MAGNITUDE OF DAMAGE EVENTS ON HYDROTECHNICAL TORRENT CONTROL STRUCTURES

Abstract

The objectives of this paper address the identification and statistical analysis of the laws underlying the variability of the magnitude of the damages to torrent control structures induced by four of the most well-known events affecting their stability, resistance and durability. The research set consists of 100 torrent control structures that have continuously functioned for almost three decades in a managed torrential watershed in the forested mountainous area of Romania. In the first stage, the criteria and quantitative assessment scales regarding the magnitude of the damage that occurred during this period are set. In the second stage, a statistical analysis is performed aiming at fitting frequency distributions to the magnitude of these events. Quantification of the magnitude is presented by means of two statistical indicators (arithmetic mean and variation coefficient) as well as in the form of a theoretical function that can be used to estimate the frequency of events of various intensities over the entire functional period of the structures. On a 5-degree intensity scale (1=very low; 5=very high), three of the researched events (breakage of the terminal spur, undermining of the body, undermining of the apron) were of medium intensity, and the fourth (erosive damage or abrasion) was of low intensity. The statistical variability of the magnitude of the damage, as well as the nature of the law followed by the frequency distributions of the damage magnitudes, depends on: the nature of the event, the characteristics used for the quantification of the magnitude and the amplitude of the interval used for grouping frequencies into classes. Charlier type A and Beta laws have proved their flexibility in fitting the sequences of experimental frequencies, even if the values of the magnitude variation coefficient ranged, due to the influence of several factors, from 30% to 70%. From a practical point of view, the results can guide future monitoring and maintenance decisions concerning the type, extent and periodicity of the operations ensuring: the required performance of torrent control structures, the reinstatement of the structures affected by stream processes and the reestablishment of systems of which they are part.