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Natural and nature based features for use in coastal protection; a UK perspective
No full textHR Wallingford is undertaking a piece of work for USACE Institute for Water Resources on the United Kingdom experience on coastal green (natural and nature-based) and gray (structural) infrastructure. The objectives of this work have been to identify principles and issues common between the USA and the United Kingdom regarding how the two governments make coastal infrastructure investment decisions, to provide case studies of overcoming engineering and governance barriers and to identify the critical success factors for coastal management, specifically in regard to natural and nature-based features. This presentation will explain the outcomes of this work and will cover aspects such as greening of grey infrastructure and greying of green infrastructure, sediment management at multiple scales, management of beach and dune systems, and natural and artificial offshore reefs
The Earth by TELEMAC
Get PDFThis article describes the development of a
highly detailed model of the Earth, based on the
TELEMAC system, applied to modelling various
physical processes including tides, storms, tsunamis and
waves. Comparisons against known global datasets
demonstrate the capability of the TELEMAC system to
bridge the gap between environmental hydraulics and
oceanography. Preliminary results in forecasting internal
tides and 3D ocean currents are also presented
Validation of a TELEMAC-3D model of a seamount
Get PDFA survey was carried out at Tropic Seamount off the
Atlantic coast of Africa. This has allowed a TELEMAC-3D
model to be constructed and validated using the measured
data. The importance of internal tides at the site and possibility of a Taylor column have been assessed
Assessing the joint probability of sea conditions: a robust approach
No full textThe design of breakwaters and other coastal structures around the UK requires the assessment of the joint probability of extreme waves and sea levels. There is a standard simplified approach applied within the UK that uses joint exceedance contours of waves and sea levels. This simplified approach can be non-conservative and lead to the under-design of coastal structures unless correction factors are applied. These limitations have been known for a number of years and alternative, more robust, methods have been applied in the past. These alternative methods are risk-based as they enable the probability of the consequence (structural or serviceability failure) to be established. The more robust methods are not, however, widely used in current practice. This paper describes the development of a statistically robust nearshore multivariate extremes data set around the coastline of England. The dataset can, in principle, be used to undertake risk-based design of structures, thereby overcoming the limitations of existing practice
Maximising the benefits of natural flood management: Examples from around Europe
No full textA meeting of the European Union Environment Ministers in March 2011 recommended that an integrated approach for the implementation of the Floods Directive and Water Framework Directive should be promoted in order to “maximise the synergies” between them. One of the main objectives of this was to identify areas where natural flood management measures (e.g. catchment water retention, river and floodplain restoration, use of Sustainable Drainage Systems, changes in land management and creation of multifunctional wetlands) can meet the aims of both the Floods Directive and Water Framework Directive. There are many measures that aim to reduce flood risk which can have multiple benefits for water quality, nature and biodiversity. River and floodplain restoration, whereby natural processes are restored, can contribute significantly to both Floods Directive and Water Framework Directive objectives. This is because of the high degree of dependency that quality indicators such as fish and invertebrates have on rivers and floodplains and the role that floodplains play in flood risk management. The Floods Directive only reached the end of its first implementation cycle in December 2015 and hence Member States generally have only limited experience to date in the coordination of the Floods Directive with the Water Framework Directive. This paper will look at the challenges faced by various countries throughout Europe including Austria, Belgium, England, Germany, Scotland and Spain that have implemented natural flood management measures which aimed to both increase biodiversity and reduce flood risk
Prediction of Gravel Beach Storm Profiles Under Bimodal Sea-States
Get PDFPresently our understanding of gravel beach response under wave attack is limited and approaches to predict gravel beach response rely on formulae and models based on a few physical modelling studies. Field and laboratory studies (Hawkes, Coates, and Jones (1998)) indicate the importance of complex wave spectra (combining swell and wind sea) in the design of gravel beach recharge schemes.
The objective of the study was to develop a data-set and a new parametric model, Shingle-B, to analyse the generic profile response of shingle beaches under bimodal wave conditions in order to increase confidence in beach cross section design. A mobile bed flume study was therefore carried out at HR Wallingford.
