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This work offers a detailed validation of finite volume (FV) flood models in the case where horizontal floodplain flow is affected by sewer surcharge flow via a manhole. The FV numerical solution of the 2D shallow water equations is considered based on two approximate Riemann solvers, HLLC and Roe, on both quadrilateral structured and triangular unstructured mesh-types. The models are validated against a high resolution experimental data-set obtained using a physical model of a sewer system linked to a floodplain via a manhole. It was verified that the sensitivity of the models is inversely proportional to the surcharged flow/surface inflow ratio, and therefore requires more calibration from the user especially when concerned with localised modelling of sewer-to-floodplain flow. Our findings provide novel evidence that shock capturing FV-based flood models are applicable to simulate localised sewer-to-floodplain flow interaction.

University (Katsura compus, Nishikyo-ku, Kyoto 615-8540, Japan) 2 Member of JSCE, Dr. of Eng., Prof., DPRI, Kyoto University (Yoko-oji, Fushimi, Kyoto 612-8235, Japan) 3 Member of JSCE, Dr. of Eng., Assoc. Prof., DPRI, Kyoto University (Yoko-oji, Fushimi, Kyoto 612-8235, Japan) 4 Member of JSCE, Dr. of Eng., Assis. Prof., DPRI, Kyoto University Fushimi, Japan) Recently, there have been a lot of numerical models for prediction of urban inundation damage due to heavy rainfall by using the combined drainage system. Although it is important to estimate inlet and overflow discharge through the storm drain, calculation method and formula are not clarified. Hence, in this study, the numerical model of storm water interaction between the ground surface and drainage system we have previously used is improved and validated based on physical experiments. From the comparison, they showed agreement in all the cases of steady state condition. In the unsteady state cases, it was found that simulation results agreed well with experimental results of the ground inundation start time and the maximum inundation depth as well as the water level increase process. However, piezometric head reproduced small differences when the downstream water level was decreased. It was judged that was caused by inadequate consideration of exit and entrance head loss between the tank and pipe.

The Preissmann slot model is one of the most widely used models to conceptualize both free-surface and pressurized flows in urban drainage systems. Despite its simplicity and wide range of applications, numerical solutions of the Preissmann slot model suffer from the spurious oscillations, especially when flow conditions switch from free-surface flow to pressurized flow. To overcome this problem, a new hybrid numerical flux solver of the Preissmann slot model is proposed herein, in which the upwind flux solver is combined with the centered flux solver. Numerical experiments are conducted for multiple flow conditions such as typical filling, pipe-filling, and transition-flow conditions. The numerical results indicate that the proposed scheme generally outperforms the conventional flux schemes for various hydraulic conditions and wave velocities. The proposed scheme should be useful to further enhance integrated urban water modeling in which transient mixed flow conditions significantly impact the simulation accuracy during extreme floods.

To obtain accurate flood analysis results, research using high-resolution Digital Elevation Models is becoming important and studies to increase the calculation speed and accuracy are being performed. Numerous researchers have studied parallelisation techniques to improve the accuracy of urban flood analysis by grid resolution and by 1D/2D coupled models. However, there have been few studies on the effects of interacting discharge between the surface and sewerage system on urban flooding analysis using parallelisation techniques. Therefore, in this study, the efficiency of the OpenMP parallelisation technique was investigated according to grid size and type to analyse the influence of the distribution of storm drain boxes on the results of fully integrated 1D/2D urban inundation modelling focused on the interacting discharge between the surface and storm drain boxes. K E Y W O R D Sintegrated 1D/2D, interacting discharge, OpenMP parallelisation, urban inundation modelling

The floods associated with the effects of an incoming tropical cyclone have an immense effect in the Philippines, especially with respect to agriculture, industry, livelihood, and public safety. Knowledge of how such storm surge flooding can affect the community is therefore of great importance. In this study, the mechanisms behind Typhoon Haiyan’s anomalous storm surge flooding in 2013, which resulted in more than 6300 casualties and 2.86 billion USD worth of damage in the Philippines, were investigated. The Japan Meteorological Agency (JMA) storm surge model and the FLO-2D flood model were used to simulate Typhoon Haiyan’s storm surge height and the extent of inundation, respectively. The storm surge input data were obtained from JMA typhoon data, and the digital terrain models used were gathered from the airborne interferometric synthetic aperture radar data. The model’s accuracy was also validated using field validation data of the extent of the observed storm surge in affected coastal areas. Topographical analysis of the inundated regions showed the effects of coastal shape, elevation, and position relative to the typhoon’s approach angle on storm surge flow depth and velocity. Storm surge maximum velocity appears to increase as the fluid flows to an increasingly elevated area. Observing fluid velocity in a coastal area with uniform storm surge discharge from all directions also showed that flow velocity tends to increase at the center. Greater flood depths were experienced in areas with lower coastal elevation and not directly located at the coast, compared to higher elevation coastal areas. Greater extents of storm surge flooding are expected in coastal areas that have a concave shape, as fluid is more likely to be dispersed when hitting a convex coast. Extents are likewise observed to be greater in coastal regions that are located perpendicular to the direction of the typhoon. The research also validated the option of using a combination of typhoon and flood models to simulate the inundation flooding caused by extreme weather events.

University (Katsura compus, Nishikyo-ku, Kyoto 615-8540, Japan) 2 Member of JSCE, Dr. of Eng., Prof., DPRI, Kyoto University (Yoko-oji, Fushimi, Kyoto 612-8235, Japan) 3 Member of JSCE, Dr. of Eng., Assoc. Prof., DPRI, Kyoto University (Yoko-oji, Fushimi, Kyoto 612-8235, Japan) 4 Member of JSCE, Dr. of Eng., Assis. Prof., DPRI, Kyoto University Fushimi, Japan) Urban inundation has particularly been reported to lead to extensive property damage and casualties due to the concentration of people and properties in highly urbanized areas. The sewer system is one of the most important components of urban inundation analysis. The numerical simulation model developed for this study consists of a 1D slot model of sewer pipe flow, and estimates head loss between manhole and sewer pipes based on the rigid column theory. In order to obtain validation data, the fundamental laboratory experiments were conducted so as to estimate the effects of head loss depending on different manhole shapes with no benching and no invert. First, straight case experiments were conducted to evaluate the head loss with circular and square type manhole shapes under the steady state condition. Next, unsteady state experiments were conducted. Finally, a numerical simulation model was tested and validated to confirm the model's applicability in using head loss coefficients obtained from laboratory experiments. Simulation results demonstrated high agreement with experimental data, so the newly developed model can be used to analyze urban sewerage systems.

The applicability of the stage-fall-discharge (SFD) method in combination with acoustic Doppler velocity meter (ADVM) data, upstream of a hydraulic structure, specifically, the Sejong-weir located in the Geum River, Korea, was examined. We developed three rating curves: a conventional simple rating curve with the data measured using an acoustic Doppler current profiler (ADCP) and floating objects, an SFD rating curve with the data measured using the ADCP and floating objects, and an SFD rating curve with the data measured using an ADVM. Because of the gate operation effect, every rating curve involved many uncertainties under 1000 m3/s (3.13 m2/s, specific discharge). In terms of the hydrograph reconstruction, compared with the conventional simple rating curve, the SFD developed using ADVM data exhibited a higher agreement with the measured data in terms of the pattern. Furthermore, the measured discharge over 1000 m3/s primarily ranged between 97.5% and 2.5% in the graph comparing the ratio of the median and observed discharge. Based on this experiment, it is confirmed that the SFD rating curve with data to represent the backwater effect, such as ADVM data, can reduce the uncertainties induced by the typical rating curve