NUMERICAL MODELLING OF THE MORPHODYNAMICS OF THE PLOČE GRAVEL BEACH IN RIJEKA

The morphodynamics of an artificial gravel beach in the Bay of Rijeka (Ploče Beach) was analyzed. The morphological changes of the beach face were monitored through an intense situation of gravitational surface wind waves from the incident SSW direction. A numerical modeling technique was applied, after initially establishing a numerical model for wave deformation. A model for sediment transport was established based on its results. Both models were based on the finite volume method. In addition, the partial contribution of the longshore component of sediment transport was analyzed based on empirical formulae. The modeling results were verified by comparing the positions and amounts of eroded/accumulated material along the beach with the processing of terrain images in the form of point clouds. The erosion and accumulation positions of the beach sediment material, obtained by numerical model simulations, corresponded to the surveyed positions. The total volume of eroded and accumulated material based on terrain image processing corresponded to the model values

FLASH FLOODS – CAUSES, MITIGATION MEASURES AND EXAMPLES IN CROATIA

Bujične poplave nastaju kao posljedica kratkotrajnih oborina velikog intenziteta ili uslijed puknuća/kvara hidrotehničkog objekta ili opreme. Karakterizira ih iznenadna lokalna poplava velikog volumena i kratkog trajanja koja nastaje u razdoblju od nekoliko, obično manje od šest, sati od jake kiše. Posljednjih godina, kao posljedica klimatskih ekstrema, bujične poplave su sve češća pojava pa i na područjima gdje se do sada nisu pojavljivale. Kroz upravljanje rizicima od poplava potrebno je dodatnu pažnju usmjeriti upravo na ovaj tip poplava jer su izuzetno opasne te mogu izazvati velike štete na imovinu i ljude. Kroz aktivnosti na lokalnoj razini bitno je educirati stanovništvo i osvijestiti na moguću opasnost od bujičnih poplava. Također potrebno poduzeti potrebne mjere kako bi se smanjili rizici od bujičnih poplava.Flash floods occur as a result of short-term, high-intensity precipitation or as a result of a failure of a hydrotechnical facility or equipment. They are characterized by a short duration and sudden local flood of large water volume that occurs within a period of several, usually less than six, hours from heavy rain. In recent years, as a result of climate extremes, flash floods are becoming more common, even in areas where they have not occurred before. It is necessary to focus extra attention on this type of floods, through flood risk management, because they are extremely dangerous and can cause damage to property and people. Through activities at the local level, it is important to educate the population and make them aware of the possible danger of flash floods. It is also necessary to take the necessary measures to reduce the risks of flash floods

