in the harmonic analysis which in itself requires a large number of\ud carefully tuned model parameters in order to make useful short-range forecasts. A number of recent\ud reports show that an artificial neural network (ANN) can greatly improve sea level forecasts,\ud providing we supply it with suitable input variables (ie. previous water levels, air pressure, wind\ud speed, wind direction, tide charts etc.) We report on an ANN-based analysis of the recent storm\ud surge and flooding events at the Slovenian coast in the beginning of December 2008. The ANN\ud model compares favourably with the currently used conventional forecasting methods.\u

Comparison of trajectory and concentration methods in oil spill modelling at sea

Oil spills in the marine environment cannot be entirely prevented. In order to diminish their consequences numerous oil spreading and weathering models have been developed. The NAFTA3d model is based on the particle tracking method, its results are usually presented as oil concentrations at specified times. A new module based on the trajectory method showing the probability of oil slick occurrence at a certain location after a spill was added to the model. The article first describes both methods and functioning of the model. In the second part we present the results of performed simulations and analyse the suitability of the trajectory method by comparing concentrations and trajectories in the Gulf of Trieste and in the Northern Adriatic. In the third section we describe the strengths and weaknesses of the trajectory method. The study reveals that the new module is most suitable for oil spill response modelling, its major advantages being high computational speed as well as simple and efficient presentation of the entire area at risk on a single map. Finally, we propose a procedure for practical use of the trajectory method

Modelling of hydrodynamics and mecury transport in lake Velenje. Part 2, Modelling and model verification

PCFLOW3D - a three-dimensional mathematical model that was developed at the Chair of Fluid\ud Mechanics of the Faculty of Civil and Geodetic Engineering, University of Ljubljana, was used for\ud hydrodynamic and Hg transport simulations in Lake Velenje. The model is fully non-linear and\ud computes three velocity components, water elevation and pressure. Transport-dispersion equations\ud for salinity and heat (and/or any pollutant) are further used to compute the distributions of these\ud parameters. The results show that the major sources of mercury in Lake Velenje are lake inflows.\ud The hydrodynamic simulations revealed that ground and/or surface water inflow and outflow do not\ud have much influence on water cycling in the lake basin. Wind and ambient temperature seem to\ud have the greatest influence on water movement in the lake. Mercury transport simulations\ud performed by PCFLOW3D show good agreement with the measured distribution of different Hg\ud and MeHg forms in Lake Velenje. Verification of water flow was done by isotope tracers δ18O and\ud δ2H and measurements of different Hg and MeHg forms. Distribution of different Hg species and\ud forms and isotopic composition in water of Lake Velenje is described in Part 1

Riječni upliv na termohalina svojstva, zamućenost i suspendirane tvari u plitkom zaljevu (Koparski zaljev, sjeverni Jadran)

The influence of river discharge on the spatial and temporal variability of thermohaline and turbidity conditions at the sea surface (0.5 m) was studied in the shallow Bay of Koper (Gulf of Trieste, northern Adriatic Sea) which is influenced mainly by the polluted Rižana River. Conductivity, temperature and turbidity were measured monthly at 36 sampling sites between June 2011 and June 2013. Empirical orthogonal function analysis (EOF) was applied to investigate the data and to study the spatial distribution of variability and their temporal variations of temperature, salinity, density and turbidity. The EOF results showed an area of high variance in the proximity of the Rižana River mouth for all variables. The high variations in the time series for all variables were shown to be related mainly to high variations in the time series of the river discharges. Coupled field analysis showed the area of low salinity and high turbidity. A strong relationship was found between turbidity and suspended solid (TSS) concentration data collected in the local rivers and near shore zone suggesting that turbidity can be used as a satisfactory surrogate of TSS estimation.Utjecaj riječnog upliva na prostorne i vremenske varijabilnosti, termohalina svojstva i mutnoće na morskoj površini (0,5 m) je istraživano u plitkom Koparskom zaljevu (Tršćanski zaljev, sjeverni Jadran), koji je pod utjecajem uglavnom zagađene rijeke Rižana. Vodljivost, temperatura i mutnoća su mjereni mjesečno na 36 postaja između lipnja 2011. i lipnja 2013. Primijenjena je analiza empirijske ortogonalne funkcije (EOF) kako bi se istražili podaci i utvrdio prostorni raspored varijabilnosti, te vremenske promjene temperature, slanosti, gustoće i zamućenosti. Rezultati dobiveni EOF metodom su pokazali visoka odstupanja za sve varijable u području blizu ušća rijeke Rižana. Visoke varijacije u vremenskoj seriji za sve varijable su pokazala da se uglavnom odnose na visoke varijacije u vremenskom nizu riječnog dotoka. Združena analiza terenskih istraživanja pokazala je da se radi o području niske slanosti i visoke zamućenosti. Jaka veza je pronađena između zamućenosti i koncentracije suspendiranih krutih tvari (TSS), dok podaci prikupljeni u lokalnim rijekama i u neposrednoj blizini obale upućuju na to da se zamućenost može koristiti kao zadovoljavajući surogat za TSS procjene

