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More than 20 years after the 2000 Stože Landslide that devastated the village of Log pod Mangartom in NW Slovenia, this paper gives a review of the short-term response to and disaster relief provided for this catastrophic event, and further summarises this events effects on Slovenias efforts to improve its system of preventing natural disasters caused by various forms of landslides. Recent advances in reducing landslide disasters in Slovenia after 2000 are presented, including hazard and risk maps for landslides, rockfalls, and debris flows based on modern methodologies. Also, a short overview is given of Slovenian international cooperation on natural disasters. The developments in the landslide disaster risk reduction policy have unfortunately been less obvious in terms of the state taking preventive measures by adopting relevant legislation for adequate spatial planning.Po več kot 20 letih od plazu Stože leta 2000, ki je opustošil vas Log pod Mangartom v SZ Sloveniji, ta članek podaja pregled kratkoročnega odziva in pomoči ob nesreči ter nadalje povzema vpliv tega dogodka na prizadevanja v Republiki Sloveniji za izboljšanje sistema za preprečevanje naravnih nesreč, ki jih povzročajo različne oblike zemeljskih plazov. Predstavljen je nedavni napredek na področju zmanjševanja nevarnosti delovanja zemeljskih plazov v Sloveniji po letu 2000, vključno s kartami nevarnosti in ogroženosti za zemeljske plazove, skalne podore in drobirske tokove, ki so bile izdelane na podlagi sodobnih metodologij. Podan je tudi kratek pregled mednarodnega sodelovanja Slovenije na področju naravnih nesreč. Razvoj politike zmanjševanja naravnih in drugih nesreč zaradi delovanja zemeljskih plazov je bil žal manj očiten na področju preventivnih ukrepov države, ki bi s sprejetjem ustreznih zakonskih aktov okrepila preventivno delovanje z njihovo uporabo v ustreznih postopkih prostorskega načrtovanja.

Alluvial (torrential) fans, especially those created from debris-flow activity, often endanger built environments and human life. It is well known that these kinds of territories where human activities are favored are characterized by increasing instability and related hydrological risk therefore, treating the problem of its assessment and management is becoming strongly relevant. The aim of this study was to analyze and model the geomorphological aspects and the physical processes of alluvial fans in relation to the environmental characteristics of the territory for classification and prediction purposes. The main geomorphometric parameters capable of describing complex properties, such as relative fan position depending on the neighborhood, which can affect their formation or shape, or properties delineating specific parts of fans, were identified and evaluated through digital elevation model (DEM) data. Five machine learning (ML) methods, including a hybrid Euler graph ML method, were compared to analyze the geomorphometric parameters and physical characteristics of alluvial fans. The results obtained in 14 case studies of Slovenian torrential fans, validated with data of the empirical model proposed by Bertrand et al. (2013), confirm the validity of the developed method and the possibility to identify alluvial fans that can be considered as debris-flow prone.

V disertaciji je obravnavana problematika ocenjevanja nevarnosti zaradi delovanja drobirskih tokov na hudourniških vršajih. Glavni poudarek raziskave je problematika, ki se je v preteklih raziskavah izkazala za težavno in sicer gre za klasifikacijo hudourniških območij, iz katere bi bilo razvidno ali je izbrano hudourniško območje nagnjeno k delovanju drobirskih tokov. Na izbranem nevarnem območju pa ocenjevanje magnitude potencialnega drobirskega toka in določeni deli postopka matematičnega modeliranja gibanja drobirskih tokov, predvsem povezani z reološkimi karakteristikami mešanice in vplivom topografskih podatkov o terenu, ki so osnova za izdelavo modela. Disertacija se v prvem delu osredotoča na določanje parametrov hudourniških območij in analizo različnih metod za njihovo klasificiranje. Na podlagi analize večih metod je predlagana klasifikacija na nevarna, prehodna in nenevarna hudourniška območja, ki je predstavljena na izbranem testnem območju. V analizo smo vključili v tujini in Sloveniji razvite metode in orodja s tega področja. V drugem delu disertacije je poudarek na ocenjevanju magnitude potencialnega drobirskega toka z modelom LS-Rapid, ki je uporabljen na hudourniškem območju Bele, kjer je prikazana uporaba modela za določanje nestabilnih območij na nivoju celotnega hudourniškega območja. Uporaba modela za ocenjevanje količine sproženega materiala pa je prikazana na primeru plazu Stože, kjer je izvedena analiza plazu, ki se je sprožil novembra 2000. Za določanje parametrov modela LS-Rapid, ki jih za potencialne zemeljske plazove ni možno natančno določiti, smo podali napotke o določanju mejnih vrednosti, ki so uporabne za modeliranje potencialnih zemeljskih plazov. Zaradi