The torrential catchments located on the northern slopes of Belasitsa Mountain (SW Bulgaria), in the area of Petrich town were affected by an intense rainfall event in December 2021 that triggered a cascade of hazard processes like floods, landslides, debris flows/floods that caused major damage to the road network, properties, and buildings, showing the urgent need to take hazard and risk assessment and mitigation measures. For assessment purposes, we perform field and UAV-based analysis, and mapping of the affected areas, the geomorphological changes after the flooding event, and the different types of identified mass-wasting processes. We also investigated the effects of early December 2021 heavy rain on a regional scale.

No abstract

The Ribnishka River watershed, located on the southern slopes of Ograzhden Mountain is known for the repeated torrential events in the last few decades. In this paper, we represent a preliminary assessment of the debris floods and debris flows hazard in the Ribnishka River watershed. For this purpose, the topographic conditions in the watershed are considered, the source, transport, and deposition zones are characterized, as well as the observed sediment deposits in the river valley. The obtained results could be used in the development of risk management plans, but also provide new information on the development of debris floods and debris flows in this part of the country.

The Botevgrad basin is one of the numerous Late Pliocene–Quaternary basins developed over the Balkanide orogen. The basin is developed in the West Balkan tectonic zone and on the northern slopes of the Stara Planina Mountain along the Plakalnitsa fault zone, the front of the orogen. The basin was interpreted as half-graben formed on the SW block of the Dragoybalkan fault, considered as the Plakalnitsa fault zone’s extensionally reactivated roots. Our data suggest that the basin formation is more complicated and all basin boards are fault predestined. The boards are morphologically well prominent and their geometry is a result of the reactivated older faults’ segmentation, combined with the different rheology of the basement lithologies, mainly Palaeozoic low-grade metamorphites and intruded into them syn- to post-metamorphic granitoids. The distribution of the numerous depocentres, the orientation of drainage systems, watershed shape and depositional system migration indicate polyphasic basin evolution. The basin shape and other data, such as criteria for sense of shearing, and intrabasinal push-up blocks’ rotation, suggest that the Botevgrad basin should be interpreted as pull-apart basin.

No abstract