For the purposes of planning and operation of maritime activities, information about wave height dynamics is of great importance. In the paper, real-time prediction of significant wave heights for ...the following 0.5–5.5h is provided, using information from 3 or more time points. In the first stage, predictions are made by varying the quantity of significant wave heights from previous time points and various ways of using data are discussed. Afterwards, in the best model, according to the criteria of practicality and accuracy, the influence of wind is taken into account. Predictions are made using two machine learning methods – artificial neural networks (ANN) and support vector machine (SVM). The models were built using the built-in functions of software Weka, developed by Waikato University, New Zealand.
Fragmentation of rivers has a negative impact on river’s ecological status which can be improved by the construction of fishways next to obstacles in rivers that prevent a free migration. Flow field ...characteristics are key factors in the design process of hydraulically efficient fishways—flow and turbulence patterns in a functional fishway allow fish to enter, progress through and exit with minimum time/energy expenditure. The aim of this paper is an experimental study of the flow field characteristics measured in the physical fishway model with the goal of providing information on the Reynold’s shear stress distribution that would facilitate their design in accordance with the environmental requirements. The focus of the research was on the nominally hydraulically efficient con-figuration pool-type fishways—pool-orifice and vertical slot. Fishway geometry was varied for bottom slope (7.5%, 10% and 12.5%), pool length (45 cm, 60 cm and 90 cm) and orifice size (8 × 8 cm, 10 × 10 cm and 12 × 12 cm) in a model scaled 1:3 to the prototype. Since Reynold’s shear stress has been identified as the main turbulent parameter affecting fish swimming performance and behavior, it is used as the basis for the analyses. The velocity data were collected with Vectrino ADV and processed in all three planes—streamwise, horizontal and vertical. Reynold’s shear stress data were analyzed according to the injury (>50 N/m2) and disorientation (>30 N/m2) biocriteria boundaries defined in the literature. The percentage of the flow field exceeding the boundaries were analyzed depending on the fishway geometry. The results obtained in this research suggest that the critical design parameter is the orifice size for the pool-orifice fishways and the pool length for the VS fishway. The Reynold’s shear stress is generally the highest in the bottom layer for pool-orifice fishways and the surface layer for vertical slot fishways.
Modeling of mean monthly flow is of particular importance for long-term planning of processes relying on water abstraction, such as reservoir operations. Advantage of data-driven models for these ...applications is the ability to predict monthly streamflow based on the combined hydrological and climatological input data. Methodology and recommendations for implementation of supervised learning (SL), from choice of input variables and optimization of model parameters in dependence of dataset size to final model evaluation, remains generally undefined. The main objective of this paper is to model mean monthly flow by SL models, while optimization algorithms (genetic algorithm-GA and simulated annealing-SA) are used to optimize and automate the choice of parameters and the reliable set of input variables. Detailed analysis of accuracy and amount of time needed to build three supervised learning models (ANN, SVM and NNM) for modeling of mean monthly flow is given in the paper. The 40-years input dataset has been shown as long enough for building models of satisfying quality, and was used in the further analysis where GA and SA were used first for optimization of model parameters, and later, for simultaneous optimization of both model parameters and input variables for SL models. In the analysis, time series was always split in building, calibration and verification part, while optimization was done on the building and calibration part. Data outside the particular time series was used for additional verification. Optimization of the model parameters by the exhaustive search indicated that the most accurate models were ANN and SVM, overperforming NNM across all data subsets, revealing that models need to be built with external variables. Optimization using GA and SA with SVM produced obvious movement toward optimal values, especially when the choice of parameters and input variables was optimized with GA-SVM.
Estimation of flood hazard associated with return period of a hydrologic event is the basis for design of flood protection structures. More frequent occurrence of flood events in recent history has ...imposed the need to reconsider traditional hydrological approaches to estimation of high flow events. This paper focuses on estimation of peak flood discharge at two confluences of the Sava River. The results show that the peak discharge trend estimated using bivariate copulas is comparable to the values measured during an extreme flood event in 2014.
Long-term planning of water engineering systems requires knowledge of long-term availability of water, most often in the form of monthly average flow information. Knowledge from stochastic hydrology ...is most often applied, although possible scenarios also involve generation of synthetic flow. The use of climatic models imposes the possibility of modelling based on future scenarios, and it is assumed in the paper that supervised learning can be applied for this purpose. The paper analyses accuracy of three supervised learning models in three approaches and the autoregressive model in the first approach, for predicting monthly average flow as related to the length of a historic dataset.
