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Modelling approaches to inform and improve community resilience and evacuation response.
No full textA new standard for flood resistance and resilience of buildings: new build and retrofit
No full textWith around three million properties in England affected by severe weather-driven surface water (pluvial) flooding, and the number likely to increase as a result of climate change, it is important that homeowners and businesses are encouraged to take steps to minimise the effects of future flood events. This is where property-level protection and building resilience measures are important. However, stakeholders will continue to need assistance and advice on how to select appropriate measures. Based on laboratory testing and other desk studies, a guidance document was developed in 2007 giving advice on resilient approaches for new buildings. This was adopted by many organisations, to inform measures that could be used, particularly to deal with residual flood risks, which cannot always be designed out. Since 2009, through the “Statement of Principles” with the insurance industry and the NPPF, unsuitable development has been discouraged in areas at high flood risk. However, with the increased awareness of the need to deal with surface water for existing housing stock, a new standard was needed. Therefore the British Standards Institution has developed a new standard (BS 85500) that updates and extends the guidance document, including retrofitting flood resistance and resilience measures to existing properties. This paper outlines the Standard’s contents and some of the key issues associated with its development
Impact of the 2011 tsunami on the littoral system around offshore breakwaters on Sendai Coast
Get PDFAfter the 2011 Great East Japan Earthquake Tsunami, littoral system on Sendai Coast have been changing due to tsunami-induced highly non-equilibrium condition along the coast. In order to clarify the modification of littoral environment and its subsequent recovery on Sendai Coast, analysis of shoreline change has been carried out. In this study, the shoreline was extracted from frequently captured aerial photographs from 2009 until now, and analysis using an empirical orthogonal function (EOF) method was conducted. It is seen that the shoreline retreated greatly due to tsunami event. In particular, tombolo which existed behind the offshore breakwater completely disappeared due to the tsunami. Total of contribution of the 1st and 2nd EOF components is more than 70%. It is concluded that the 1st component originated from cross-shore sediment movement, while the 2nd component represents longshore sediment transport. Although the 1st component shows only slight modification after the tsunami, the 2nd component resulting from a longshore sediment transport shows distinct change after the tsunami around the offshore breakwaters
The stability of a block mattress in a propeller induced jet
Get PDFPropeller jets can have a damaging effect on bed, bank and quay structures. A block mattress is one of the various types of bed protection which can be applied to prevent the development of scour holes and subsequent undermining of bed, bank or quay structures. However, not much is known about the stability of block mattress in propeller induced loads. One of the design guidelines which can be used is the formula by Pilarzcyk, in combination with an expression for the dispersion of the propeller jet. To assess the validity of this approach laboratory experiments were performed on the stability of a block mattress in a propeller jet. The model setup comprised a non-sloping horizontal bed and a single horizontal propeller at a certain elevation above the bed. In the test section ripples were applied to mimic the typical unevenness of the bed. Fur-thermore, a distinction was made within the test programme between an ‘open edge’, i.e. an outer edge of the protection, and a ‘closed edge’, i.e. a transition between mattresses. According to the test results, the presently available design guidelines for the stability of a block mattress in a propeller jet may under predict the required thickness of an open and closed edge of a mattress. Furthermore, these guidelines may not yet cover all related aspects correctly, such as the influence of the height of the propeller and the distinction between an open or closed edge
The influence of upstream weir slope on live-bed scour at submerged weir
Get PDFShape variation of submerged weirs can change local flow patterns and sediment transport. The aim of this study is to quantify and compare the local scour at weirs with different upstream face slopes, under submerged flow and live-bed conditions. Experiments were carried out on 30 mm high weirs in a tilting, sediment recirculating flume with 0.26 mm uniform sediment. 24 experiments were undertaken involving four different upstream weir face angles (30˚, 45˚, 60˚ and 90˚ to the horizontal) and six flow intensities. Two webcams were employed to observe upstream aggradation and the local scour on both sides of the weir. The results indicate that a gentler upstream weir slope reduces the upstream scour depth at the submerged weir, for upstream weir face angle greater than 45˚. The results also show that the downstream scour depth is independent of the upstream weir slope
Numerical investigation of the particle skeleton of widely graded soils prone to suffusion
Get PDFThe soil structure affects directly the capability of distributing and transmitting forces between its particles. Thus, the particle arrangement dictates the performance of soil under hydraulic and dynamic loads. This paper describes an analysis method in which the skeletal force chains of the particle assembly (packing) can be identified based on Discrete-Element-Method (DEM) modelling. For the simulations the software LIGGGHTS is used. A widely graded particle size distribution (PSD) is investigated to find correlations between PSD and the micromechanical properties of the particle assemblies. These PSD is based on common internal stability criteria prone to suffusion.
