A Well-Balanced and Fully Coupled Noncapacity Model for Dam-Break Flooding

The last two decades have seen great progress in mathematical modeling of fluvial processes and flooding in terms of either approximation of the physical processes or dealing with the numerical difficulties. Yet attention to simultaneously taking advancements of both aspects is rarely paid. Here a well-balanced and fully coupled noncapacity model is presented of dam-break flooding over erodible beds. The governing equations are based on the complete mass and momentum conservation laws, implying fully coupled interactions between the dam-break flow and sediment transport. A well-balanced Godunov-type finite volume method is used to solve the governing equations, facilitating satisfactory representation of the complex flow phenomena. The well-balanced property is attained by using the divergence form of matrix related to the static force for the bottom slope source term. Existing classical tests, including idealized dam-break flooding over irregular topography and experimental dam-break flooding with/without sediment transport, are numerically simulated, showing a satisfactory quantitative performance of this model

Scour around submerged spur dikes with flexible mattress protection

Flume experiments examining the effects of a flexible mattress on bed scour around spur dikes were conducted. Results showed that scour induced subsidence damage to the flexible mattress. If the width of flexible mattress, B, was insufficient, then failure of the spur dike may occur. Results also revealed that (1) scour depth decreased as the area of the protective domain around the spur dike increased (e.g., it reduced 30%, from 20 to 14 cm, as the width B increased from 0 to 0.35 m), and (2) higher approaching velocities resulted in deeper scour holes. On the basis of the experimental data and dimensional regression analysis, empirical formulas were proposed for calculating scour depth and the extent of the scour hole. The formulas were then used to obtain the optimum flexible mattress width

Inland Waterway Infrastructure Maintenance Prediction Model Based on Network-Level Assessment

Maintenance decision optimization based on network-level assessment has a long history in road transportation infrastructure and has greatly assisted management departments in saving in expenditure on maintenance costs. However, its application and research in water transportation infrastructure have been lacking. This paper aims to design a predictive model for waterway improvement building maintenance based on network-level assessment and provide a new solution for optimizing the allocation of limited maintenance funds for inland waterway infrastructure. The proposed network-level assessment framework and predictive model comprise data collection, maintenance prediction, and maintenance decision modules. A small time-series dataset was constructed based on the classification proportions of improvement building technical conditions in the jurisdiction of the Yangtze River trunk waterway over the past five years. The two-parameter moving average method was transformed into a single-parameter “jurisdiction moving average method” to suit the characteristics of the dataset. Three models, namely the jurisdiction moving average (JMA), the linear regression (LR), and the quadratic curve regression (QCR) models, were employed to perform calculations on the dataset, which were evaluated using t-tests and error analysis. The research results indicated that both the JMA and LR models showed good overall performance and were recommended for use. Especially, the confidence intervals of the JMA model increased the credibility of the prediction results, making it the ideal choice. This study also found that the inland waterway maintenance prediction technology based on the network-level evaluation has higher overall efficiency than the known existing technologies. The proposed predictive model allows for a simple and rapid assessment of the overall risk status of regional waterway facilities and is easy to promote and apply

New experimental dataset for partial dam-break floods over mobile beds

<p>An experimental investigation is presented on partial dam-break floods over mobile beds, with different bed sediment compositions and initial upstream and downstream water levels. Detailed measurements were carried out, including water level evolution, final bed topography and bed surface sediment composition. Intense scour occurred immediately downstream from the dam, followed by significant deposition and small bed forms which were only observed in cases with non-uniform sediment. Also, final bed sediment surface showed a general coarsening trend in the intense scour and deposition areas and a coarse-fine-coarse structure in the remaining reach with small bed forms. The effects of the bed sediment composition and of the difference between initial upstream and downstream water levels on bed deformation are evaluated. This work facilitates new understanding of dam-break floods over mobile beds especially with non-uniform sediment, and provides a new experimental dataset which can be exploited to underpin the development of mathematical models.</p