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Addressing Water in National Adaptation Plans - water supplement to the UNFCCC NAP technical guidelines
No full textUrgent transformational change is required to avoid global catastrophe and limit the damage from climate risks. The Intergovernmental Panel on Climate Change warns that the window of opportunity to make changes is closing fast. If current emissions trajectories continue, global temperature rise compared to preindustrial levels could surpass 1.5°C in as little as 12 years, beyond which significantly worse climate risks threaten to perpetuate massive poverty for hundreds of millions of people, as well as generate irreversible changes in vital ecosystems. Most at risk are the world’s poorest, living in countries with weak water governance systems, weak institutions, inadequate regulatory regimes, and poor water infrastructure.
Water is a crucial environmental resource central to national economic development and livelihoods activities, alongside providing a range of context-dependent direct and indirect benefits, be they cultural, spiritual, environmental, or social. Water is also a critical pathway through which countries encounter climate risks, in terms of slow-onset droughts, acute floods, and other such disasters. Least Developed Countries in particular may lack adaptation capacities to harness the beneficial aspects of water under a changing climate, or to mitigate water-related climate risks.
See also: https://www.gwp.org/globalassets/global/gwp_napleaflet.pd
Effectiveness of natural flood management measures
No full textNatural flood management (NFM) is the approach that considers flood management measures that work with natural processes to reduce flood risk. Although there is an increasing number of examples of its application the effectiveness of the different measures is not yet fully understood.
We present an approach to investigate the performance of NFM measures and provide evidence on their effectiveness to reduce flooding. We applied our approach on a case study catchment, the Littlestock Brook in West Oxfordshire in UK, a small rural catchment that was flooded several times in the past. The physical features of a range of NFM measures were discretely represented with a 2D hydraulic model. The reduction of peak flows and water volumes generated by different storm events were estimated in order to assess the effectiveness of NFM measures and to assess their contribution to reducing flood risk. The results obtained therefore demonstrate the effectiveness of NFM measures
International guidance on use of natural and nature-based features in flood and coastal management
No full textNatural and Nature-Based Features (NNBF) have been used for decades to support a variety of objectives in coastal and riverine systems. Some types of NNBF, such as river restoration, use of bio-engineering, wetlands and beach and dune projects, have been a longstanding part of flood risk reduction strategies in Europe, the United States and elsewhere. However, stimulated by the outcomes of recent major storm events, there has been a growing interest in developing a more technically sound engineering approach to support the ‘mainstreaming’ of all types of NNBF into more comprehensive and sustainable flood defense systems (in conjunction with conventional flood defense systems).
The U.S. Army Corps of Engineers is leading a collaborative project to develop international guidelines to inform the planning, design, construction, and operation or NNBF projects. Participants in the international team come from several countries and organizations including the United Kingdom and the Netherlands and include representatives from government, academia, and the private sector. This paper will describe the emerging issues and likely content of the guidelines including aspects such as guiding principles, design rules for more novel forms of NNBF, spatial upscaling of flow-slowing measures across catchments and adaptive management of NNBF measures
Influence of the anisotropy of the material on the pore water pressures within the downstream shell of a rockfill dam in overtopping scenario
Get PDFThe compaction tasks developed during the construction of the shell of rockfill dams may crush the particles of the material close to each surface layer. If so, this can cause local variations in the permeability of the material and consequently an alteration of the hydraulic pattern of the seepage through the shell as well as the pore water pressures developed within it. This article summarizes the study of this effect through hydraulic numerical modelling developed by the FLOW-3D commercial code. Such study presents a discussion about the influence of the altered and unaltered zones of the layers on the general flow pattern, particularly in the downstream water level depths, hydraulic gradients and pore water pressures. The tests have been set up with a non-laminar seepage equation using a parabolic relation between hydraulic gradient and seepage velocity. The numerical models simulate homogeneous rockfill formed by isotropic layers with different permeability, which result in an overall anisotropic dam body
iCOASST: using morphological modelling to guide decision-making at the coast
No full textThis presentation will summarise the outcomes of the most recent work undertaken as part of the dissemination phase of the iCOASST project (REF) including:
(1) An evaluation (using pilot site modelling work developed for the Suffolk coastline)of whether, by using outputs from the iCOASST reduced complexity models of coastal morphology as inputs to the State of the Nation flood risk models, an improved assessment of future flood risk (taking account of long-term coastal morphological change, including change resulting from sea level rise and management interventions) could be achieved; and
(2) the guidance document developed for coastal managers to help them better understand the value and use of morphological modelling in supporting decision making at the coast.
The pilot site modelling work delivers important knowledge for future coastal FRA and model sensitivity testing; the guidance provides a unique, one-stop shop for coastal managers in explaining key coastal processes, their drivers, and the basic principles underpinning morphological modelling. It also provides a simple decision support tool that facilitates an evaluation of model applicability for a range of site characteristics
Dredging for sustainable infrastructure
No full textWith growing environmental awareness and increasing climate pressures on low-lying deltas, modern-day society puts incredibly strong demands on the sustainability of water infrastructure projects. Classic approaches towards the design and implementation of such projects no longer suffice in satisfying these demands.
Recent approaches look beyond the scope of isolated dredging activities and embrace a wider context, by considering water infrastructure development projects as an opportunity to also add value to the (natural and socio-economic) system in order to achieve more sustainable projects.
In the past 10-15 years, the international dredging community has embraced this kind of thinking and the approach to dredging has been transformed. From mainly dealing with negative impacts, often at the end of the project design and the start of the construction phase, towards a much more proactive approach where water infrastructure projects are being considered as part of the natural and socio-economic system in which they are situated, and stakeholders are being engaged much earlier in the project development process to facilitate the search for opportunities to create added value.
