This study investigates and compares several design storms for flood estimation in partially urbanized catchments. Six different design storms were considered: Euler II, alternating block method, ...average variability method, Huff’s curves, and uniform rainfall. Additionally, two extreme historical storms were included for comparison. A small, ungauged, partially urbanized catchment in Novigrad (Croatia) was chosen as a study area to account for the infiltration impact on the rainfall-runoff process. The performance of each design storm was assessed based on the flood modeling results, namely the water depth, water velocity, flow rate, and overall flood extent. Furthermore, several rainfall durations were considered to identify a critical scenario. The excess rainfall was computed using the Soil Conservation Service’s Curve Number method, and two-dimensional flooding simulations were performed by the HEC-RAS model. The results confirmed that the choice of the design storm and the rainfall duration has a significant impact on the flood modeling results. Overall, design storms constructed only from IDF curves overestimated flooding in comparison to historical events, whereas design storms derived from the analysis of observed temporal patterns matched or slightly underestimated the flooding results. Of the six considered design storms, the average variability method showed the closest agreement with historical storms.
Flood risk assessment at the mesoscale requires data that are spatially and thematically detailed enough to provide reliable estimates at the catchment level. However, data availability and ...suitability are often contradictory: available data are rarely suitable at the required level of detail. To overcome this problem, numerous disaggregation methods have been proposed in recent decades, often based on somewhat generalised imperviousness characteristics derived from the available urban land use/land cover (LULC) nomenclature. To reduce generalisation, we propose a new disaggregation approach using a spatially distributed imperviousness density (IMD) layer at a very detailed spatial resolution of 10 m as ancillary data to improve the thematic detail of the urban classes of the available LULC datasets (Coastal Zones, Natura 2000) and the dasymetric mapping of the census data. The nomenclature of the urban classes and the impervious density thresholds were taken from the detailed Urban Atlas dataset. The disaggregation of the census data is then built on the resulting geometry of thematically improved residential classes. Assuming that IMD values indicate a built-up density, the proposed weighting scheme is IMD-dependent: it accounts for variability in the built-up density and, hence, variability in population. The approach was tested in three catchments in Croatia, each with a different degree of urbanisation. The resulting statistics (mean square error and percentage error) indicate that residential areas and population density depend on IMD. Using IMD as additional data therefore greatly improves the assessment of elements that are exposed to flooding and, consequently, the damage and flood risk assessment.
In this paper, an assessment of the compound flood hazards in the city center of Rijeka due to the combined actions of the coastal and river flood sources was carried out, and hazard maps for the ...said area were prepared. Maps were created on a larger scale, taking into account various sources of flooding, and they show that the city of Rijeka has a high level of flood hazard, especially along the coastline and around the Rječina river where the highest flow velocities and water depths can be expected.
U ovome je radu provedena procjena opasnosti od složenih poplava u centru grada Rijeke uslijed kombiniranog djelovanja mora i rijeke te su izrađene karte opasnosti od složenih poplava za navedeno područje. Karte opasnosti od poplava izrađene su u krupnijem mjerilu uz uvažavanje različitih izvora poplava i potvrđuju kako riječko područje ima visoku razinu opasnosti od poplava, pogotovo uz samu obalu i oko korita rijeke Rječine gdje se mogu očekivati najveće brzine i dubine vode.
U ovome radu provedena je hidrološko-hidraulička analiza održivog sustava odvodnjeoborinskih voda na području grada Šibenika, odnosno komercijalne zone Dalmare.Cilj rada je procijeniti koliko ...plavo-zelena infrastruktura pozitivno utječe na sustavodvodnje oborinskih voda te na zaštitu okoliša. Rezultati provedenih analiza ukazujuna značajno smanjenje vršnog protoka i volumena otjecanja oborinske vode nakonizgradnje plavo-zelene infrastrukture, kao i na poboljšanje kakvoće oborinske vode.
A hydrological-hydraulic analysis of a sustainable storm water drainage system inthe city of Šibenik, the Dalmare commercial zone, was carried out in this study. Themain aim is to assess how the blue-green infrastructure (BGI) positively affects thestormwater drainage system and environment. The results of the analyses indicatea significant reduction in the peak flow and volume of stormwater runoff after theimplementation of BGI, as well as an improvement in the stormwater quality.
U ovome radu provedena je analiza sustava za odvodnju oborinskih voda s područja Sveučilišnog kampusa u Rijeci. Pored klasičnog razdjelnog sustava, predložen je i održivi sustav odvodnje oborinskih ...voda. Učinkovitost ovog prijedloga procijenjena je pomoću hidrološko-hidrauličkog modela. Rezultati su pokazali da implementacija održivog sustava odvodnje oborinskih voda može značajno smanjiti otjecanje do razine kakvo je postajalo na slivu prije početka izgradnje.
