Benchmarking 2D hydraulic models for urban flood simulations

This paper describes benchmark testing of six two-dimensional (2D) hydraulic models (DIVAST, DIVASTTVD, TUFLOW, JFLOW, TRENT and LISFLOOD-FP) in terms of their ability to simulate surface flows in a densely urbanised area. The models are applied to a 1·0 km × 0·4 km urban catchment within the city of Glasgow, Scotland, UK, and are used to simulate a flood event that occurred at this site on 30 July 2002. An identical numerical grid describing the underlying topography is constructed for each model, using a combination of airborne laser altimetry (LiDAR) fused with digital map data, and used to run a benchmark simulation. Two numerical experiments were then conducted to test the response of each model to topographic error and uncertainty over friction parameterisation. While all the models tested produce plausible results, subtle differences between particular groups of codes give considerable insight into both the practice and science of urban hydraulic modelling. In particular, the results show that the terrain data available from modern LiDAR systems are sufficiently accurate and resolved for simulating urban flows, but such data need to be fused with digital map data of building topology and land use to gain maximum benefit from the information contained therein. When such terrain data are available, uncertainty in friction parameters becomes a more dominant factor than topographic error for typical problems. The simulations also show that flows in urban environments are characterised by numerous transitions to supercritical flow and numerical shocks. However, the effects of these are localised and they do not appear to affect overall wave propagation. In contrast, inertia terms are shown to be important in this particular case, but the specific characteristics of the test site may mean that this does not hold more generally

Breach flow discharge prediction - Analysis of USDA breach flow dataset

This report concerns the analysis of flow/discharge measurements obtained from a set of 441 \u93rigid breach\u94 models constructed between 22/07/1996 and 10/12/1998 at the Agricultural Research Service of the United States Department of Agriculture (USDA) in Stillwater, Oklahoma, US, by G.J. Hanson and colleagues. Each model consisted of a rigid plywood dam cut by a rigid breach. The program of experimental research was aimed at improving models of prediction of discharge through breached embankments, which is the first stage in the prediction of the hydraulic quantities of relevance to embankment erosion and sediment transport in breaches. In contrast with a previous analysis by Temple and Hanson of a subset of the data which consisted in calibrating existing weir discharge prediction equations or a combination of weir equations to obtain a best fit of the measured discharges, the work reported herein concentrates mainly on 1) verifying established weir equations and published guidance on the parameterisation of these equations using the USDA laboratory dataset, 2) testing an approach consisting in combining two weir equations and using the dataset to understand its limitations (the dataset also contains >5000 images which help understanding the physical processes involved in each combination of geometry and flow), 3) using the dataset to understand complex flow patterns observed that are of relevance to embankment breach flow, and 4) suggesting ways in which weir flow equations could be adapted to predict flow in various breach shapes.Floodsit

Comparaison au Large White de 4 races locales porcines françaises pour les performances de croissance, de carcasse et de qualité de la viande

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