Morphodynamik des Kiesstrandes Ploče bei starkem Schirokko

Provedena je analiza morfodinamike umjetno nasutog šljunčanog žala Ploče u Rijeci. Prvotno su provedene numeričke simulacije valnih deformacija i pronosa šljunčanog sedimenta za hipotetske situacije valovanja s incidentnim smjerovima SSE (157.50), S (1800), SSW (202.50) i SW (2250), te varijacijom značajnih valnih visina (HS = 1.0 m, 1.5 m i 2.0 m) i odgovarajućih vršnih valnih perioda. Parametrizacija numeričkog modela oslanja se na rezultate empirijskog obrasca za dužobalnu komponentu pronosa šljunčanog sedimenta i rezultate laboratorijskih istraživanja za poprečnu komponentu pronosa šljunčanog sedimenta. Nakon toga je provedena numerička simulacija morfodinamike za jednu situaciju jakog juga (6.3.2020.), s primjenom realnih uvjeta valova snimljenih na valografskoj postaji smještenoj u neposrednoj blizini žala Ploče i dinamikom morskih razina snimljenom na mareografskoj postaji Bakar. Verifikacija rezultata modelske simulacije za realno stanje okolišnih uvjeta provedena je kroz usporedbu pozicija i količina erodiranog/akumuliranog materijala uzduž lica žala sa obradom snimke terena u vidu oblaka točaka. Ukupni volumeni erodiranog i akumuliranog šljunčanog sedimenta temeljem obrade snimaka u suglasju su za sa modelskim vrijednostima.An analysis of the morphodynamics of the artificially filled gravel beach Ploče in Rijeka was conducted. The numerical simulations of wave deformations and gravel sediment transport were initially performed for hypothetical wave events with event directions SSE (157.50), S (1800), SSW (202.50) and SW (225°), a variation of significant wave heights (HS = 1.0 m, 1.5 m and 2.0 m) and corresponding peak wave periods. The parameterization of the numerical model is based on the results of the empirical pattern of the along-the-coast component of gravel sediment transport and the results of a laboratory investigation of the transverse component of gravel sediment transport. This was followed by a numerical simulation of the morphodynamics for one intense sirocco event (March 6, 2020), using the actual wave conditions recorded at the wave station located in immediate proximity of the beach Ploče and the sea level dynamics recorded at the mareographic station Bakar. The verification of the model simulation results for the actual environmental conditions was performed by comparing the positions and quantities of eroded / accumulated material along the shore with the terrain image processing in the form of point clouds. The total volumes of the eroded and accumulated gravel sediment based on image processing are in agreement with the model valuesEine Analyse der Morphodynamik des künstlich angelegten Kiesstrandes Ploče in Rijeka ist durchgeführt worden. Anfänglich wurden numerische Simulationen von Wellendeformationen und Feststofftransport eingesetzt für die hypothetischen Situationen von Wellen mit Inzidenzrichtungen SSE (157.50), S (1800), SSW (202.50) und SW (2250), mit der Variation von großen Wellenhöhen (HS = 1 m, 1,5 m und 2 m) und entsprechenden Spitzenwellenperioden. Die Parametrisierung des numerischen Modells beruht auf den Ergebnissen des empirischen Modells des Feststofftransports des Kieses entlang der Küste sowie auf den Ergebnissen von Laboruntersuchungen für die Breitenkomponente des Kiestransportes. Danach wurde die numerische Simulation der Morphodynamik einer Situation mit starkem Schirokko (am 6.3.2020) eingesetzt unter Anwendung von realen Wellenbedingungen, die auf der Wellenmessstation in der unmittelbarer Nähe des Strandes Ploče aufgenommen wurden sowie unter Anwendung der Dynamik der Meeresspiegel, die auf der mareographischen Station Bakar erfasst wurde. Die Simulationsergebnisse für die realen Umweltbedingungen wurden durch Vergleich von Positionen und Mengen an erodiertem/akkumuliertem Material entlang des Strandes mit der Bearbeitung der Geländeaufnahme in Form einer Punktwolke verifiziert. Die auf Grund von den Aufnahmen erfassten Gesamtvolumina von erodiertem und akkumuliertem Kies stehen im Einklang mit den Modellwerte

MORFODINAMIKA ŠLJUNČANOG ŽALA PLOČE U UVJETIMA JAKOG JUGA

An analysis of the morphodynamics of the artificially filled gravel beach Ploče in Rijeka was conducted. The numerical simulations of wave deformations and gravel sediment transport were initially performed for hypothetical wave events with event directions SSE (157.50), S (1800), SSW (202.50) and SW (225°), a variation of significant wave heights (HS = 1.0 m, 1.5 m and 2.0 m) and corresponding peak wave periods. The parameterization of the numerical model is based on the results of the empirical pattern of the along-the-coast component of gravel sediment transport and the results of a laboratory investigation of the transverse component of gravel sediment transport. This was followed by a numerical simulation of the morphodynamics for one intense sirocco event (March 6, 2020), using the actual wave conditions recorded at the wave station located in immediate proximity of the beach Ploče and the sea level dynamics recorded at the mareographic station Bakar. The verification of the model simulation results for the actual environmental conditions was performed by comparing the positions and quantities of eroded/accumulated material along the shore with the terrain image processing in the form of point clouds. The total volumes of the eroded and accumulated gravel sediment based on image processing are in agreement with the model values