In this paper, an analysis of the stormwater drainage system at the University Campus in Rijeka is conducted. In addition to the classic stormwater drainage system, a sustainable stormwater drainage system has been proposed. The efficiency of this proposal was evaluated using a hydrological-hydraulic model. The results show that the implementation of a sustainable stormwater drainage system can significantly reduce runoff to pre-development levels.
This study presents a vulnerability assessment methodology that was developed to analyze the Croatian Eastern Adriatic Coast (CEAC), which has extremely complex geomorphology. Local coastal retreat, ...slope instability phenomena, and the influence of marine erosion play a significant role in coastal geohazards in the southeastern coastal area of the Krk Island (Kvarner area, northeastern channel part of the Adriatic Sea). Recent studies emphasize the need to develop an adequate methodology to monitor its evolution and define adequate risk management strategies. The vulnerability analysis was performed on the basis of the available data, taking into account local geological and oceanographic conditions. The coastal vulnerability analysis of the CEAC presents an adaptation of the existing methodology, emphasizing the significance of the geological factor, and providing novel elements of the parameter analysis (i.e., coastal slope, beach width, and significant wave height). This methodology was adapted and improved for the local rocky coast, but can be used on other complex rocky coasts worldwide. The calculated Coastal Vulnerability Index (CVI) around the Stara Baška settlement should be considered to have priority over the vulnerable areas in further monitoring and investigations.
•Roe scheme if very sensitive to the choice of eigenvalues.•IFCP and PVM schemes are less sensitive to the choice of eigenvalues.•Analytical eigenvalues are the best choice for Roe scheme ...overall.•Analytical eigenvalues are a better choice for PVM schemes for larger density differences.
The efficiency of several first-order numerical schemes for two-layer shallow water equations (SWE) are evaluated here by considering different eigenvalue solutions. This study is a continuation of our previous work (Krvavica et al., 2018) in which we have proposed an efficient implementation of a Roe solver for two-layer SWE based on analytical expressions for eigenvalues and eigenvectors. In this work, the accuracy and computational cost of numerical, analytical, and approximated eigenvalue solvers are compared when implemented in Roe, Intermediate Field CaPturing (IFCP) and Polynomial Viscosity Matrix (PVM) schemes. Several numerical tests are performed to examine the overall efficiency of numerical schemes with different eigenvalue solvers when computing two-layer shallow-water flows. The results confirm that analytical eigenvalue solutions are much faster than numerical solvers, with a computational cost closer to approximate expressions. Consequently, the Roe scheme with analytical solutions to the eigenstructure is equally efficient as the IFCP scheme. On the other hand, IFCP and PVM schemes with analytical solutions to eigenvalues are found to be equally efficient as those with approximated expressions. Analytical eigenvalues show slightly better results when dealing with larger density differences between the layers.
Procjena opsega poplave daljinskim istraživanjima Butković, Tea; Maretić, Andrea; Horvat, Bojana ...
Zbornik radova (Građevinski fakultet Sveučilišta u Rijeci),
12/2021, Letnik:
24, Številka:
1
Journal Article, Paper
Recenzirano
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U radu su, na primjeru poplave koja je u svibnju 2014. godine zadesila istočnu Hrvatsku, uspoređene tri metode kartiranja i procjene opsega poplavljenog područja: metoda analize refleksije s površine ...u blisko infracrvenom (IC) dijelu spektra (jednokanalna metoda) te metode vegetacijskog indeksa NDVI (Normalized Difference Vegetation Index) i vodenog indeksa NDWI (Normalized Difference Water Index). Metode kao ulazne podatke koriste snimke snimljene pasivnim senzorom ugrađenim na satelitsku platformu Landsat 8. Analizirane su četiri snimke; snimljene su prije (jedna snimka), tijekom (jedna snimka) i nakon poplave (dvije snimke). Procjena temeljena na jednokanalnoj metodi rezultirala je površinom manjom od površina procijenjenih primjenom višekanalnim metodama. Rezultati se mogu objasniti kompleksnošću spektralnog potpisa plitkih poplavnih voda s visokim udjelom suspendiranog nanosa koji će utjecati na refleksiju takvih površina u blisko IC dijelu spektra i klasificirati ih kao nevodene površine. S druge strane, kombiniranjem različitih spektralnih kanala u višekanalnim metodama kompenzira se utjecaj suspendiranog nanosa na refleksiju takvih voda te je klasifikacija na vodene i nevodene površine preciznija.