modeliranja gibanja drobirskih tokov na hudourniških vršajih so bile za potrebe določanja reoloških karakteristik drobirskega materiala izvedene raziskave v geomehanskem laboratoriju na vzorcih materiala, ki smo ga odvzeli na izvornem mestu plazu Stože. Na podlagi testiranja smo podali navodila, kako za model Flo-2D določati reološke karakteristike potencialnih drobirskih tokov. Prikazana je tudi analiza vpliva različnih topografskih podatkov na rezultate modeliranja gibanja drobirskih tokov. Uporabljeni so bili tako komercialni kot tudi javni topografski podatki predvsem uporabni so se izkazali najnovejši LiDAR-ski podatki. Na podlagi lastnih rezultatov in predlogov je na koncu disertacije podan predlog metodologije za ocenjevanje nevarnosti zaradi delovanja drobirskih tokov na hudourniških vršajih in usmeritve za nadaljnje delo. PhD thesis deals with debris flow hazard assessment on torrential fans. Its main focus is on the known problems pointed out with the already performed research, such as is the way of preliminary classification of torrential catchments to determine those, which are prone to trigger debris flows, furthermore, how to estimate magnitudes of potential debris flows triggered in these torrential catchments, and finally, open questions with regard to debris-flow mathematical modeling on torrential fans, especially their rheological characteristics to be used in mathematical models and how topography influences modelling results. In the first part, we focus on geomorphological parameters of torrential catchments and various methods for classification of torrential catchments prone to debris-flow triggering. Based on analysis of the selected methods, a new classification method was proposed for classification of debris-flow prone catchments, transitional catchments and catchments with no debris- flow hazard. This new method was then tested in selected torrential catchments in Slovenia. For debris-flow magnitude assessment, we applied the LS-Rapid triggering model. With its application in the Bela torrential catchment (NW Slovenia), we could identify several active landslides and potentially unstable areas, which could under unfavorable conditions turn into active landslides and trigger debris flows. A detailed study and debris-flow modeling was then carried out on the Stože landslide (NW Slovenia), which was triggered in November 2000. For debris-flow model parameters, which cannot be determined with sufficient reliability without analyzing soil samples in detail in a geomechanical laboratory, we proposed an estimation of their limit values, which can be used for potential landslide modeling. Soil samples were taken from the Stože landslide source area for testing in a geomechanical laboratory. In this way, rheological properties of a potential debris flow could be determined, and then used in debris-flow mathematical routing model on a torrential fan. Based on our own laboratory study, and additionally testing of the Flo-2D model, we proposed instructions how to assess potential debris-flow rheological characteristics. Furthermore, with the Flo-2D model we tested the influence of different topographical datasets on debris-flow modeling results. We applied different publicly available topographical data and commercial LiDAR data to develop DEM with different resolutions. The debris-flow modeling results, obtained by using new public available LiDAR based data and the Flo-2D model, turned out to be very /plausible. Finally, we comprise single steps described in previous sections into a new methodology for debris-flow hazard assessment on torrential fans, culminating in the debris-flow hazard mapping. The PhD thesis ends up with some recommendations for further research in this field.

The societal risk related to rainfall-triggered rapid debris flows is commonly managed in urbanized areas by means of early warning systems based on monitoring of hydrological parameters (such as rainfall or soil moisture) and analysis of thresholds values. This paper deals with physically-based modelling of ash-fall pyroclastic soil coverings involved in debris flows along mountain slopes nearby the Somma-Vesuvius volcano (Campania, southern Italy), which represent one of the major geohazards of Italy. The methods adopted combine deterministic approaches at the site-specific and distributed scales to estimate Intensity-Duration rainfall thresholds triggering debris flows. The first approach is based on the reconstruction of detailed physical models of ash-fall pyroclastic soil coverings in representative source areas of debris flows and on the related hydrological and slope stability modelling. The second is focused on a regional distribution model of ash-fall pyroclastic soils over mountain slopes surrounding the Somma-Vesuvius volcano, which takes into account total thicknesses of pyroclastic coverings and variable stratigraphic settings. For both, effects of different initial antecedent hydrological conditions, associated with summer and winter, are considered.