The Romberg extrapolation is applied on quadrature method solution of linear Volterra integral equations (VIE) of the second kind. An algorithm for new solution calculated by Romberg method is given. ...The calculated solutions show more efficiency and accuracy with less computation than solution with quadrature method over more points of integration.
This paper presents the results of numerical modelling of wave generation in the local waters of the channel and island system of the southern Adriatic Sea. The dynamics of gravity wind waves in the ...researched area is based on the results obtained from the prognostic atmospheric model Aladin. For verification of model results, results of measurements at a waverider station located in front of the town of Split were used. The model results and measurements covered the period from 1 November 2007 to 15 November 2008. The outcome of significant wave height fields is a statistical model with basic characteristics of a short wave climate, on the basis of which a long-term wave climate forecast has also been obtained, with a return period of five years. The resulting map of the wave height area may be applied in calculations of functionality of naval constructions.Original Abstract: U radu se prikazuju rezultati numerickog modeliranja valnog generiranja u akvatorijalnom podrucju kanalskog i otockog sustava juznog Jadrana. Dinamika gravitacijskih vjetrovnih valova na istrazivanom podrucju dobivena je temeljem rezultata prognostickog atmosferskog modela Aladin. Za verifikaciju modelskih rezultata koristeni su rezultati mjerenja na valografskoj postaji smjestenoj ispred grada Splita. Modelskim rezultatima i mjerenjem pokriven je period 1.11.07.-15.11.08. Rezultantna polja znacajnih valnih visina predstavljaju statisticki uzorak sa osnovnim obiljezjima kratkorocne valne klime temeljem koje je dobivena i dugorocna prognoza valne klime s povratnim periodom od 5 godina. Tako dobivena karta podrucja valnih visina moze se primijeniti u proracunima funkcionalnosti pomorskih gradevina.
Procjena opasnosti od poplava za hidrološki događaj zadanog povratnog razdoblja jest temelj projektiranja građevina namjenjenih sustavu obrane od poplava. Učestalo pojavljivanje velikih voda u ...kratkom razdoblju upozorava kako treba preispitati tradicionalne pristupe procjenjivanju vjerojatnosti njihovog pojavljivanja. U ovom radu procijenjena je opasnost od istovremene pojave velike vode na rijeci Savi i njezinom pritoku za dva ušća. Rezultati pokazuju da se trend protoka procijenjenih bivarijatnom kopulom poklapa s mjerenjima protoka velike vode 2014. godine.
Dugoročno planiranje hidrotehničkih sustava zahtijeva poznavanje dugoročne dostupnosti vode, najčešće u obliku srednjeg mjesečnog protoka. Uglavnom se koriste znanja iz stohastičke hidrologije, a ...mogući scenariji dobivaju se generiranjem sintetičkog protoka. Raspolaganje klimatskim modelima nameće mogućnost modeliranja iz budućih scenarija, a pretpostavka u radu je da se za tu svrhu može primjenjivati nadzirano učenje. U radu je analizirana preciznost tri modela nadziranog učenja u tri pristupa i autoregresivnog modela u prvom pristupu, za predviđanje srednjeg mjesečnog protoka, a u ovisnosti o duljini povijesnog niza.
Izgradnja bioloških staza (u inženjerskoj praksi uobičajeno ribljih staza) u određenoj mjeri umanjuje negativne ekološke utjecaje gospodarskog razvoja i omogućuje ostvarivanje uzdužne povezanosti ...vodotoka koja je ključna za zadovoljenje migracijskih potreba vodnih organizama. Tehničke riblje staze su od najčešće korištenih tipova ribljih staza za uzvodnu migraciju riba. Cilj ovog rada bio je izvesti nomograme za provedbu direktnog proračuna funkcionalnosti u postupku projektiranja tehničkih ribljih staza. S obzirom na riblje vrste na području RH u ovom radu su analizirana dva tipa: bazenske riblje staze i riblje staze s vertikalnim otvorima. Za funkcioniranje tehničkih ribljih staza najvažniji parametri su: dubina vode, kritična brzina tečenja u prolazima, osiguranje minimalnog protoka i volumetrijska disipacija snage u definiranim granicama. Za potrebe provedbe istraživanja izrađeni su fizički model u laboratoriju i numerički model u OpenFOAM-u. Na temelju provedenih istraživanja definirane su osnovne preporuke za projektiranje geometrije ribljih staza u hidrauličkim uvjetima određenim ribljim vrstama na području Republike Hrvatske.
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