SEMI-QUANTITATIVE ASSESSMENT OF DEBRIS FLOW RISKS ON HIGHWAYS

Abstract

Semi-quantitative methodology for determining the category of debris flow risks of transport infrastructure facilities is designed to detect potential debris flow vulnerable parts of highways and to assess the effects of debris flows. The results obtained through this methodology can be used to justify the sequence of repair works or the construction of means of engineering protection, monitoring measures and alert system. The technical expertise of debris flow vulnerable tracks on the Black Sea coast of the Krasnodar Territory and the calculation of flow parameters allow ranking of the formation factors in relation to each other. Each factor is awarded points in accordance with the display intensity and the impact on the road. The mutual influence of individual factors is determined by integration which is performed by combination of summation and multiplication. The main criteria of a debris flow formation are: steepness of slopes and riverbeds of watersheds, the amount of destroyed rocks elements (erosion process development degree; presence, amount and location of segments with large reserves of deposited drift), sources of the water component of flows, heights of the area, geological structure, plant cover, erosion and weathering processes intensity; information about previous mudflows (frequency of occurrence, volume of removals). The technical state of anti-mudflow and engineering protection building structures also plays an essential role in the risk assessment. Due to some damage accumulated over time there is decrease in strength and stability, the possibility of construction destruction increases. The previous sediments and the construction parts involvement creates a breakthrough wave, a significant increase in the mudflow and therefore the damage.