Assessment of maintenance efforts and probabilities of failure at German inland waterways to advance the design of bank revetments

Abstract

Revetments protect waterways or flood defenses against erosion from waves and currents. In Germany a high percentage of about 7235 km of waterways is secured by revetments. Like many stakeholders of various infrastructures, the German Federal Waterways and Shipping Administration increasingly aims for a more economic and ecological design and maintenance strategy. Thus, new methodologies must be introduced that relate the structural condition of the revetment to resulting consequences such as required maintenance. In this paper we investigate the correlation of maintenance and revetment stability. Using the example of German inland waterways, maintenance measures conducted over at least six years are correlated with a deterministic and a probabilistic stability assessment. To account for realistic traffic loads, the stability assessment employs field measurements which provide data on ship-induced waves. It was found that at least a linear correlation between revetment stability and maintenance must be assumed. A comparison between the deterministic and the probabilistic stability assessment and thereby obtained correlations shows that less maintenance is predicted with the deterministic stability assessment. Particularly for small sample sizes and small probabilities of failure, the probabilistic approach should be favored over the deterministic approach to account for various uncertainties. In the case that only maintenance is of relevance for design considerations, the results of the probabilistic approach indicate that β = 1.3 (p_f ≈ 10^-1) may be a suitable annual target reliability.