The different roles of fractions of the PSD in packings and the force chains under specified load are analysed. Therefor a packing is generated with the Modified-Force-Biased-Algorithm (MFBA). A method based on the bimodality of widely graded PSDs is proposed to differentiate the soil skeleton and the fill of packings of such a PSD. Particle contact number and contact forces are evaluated to identify the amount of loose particles, which are potentially mobile particles. The influence of the packing homogeneity on its skeleton is also addressed. The described method provides a better understanding of the soil structure as well as of internally stability of widely graded soil
Propagation Modes of 3D Scour below a Submarine Pipeline in Oblique Steady Currents and Waves
Get PDFThis paper presents experimental results on 3D scour propagation along a pipeline under oblique-incidence currents and waves. Different modes of 3D scour propagation were discovered after the local scour was initiated below the pipeline. These modes include scour propagation throughout the whole pipeline, onset of scour at multiple locations due to piping, termination of scour propagation induced by backfill and no scour propagation. The critical conditions for these scour propagation modes were determined in terms of flow incident angle, embedment depth and Shields parameter (or KC number)
A Cartesian cut cell based two-way strong fluid-solid coupling algorithm for 2D floating bodies
No full textIn a recent paper Kelly et al. (2015) [PICIN: A Particle-In-Cell solver for incompressible free surface flows with two-way fluid–solid coupling. SIAM Journal on Scientific Computing 37 (3), B403–24.] detailed the PICIN full particle Particle-In-Cell (PIC) solver for incompressible free-surface flows. The model described in that paper employed a tailored version of the Distributed Lagrange Multiplier (DLM) method for the strong coupling of fluid–solid interaction. In this paper we propose an alternative strong fluid–solid coupling algorithm based on a modification to the cut cell methodology that is informed by the variational approach. The solid velocity flux/integral on the boundary is expressed purely in terms of pressure leading to a revised pressure Poisson equation that is discretised in a finite volume sense. This approach allows the PICIN model to simulate the motion of floating bodies of arbitrary configuration. 2D test cases involving floating bodies with one or more degrees of freedom (DoF) are used to validate the modified PICIN model. The results presented show that the modified PICIN model is able to both efficiently and robustly predict the motions of surface-piercing floating structures under either regular or extreme wave action
Using OpenMI and a Model MAP to integrate WaterML2 and NetCDF data sources into flood modelling of Genoa, Italy
No full textExtreme hydrometeorological events such as flash floods have caused considerable loss of life and damage to infrastructure over recent years. Flood events in the Mediterranean region between 1990 and 2006 caused over 4,500 fatalities and cost over €29 billion in damage, with Italy one of the worst affected countries. The Distributed Computing Infrastructure for Hydro-Meteorology (DRIHM) project is a European initiative aiming at providing an open, fully integrated eScience environment for predicting, managing, and mitigating the risks related to such extreme weather phenomena. Incorporating both modeled and observational data sources, it enables seamless access to a set of computing resources with the objective of providing a collection of services for performing experiments with numerical models in meteorology, hydrology, and hydraulics. The purpose of this article is to demonstrate how this flexible modeling architecture has been constructed using a set of standards including the NetCDF and WaterML2 file formats, in-memory coupling with OpenMI, controlled vocabularies such as CF Standard Names, ISO19139 metadata, and a Model MAP (Metadata, Adaptors, Portability) gateway concept for preparing numerical models for standardized use. Hydraulic results, including the impact to buildings and hazards to people, are given for the use cases of the severe and fatal flash floods, which occurred in Genoa, Italy in November 2011 and October 2014