Numerical simulation of debris flows triggered from the Strug rock fall source area, W Slovenia

The Strug landslide was triggered in December 2001 as a rockslide, followed by a rock fall. In 2002, about 20 debris flows were registered in the Kosec village; they were initiated in the Strug rock fall source area. They all flowed through the aligned Brusnik channel, which had been finished just before the first debris flow reached the village in April 2002. Debris flow events were rainfall-induced but also governed by the availability of rock fall debris in its zone of accumulation. After 2002 there was not enough material available for further debris flows to reach the village. Nevertheless, a decision was reached to use mathematical modeling to prepare a hazard map for the village for possible new debris flows. Using the hydrological data of the Brusnik watershed and the theological characteristics of the debris material, 5 different scenarios were defined with the debris flow volumes from 1000 m(3) to a maximum of 25 000 m(3). Two mathematical models were used, a one-dimensional model DEBRIF-1D, and a two-dimensional commercially available model FLO-2D. Due to the lack of other field data, data extracted from available professional films of debris flows in 2002 in the Kosec village were used for model calibration. The computational reach was put together from an 800-m long upstream reach and 380-m long regulated reach of the Brusnik channel through the village of Kosec. Both mathematical models have proved that the aligned Brusnik channel can convey debris flows of the volume up to 15 000 m(3). Under the most extreme scenario a debris flow with 25 000 m3 would locally spill over the existing levees along the regulated Brusnik channel. For this reason, additional river engineering measures have been proposed, such as the raising of the levees and the construction of a right-hand side sedimentation area for debris flows at the downstream end of the regulated reach

Siporek: a computer program for stimulating spills of hazardous chemicals in natural watercourses

Siporek is a computer program that was developed as a quick modelling tool for calculating the consequences of spills of hazardous chemicals in rivers. Basically, it is a 1-dimensional model, but it also enables us to take into account narrow accumulations (as it is the case in hydroelectric power plant constructions on rivers); it can be used in all cases where the flow is not explicitly 2- or 3-dimensional. The modelling results are in the form of a concentration curve along the channel and the speed of propagation of pollutants; for each calculation a c-t or a c-x graph is drawn. Additionally to advection and dispersion, the model takes into account evaporation and mechanical spreading of pollutants. Siporek can be used for modelling all types of rivers that can be found in Slovenia: from fast mountainous to slower flatland rivers. It is also possible to take into account a simplified representation of dams and waterfalls and their impact on river flow.\ud Siporek is a simple and user friendly program. It is written in C++, GUI is written in Qt 4.7. Computing time for one modelling case is about 1 second. Input data needed for computation are not many and not hard to acquire: simplified channel geometry data, channel slope, Manning's coefficient, discharge, data about pollutant spill dynamics. In general, a rectangular or a trapezoidal cross-section is used, while the axis of the watercourse is presented as a sum of linear segments with a uniform cross-section and constant parameter values. Moreover, to speed up the process of collecting the appropriate data in real cases, the chart of all Slovenian rivers broader than 5 m, on which all input parameters are shown, was prepared in advance.\u