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Analysis of uncertainties in the process of flood hazard maps elaboration : master thesis no.:98/II. VOI-FRM
ID Donevska, Jasna (Author), ID Rusjan, Simon (Mentor) More about this mentor... This link opens in a new window, ID Mikoš, Matjaž (Comentor)

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Abstract
Flood hazard mapping is an essential component of flood risk assessment, providing valuable information for preventive pre-impact hazard reduction, largely employed in spatial planning, risk management, and raising public awareness about flood hazards. Spatial and temporal variation of the natural processes, limited knowledge about the system's physical properties, and insufficient data introduce uncertainties in the modelling chain used to produce flood inundation and hazard maps, hampering flood risk management. This master’s thesis investigates the impact of uncertainties in hydrological and hydraulic parameterization and the related sensitivity of hydrological and hydraulic calculations and modelling on flood hazard mapping. Specifically, uncertainties related to the flow hydrograph shape and peak discharge value and variations in the channel and floodplain Manning's roughness coefficients were propagated through a combined 1D/2D hydraulic model using LiDAR Digital Terrain Model (DTM) combined with geodesy data of the Vipava river channel and detailed land use data. The uncertainty analysis was applied to the case study of the Vipava river, a transboundary river catchment shared between Slovenia and Italy, by comparing the flood extension and spatial distribution of flood hazard classes by performing hydraulic simulations associated with 10-, 100-, and 500-year return periods as specified in the Slovenian legislation. The analysis points out the greatest sensitivity of the results associated with variations in the channel Manning’s coefficients for a 10-year return period event, depicting an increase in the flood extent of 45%. The increase in the inundated areas is smaller for 100- and 500-year floods, amounting to 15% and 11%, respectively. Furthermore, the modelling results confirm the higher impact of the uncertainty in the peak discharge with respect to the impact of varying floodplain Manning’s values, denoting an increase in the flood extension of 9-12% between the 10% and 90% confidence interval values for the different flood occurrence probabilities. The maximum increase in the flood-prone area with the floodplain Manning’s coefficients amounts to 4-6%. Lastly, the impact of the flow hydrograph shape variations appears to be the lowest, depicting a maximum variation in the flood inundation area of 2-3%. All these changes in the overall flood extent are further reflected in variations of flood hazard classes, which are not uniform and not equally distributed for all but depend on the water depth distribution which is considered the dominant criterion for flood hazard classification.

Language:English
Keywords:civil engineering, master thesis, flood hazard mapping, flow hydrograph, hydraulic modelling, Manningʼs roughness coefficient, sensitivity analysis, uncertainty analysis, Vipava river
Work type:Master's thesis/paper
Typology:2.09 - Master's Thesis
Organization:FGG - Faculty of Civil and Geodetic Engineering
Place of publishing:Ljubljana
Publisher:[J. Donevska]
Year:2022
Number of pages:X, 57 str.
PID:20.500.12556/RUL-141740 This link opens in a new window
UDC:556.166:711.1(497.4)(043.3)
COBISS.SI-ID:122090499 This link opens in a new window
Publication date in RUL:06.10.2022
Views:1222
Downloads:141
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Secondary language

Language:Slovenian
Title:Ocena negotovosti pri izdelavi kart poplavne nevarnosti : master thesis no.: 98/II. VOI-FRM
Abstract:
Izdelava kart poplavne nevarnosti je bistvena sestavina v postopku izdelave ocene poplavne ogroženosti, saj zagotavlja ključne informacije za preventivno zmanjševanje poplavne ogroženosti, ki se v veliki meri uporablja pri prostorskem načrtovanju, obvladovanju poplavnih tveganja in ozaveščanju javnosti o nevarnosti poplav. Prostorske in časovne spremembe naravnih procesov, omejeno poznavanje fizikalnih procesov in nezadostni podatki vnašajo negotovosti v proces modeliranja poplavnih dogodkov, ki se uporablja za izdelavo kart obsega poplav in analizo poplavne nevarnosti, kar ovira obvladovanje tveganja zaradi poplav. To magistrsko delo raziskuje vpliv negotovosti v hidrološki in hidravlični parametrizaciji ter s tem povezano občutljivost hidroloških in hidravličnih izračunov in rezultatov modeliranja na kartiranje poplavne nevarnosti. Natančneje je preučen vpliv negotovosti, povezanih z obliko hidrograma pretoka in oceno konice visokovodnega pretoka ter spremenljivostjo vrednosti Manningovega koeficienta hrapavosti struge reke Vipave in poplavnega območja, na rezultate kombiniranega 1D/2D hidravličnega modela z uporabo LiDAR digitalnega modela terena v kombinaciji z geodetskimi podatki rečne struge in podrobnimi podatki o rabi tal. Analiza negotovosti in občutljivosti je bila izdelana za odsek reke Vipave, čezmejne reke, ki teče skozi Slovenijo in Italijo. Izdelana je bila primerjava obsegov poplav in prostorske porazdelitve razredov poplavne nevarnosti s hidravličnimi simulacijami območij razlivanja poplavnih voda povezanih z 10-, 100- in 500-letno povratno dobo, kot jih določa slovenska zakonodaja. Analiza je pokazala največjo občutljivost rezultatov modeliranja na spremenljivost vrednosti Manningovega koeficienta hrapavosti glavne struge v primeru 10-letne povratne dobe, ki se odraža v povečanju obsega poplavljenih površin za 45%. Pri 100- in 500-letnih poplavah je povečanje poplavljenih območij manjše in znaša 15% oziroma 11%. Poleg tega rezultati modeliranja potrjujejo velik vpliv negotovosti pri oceni visokovodne konice pretoka v primerjavi z vplivom spremenljivih vrednosti Manningovega koeficienta hrapavosti na poplavnih območjih. Ugotovljeno je bilo povečanje poplavnega območja za 9-12% ob upoštevanju vrednosti intervala zaupanja 10% in 90% statistično izvrednotenih konic pretokov za različne verjetnosti pojava poplav. V primeru spremenljivih vrednosti koeficientov hrapavosti na poplavnih območjih je bilo povečanje obsega poplavljenih območij 4-6%. Vpliv oblike hidrograma toka se je izkazal kot najmanj pomemben dejavnik pri določitvi obsega poplavljenih površin, spremenljivost obsega poplavljenih površin je znašala 2-3%. Vse zgoraj omenjene spremembe skupnega obsega poplav se odražajo v spremenljivosti prostorskega obsega razredov poplavne nevarnosti, ki niso enotne in enakomerno porazdeljene za vse razrede poplavne nevarnosti, ampak so odvisne od porazdelitev globine vode na poplavnih območjih kot prevladujočega kriterija za razvrščanje v razrede poplavne nevarnosti.

Keywords:gradbeništvo, magistrska dela, VOI, kartiranje poplavne nevarnosti, hidrogram odtoka, hidravlično modeliranje, Manningov koeficient hrapavosti, občutljivostna analiza, analiza negotovosti, reka Vipava

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