Using the example of flood in eastern Croatia in May 2014, the paper compares three flood mapping methods: reflection in near infrared (IR) interval of the electromagnetic spectrum (EMS) (one band method), and two multiband methods, namely Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index (NDWI). Input data for all three methods are satellite images recorded with the sensor carried by the Landsat 8 satellite. Four data sets were analysed: one recorded before the event, one during the flood and two images recorded after the event. Estimation based on the one band method resulted in the area smaller than the area estimated using the multiband methods. Such results may be explained with the complexity of the spectral signature of the shallow flood waters containing suspended load, which alters the near IR reflection from water surfaces and classifies them as non-water surfaces. Combining the various spectral bands in the multiband methods that impact is compensated and classification of water and non-water surfaces is more precise.
Monitoring and analysis of changes in the volume and area of nourished beaches is crucial to inform any beach renourishment programme. The aim of this study is to utilise UAV surveys and SfM ...photogrammetry to assess the beach nourishment performance of an artificial gravel beach exposed to a range of external forcing, including storms. The paper presents results from nineteen UAV surveys conducted between January 2020 and January 2021 at Ploče, an artificial beach in Rijeka (Croatia). The beach was nourished twice and eleven storm events, ranging from weak to strong, were recorded during this period. The Agisoft Metashape software was used to obtain point clouds and digital elevation models (DEMs) from UAV images; Matlab and CloudCompare were used for further analysis of the DEMs. The accuracy and precision of the DEMs was assessed and uncertainty levels of ±5 cm were applied to all derived DEMs. The study provides new insights into the response of the emerged part of the beach to storms. Predictably, the largest changes were recorded after the first storm following beach nourishment. The longshore variability in the beach response to storms was identified from full 3D point clouds. Most of the lost sediment was from the east side of the beach, while the rest of the beach aligned with the predominant wave direction through cross-shore and longshore processes. Offshore/onshore sediment exchange between the lower and upper beach face on the western side manifested itself in beach profile steepening and berm formations. Overall, changes in beach volume and area were small, indicating that this artificial beach is relatively stable. The embayed layout following the natural coastal configuration appears to be effective in retaining nourished sediment on the beach. This work highlights the need to consider pocket embayed beaches in three dimensions, as traditional transect studies can overlook the three-dimensional behaviour. This study also highlighted the wider potential of UAVs and SfM for studies of high-resolution elevation changes on natural and artificial beaches, as well as for coastal monitoring of beach nourishment.
Oborine su izrazito varijabilna komponenta bilance voda, koja ovisi o nizu faktora, kao što su geografski položaj, udaljenost od mora i nadmorska visina, a ključne su u razumijevanju hidroloških ...procesa nekog područja. Mjerenja oborina provode se na diskretnim lokacijama meteoroloških postaja (osim u slučaju radarskih opažanja oborina) te su saznanja o njihovoj varijabilnosti u prostoru rezultat primjene različitih metoda interpolacije izmjerenih vrijednosti u točki na analiziranom prostoru. U GIS okruženju, oborina može biti prikazana u formi diskretnog ili kontinuiranog polja pa će o tome ovisiti i odabir metode interpolacije. U radu su, na primjeru srednjih godišnjih količina oborina za razdoblje 1961. – 1990. na području Istre, prikazane i uspoređene tri najčešće primjenjivane metode prostorne interpolacije: Thiessenovi poligoni, TIN (Triangular Irregular Network) te VLR (metoda višestruke linearne regresije). Prve dvije metode ne uzimaju u obzir faktore koji utječu na količinu palih oborina, već su procijenjene vrijednosti u funkciji udaljenosti promatrane točke od oborinskih postaja. Za razliku od njih, metoda višestruke linearne regresije omogućuje određivanje vrijednosti oborina u prostoru u ovisnosti o drugim čimbenicima; u ovome slučaju to su geografski položaj, udaljenost od mora te nadmorska visina.
Rainfall is a highly variable water balance component that depends on numerous factors such as geographical location, distance from the sea, and elevation. Rainfall is crucial in understanding the hydrological processes in the given catchment. Rainfall measurements are performed at discrete locations at meteorological stations (except in the case of radar measurements). The knowledge of their spatial and temporal variability is the result of applying different methods of interpolation of measured values inside a given area. In a GIS environment, rainfall can be displayed in the form of a discrete or continuous field. Therefore, the choice of the interpolation method depends on the requirements for the type of the result. In this paper, three widely used methods of spatial interpolation are presented and compared to an example of estimating the average annual rainfall in Istria for the period 1961 – 1990. Namely, the following three interpolation methods are considered: Thiessen polygons, TIN (Triangular Irregular Network), and VLR (multiple linear regression method). The first two methods do not consider the factors that affect the amount of rainfall; they only estimate values as a function of the distance of the observed point from the rainfall gauges. In contrast, the method of multiple linear regression determines the spatial distribution of the rainfall from other factors, in this case, the geographical location, distance from the sea, and elevation.
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