V nalogi je najprej pripravljen pregled in opisane različne klasifikacije masnih gibanj, med katere se uvrščajo tudi drobirski tokovi. Drobirski tokovi so predstavljeni podrobneje. Opisane so njihove lastnosti in prikazana klasifikacija glede na nastanek, velikost in hitrost. Opisane so tudi glavne razlike med drobirskimi tokovi in drugimi masnimi gibanji. Nadalje je predstavljen model Flo-2D in opisana njegova uporaba, način delovanja in postopek izdelave modela drobirskega toka. Opisane so dosedanje izkušnje z modeliranjem drobirskih tokov v Sloveniji in uporaba različnih matematičnih modelov, vključno s Flo-2D. Opisana je slovenska zakonodaja na področju varstva pred poplavami in erozijo, kjer je predpisana metodologija za izdelavo opozorilnih kart, kart nevarnosti in kart ogroženosti zaradi delovanja poplav in erozije. Predlagan je način izdelave opozorilnih kart in podrobnejših kart nevarnosti zaradi delovanja drobirskih tokov, pri čemer so drobirski tokovi razdeljeni na hudourniške in pobočne. Glavni del naloge je uporaba matematičnega modela Flo-2D pri modeliranju drobirskih tokov na hudourniških vršajih z uporabo javno dostopnih podatkov. Raziskava je opravljena na hudourniških vršajih pritokov Save Dolinke. V občutljivostni analizi modela je analiziran vpliv nastavitev kontrolnih parametrov modela, pozicije vhodnega hidrograma, Manningovega koeficienta hrapavosti ng, velikosti računskih celic, različnih reoloških karakteristik in vpliv različnih načinov modeliranja objektov na hudourniških vršajih. Obravnavana je možnost uporabe rezultatov modelov, izdelanih z uporabo javno dostopnih vhodnih podatkov za pripravo podrobnejših kart nevarnosti, kar bi pomenilo, da je take karte možno pripraviti z relativno majhnimi stroški, brez dragih dodatnih raziskav. Prikazana je tudi možnost izdelave kart nevarnosti z vmesnikom, ki je vgrajen v model Flo-2D. Kot največja pomanjkljivost med vhodnimi podatki so se izkazali podatki o terenu DMV5, kjer je zaradi avtomatske izdelave vsebovanih veliko napak o topografiji terena, ki lahko bistveno vplivajo na rezultate modela. Sicer pa je večina ostalih uporabljenih vhodnih podatkov dovolj dobro določljiva, da bi bil predlagani način dela uporaben za pripravo kart nevarnosti. IV The present thesis begins with an overview and different classifications of mass movements. Debris flows, one type of mass movements, are described in detail. First, their characteristics are presented and also classified according to the type of triggering, magnitude and velocity. The main differences between the debris flows and other mass movements are also described. In addition, the mathematical model Flo-2D is described. Its use, functioning and procedure of modeling debris flows are presented, as are the previous experiences with debris flow modeling in Slovenia and the use of different mathematical models, including Flo-2D. In the following chapter, the Slovene legislation in the area of flooding and erosion hazard is described. This legislation prescribes the methodology of preparing the preliminary hazard maps, hazard maps and risk maps due to the influence of flooding and erosion. The thesis proposes a protocol of preparing the preliminary hazard maps and hazard maps due to the debris flow effects. Debris flows are divided into torrential and slope debris flows. The main part of the thesis is dedicated to the practical use of the mathematical model Flo-2D in debris flow modeling of torrential fans using only the publicly available data. The alpine valley of Sava Dolinka River was selected as a test region. In the sensitivity analysis of the Flo-2D model, the influence of different parameters was tested: the control parameters settings of the model, the position of the incoming hydrograph, the Manning roughness coefficient, the computational grid size, different rheological characteristics and the influence of different ways of modeling objects on torrential fans. The possibility of using the results of the models made with publicly available data is evaluated in preparing hazard maps. This method would enable the preparation of hazard maps with relatively low costs and without the expensive extra surveys. The possibility of preparing hazard maps using an application proposed in the Flo-2D model is also presented. The topographic data DEM5 turned out to be the main deficiency of all the input data used in the research, as they can dramatically affect the model results and hazard area assessments. The rest of the applied model input data can be defined well enough to be efficient in preparing the hazard maps the way it is described in this thesis.