This paper describes both the design and the results of the 2D physical model study
Multivariate extreme value modelling of sea conditions around the coast of England
Get PDFIt is widely recognised that coastal flood events can arise from combinations of extreme waves and sea levels. For flood risk analysis and the design of coastal structures it is therefore necessary to assess the joint probability of the occurrence of these variables. Traditional methods have involved the application of joint probability contours, defined in terms of extremes of sea conditions that can, if applied without correction factors, lead to the underestimation of flood risk and under-design of coastal structures. This paper describes the application of a robust multivariate statistical model to analyse extreme offshore waves, wind and sea levels around the coast of England. The approach described here is risk based in that it seeks to define extremes of response variables directly, rather than the joint extremes of sea conditions. The output of the statistical model comprises a Monte Carlo simulation of extreme events. These distributions of extreme events have been transformed from offshore to nearshore using a statistical emulator of a wave transformation model. The resulting nearshore extreme sea condition distributions have the potential to be applied for a range of purposes. The application is demonstrated using two structures located on the south coast of England
Direct monitoring of active geohazards: emerging geophysical tools for deep-water assessments
No full textSeafloor networks of cables, pipelines, and other infrastructure underpin our daily lives, providing communication links, information, and energy supplies. Despite their global importance, these networks are vulnerable to damage by a number of natural seafloor hazards, including landslides, turbidity currents, fluid flow, and scour. Conventional geophysical techniques, such as high-resolution reflection seismic and side-scan sonar, are commonly employed in geohazard assessments. These conventional tools provide essential information for route planning and design; however, such surveys provide only indirect evidence of past processes and do not observe or measure the geohazard itself. As such, many numerical-based impact models lack field-scale calibration, and much uncertainty exists about the triggers, nature, and frequency of deep-water geohazards. Recent advances in technology now enable a step change in their understanding through direct monitoring. We outline some emerging monitoring tools and how they can quantify key parameters for deepwater geohazard assessment. Repeat seafloor surveys in dynamic areas show that solely relying on evidence from past deposits can lead to an under-representation of the geohazard events. Acoustic Doppler current profiling provides new insights into the structure of turbidity currents, whereas instrumented mobile sensors record the nature of movement at the base of those flows for the first time. Existing and bespoke cabled networks enable high bandwidth, low power, and distributed measurements of parameters such as strain across large areas of seafloor. These techniques provide valuable new measurements that will improve geohazard assessments and should be deployed in a complementary manner alongside conventional geophysical tools
A comparison of approaches to risk-based flood modelling in the US and Europe
No full textThe approach to floodplain risk management in the US has evolved around the National Flood
Insurance Program (NFIP) and as such is largely focused on establishing Flood Insurance Rate Maps
(FIRM) that specify insurance rates in zones that are anticipated to fall within the zone of inundation
that is determined to be associated with the 0.01 percent chance of occurrence during any given year
(i.e. 100-yr Flood). While this approach offers a wide range of information for floodplain managers
and communities to make decisions about how to best manage at risk portions of their communities,
it is not a truly risk-based approach to floodplain management. Furthermore, in order to sustainably
fund the US National Flood Insurance Program (NFIP), a way has to be found to determine the
actuarially based premiums which should be paid by home owners. This imperative has driven the
work that will be reported in this paper.
Risk, defined as the probability of consequence (e.g. in dollars), enables a broader understanding of:
a) the variability of flooding in time and space; b) the pathways that exist between the flooding source
and the flood prone area, including the effect of levees (flood defences); and c) the variable
probability of occurrence across the floodplain. The paper reviews various full risk based mapping
approaches that have either been proposed for the US by various organisations or already adopted in
a number of European countries and within the insurance industry. It identifies key challenges for
changing the approach in the US in terms of data requirements, methodological tool development,
upskilling and communication and concludes by setting out a tentative road map for the US to move
from the current system through to the full systems-based flood risk analysis method