Morphodynamik des Kiesstrandes Ploče bei starkem Schirokko

Provedena je analiza morfodinamike umjetno nasutog šljunčanog žala Ploče u Rijeci. Prvotno su provedene numeričke simulacije valnih deformacija i pronosa šljunčanog sedimenta za hipotetske situacije valovanja s incidentnim smjerovima SSE (157.50), S (1800), SSW (202.50) i SW (2250), te varijacijom značajnih valnih visina (HS = 1.0 m, 1.5 m i 2.0 m) i odgovarajućih vršnih valnih perioda. Parametrizacija numeričkog modela oslanja se na rezultate empirijskog obrasca za dužobalnu komponentu pronosa šljunčanog sedimenta i rezultate laboratorijskih istraživanja za poprečnu komponentu pronosa šljunčanog sedimenta. Nakon toga je provedena numerička simulacija morfodinamike za jednu situaciju jakog juga (6.3.2020.), s primjenom realnih uvjeta valova snimljenih na valografskoj postaji smještenoj u neposrednoj blizini žala Ploče i dinamikom morskih razina snimljenom na mareografskoj postaji Bakar. Verifikacija rezultata modelske simulacije za realno stanje okolišnih uvjeta provedena je kroz usporedbu pozicija i količina erodiranog/akumuliranog materijala uzduž lica žala sa obradom snimke terena u vidu oblaka točaka. Ukupni volumeni erodiranog i akumuliranog šljunčanog sedimenta temeljem obrade snimaka u suglasju su za sa modelskim vrijednostima.An analysis of the morphodynamics of the artificially filled gravel beach Ploče in Rijeka was conducted. The numerical simulations of wave deformations and gravel sediment transport were initially performed for hypothetical wave events with event directions SSE (157.50), S (1800), SSW (202.50) and SW (225°), a variation of significant wave heights (HS = 1.0 m, 1.5 m and 2.0 m) and corresponding peak wave periods. The parameterization of the numerical model is based on the results of the empirical pattern of the along-the-coast component of gravel sediment transport and the results of a laboratory investigation of the transverse component of gravel sediment transport. This was followed by a numerical simulation of the morphodynamics for one intense sirocco event (March 6, 2020), using the actual wave conditions recorded at the wave station located in immediate proximity of the beach Ploče and the sea level dynamics recorded at the mareographic station Bakar. The verification of the model simulation results for the actual environmental conditions was performed by comparing the positions and quantities of eroded / accumulated material along the shore with the terrain image processing in the form of point clouds. The total volumes of the eroded and accumulated gravel sediment based on image processing are in agreement with the model valuesEine Analyse der Morphodynamik des künstlich angelegten Kiesstrandes Ploče in Rijeka ist durchgeführt worden. Anfänglich wurden numerische Simulationen von Wellendeformationen und Feststofftransport eingesetzt für die hypothetischen Situationen von Wellen mit Inzidenzrichtungen SSE (157.50), S (1800), SSW (202.50) und SW (2250), mit der Variation von großen Wellenhöhen (HS = 1 m, 1,5 m und 2 m) und entsprechenden Spitzenwellenperioden. Die Parametrisierung des numerischen Modells beruht auf den Ergebnissen des empirischen Modells des Feststofftransports des Kieses entlang der Küste sowie auf den Ergebnissen von Laboruntersuchungen für die Breitenkomponente des Kiestransportes. Danach wurde die numerische Simulation der Morphodynamik einer Situation mit starkem Schirokko (am 6.3.2020) eingesetzt unter Anwendung von realen Wellenbedingungen, die auf der Wellenmessstation in der unmittelbarer Nähe des Strandes Ploče aufgenommen wurden sowie unter Anwendung der Dynamik der Meeresspiegel, die auf der mareographischen Station Bakar erfasst wurde. Die Simulationsergebnisse für die realen Umweltbedingungen wurden durch Vergleich von Positionen und Mengen an erodiertem/akkumuliertem Material entlang des Strandes mit der Bearbeitung der Geländeaufnahme in Form einer Punktwolke verifiziert. Die auf Grund von den Aufnahmen erfassten Gesamtvolumina von erodiertem und akkumuliertem Kies stehen im Einklang mit den Modellwerte