This change in attitude has a huge influence on the initiation, planning and design, execution and maintenance of water infrastructure projects. Comprehensive guidance on how to bring this into practice has to date been lacking. With this book a wide range of professionals have attempted to collect and integrate their experiences and best practices, to deliver this state-of-the-art guidance book on Dredging for Sustainable Infrastructure.
Comprised of nine chapters, the book discusses the topics of integrating dredging into sustainable development, sustainability in project initiation, planning and design, assessment and management of sustainability, equipment and methods, dredged material management, models and tools, and monitoring and data
The effect of a stabilized stone drainage layer on ACB performance in open channel flow applications
Get PDFThis paper will document and discuss the results of full scale flume testing of a tapered ACB system utilizing a stabilized stone drainage layer (Shoretec EPEC) under both steady state and hydraulic jump induced flow conditions. Articulated Concrete Block revetment systems have documented performance improvement when a stone drainage layer is included under the blocks, which was initially discovered in the late 1990’s and has largely remained an unstudied area of ACB testing for the past 25 years. In 2010 testing of a tapered ACB system was conducted in which the length of the test section was increased from 12.2 m to 21.3 m with a 10.2 cm thick stone drainage layer resulting in no apparent issues with the movement of the drainage layer. In 2013 more flume testing was conducted on a tapered ACB system in which the test section was increased from 21.3 m to 30.5 m and the stone drainage layer was increased from 10.2 cm to 15.2 cm. The results of this test showed significant ACB block movement at the 0.91, 1.22 and 1.62 m OT depths, in some instances exceeding 6.35 cm. In 2017 a 27.4 m test flume was constructed for a tapered ACB system (Shoretec EPEC) utilizing 15.2 cm of stone as a drainage layer with a 3-dimensional load platform added for stone stabilization. The results of this test run show that at 1.62 m of OT depth ACB block movement was kept to under 16 mm in the vertical and hydraulic jump stability was attained up to the maximum discharge flow of 2.579 m3/s/m on a 2:1 slope. Using the new design data, graphs will be presented showing the new range of hydraulic conditions now suitable for ACB tapered revetment systems with a stabilized stone drainage layer. In addition, design criteria necessary for the successful deployment of the 3-dimensional transfer platform system will be presented
Two large-scale test channels for overtopping and earthquake-flood compounded disasters
Get PDFExtreme flooding is mainly to the result of climate change, but sometimes it is brought on levee breaches and a subsequent flood disaster. Most levee breaches are the result of overtopping. Furthermore, river levees are also sometimes damaged by compound disasters following an earthquake, flood, or tsunami. With this in mind, it is necessary to develop comprehensive reinforcement technologies for river levees against overflow, infiltrations, and earthquakes. In the present study, we introduced two types of large-scale test facilities: one was a large-scale open channel to examine the resistance of model levees against overtopping and infiltration. The other was a channel to evaluate compound disasters of earthquakes and floods or tsunamis. The former channel was 20 m long, 1.0 m wide, and 1.8 m high and used to evaluate the erosion process and stability of river levees with various reinforcements against overtopping and infiltration. The levee height was set at 1 m. The latter channel was used to conduct a model experiment for compound disasters due to an earthquake, flood, and/or tsunami using a new channel that was 33 m long, 0.60 m wide, and 1.0 m high. In this paper, we introduce the examples of these large-scale model experiments using two channels. Furthermore, we demonstrate a new type of levee in which laminar drainage reinforcement (LDR) is laid along the back slope of the levee using geogrid layers. The experiment’s results suggest that LDR levees have a high resistance against overtopping and earthquakes
Flood resilience: consolidating knowledge between and within critical infrastructure sectors
No full textFlood resilience has been rising up the political, economic and social agendas. Taking an integrated systems approach, using the right design guidance and tools and ensuring that education is in place for all stakeholders are three themes which are intrinsically linked to delivering flood resilience. This paper reviews these themes across the academic research, policy landscape and practitioner approaches, drawing conclusions on the way forward to increase our societies resilience to floods. The term ‘flood resilience’ is being increasingly used, however, it remains to be clearly defined and implemented. The UK, USA and Australia are leading the way in considering what flood resilience really means, but our review has found few examples of action underpinned by an understanding of systems and complexity. This review investigates how performance objectives & indicators are currently interpreted in guidance documents. It provides an in-depth exploration of the methods, that although developed through European and US expertise, can be used for worldwide application. Our analysis highlights that resilience is often embedded in engineering education and frequently linked to risk. This may however, mask the importance of resilience and where it differs from risk. With £2.6 billion to be spent in the UK over the next 6 years on strengthening the country’s flood and coastal defences, this is the opportunity to rethink resilience from a systems approach, and embed that learning into education and professional development of engineers. Our conclusions indicate how consolidating flood resilience knowledge between and within critical infrastructure sectors is the way forward to deliver flood resilience engineering
Comparing soil erodibility predictions against the fundamental understanding of erosion
Get PDFIn breaching of levees, sediment erosion is induced by high flow velocities. Due to the often continuously accelerating flow, no equilibrium transport conditions are reached. The erosion rate is often described by the erosion equation which linearly relates the erosion rate to the excess shear stress by means of a soil erodibility coefficient. The soil erodibility is thereby often determined by means of the JET test. In the field of Dredging Engineering the study of the behaviour of sand under high flow velocities has also been an area of interest. At Delft University, the department of Dredging Engineering has performed several experiments on the behaviour of non-cohesive material when subjected to high flow velocities. It was noted that the initial porosity, and permeability of the material are important parameters to account for in the erosion process. This corresponds with observations that soil erodibility is sensitive to variations in material texture, compaction moisture content and compaction energy. It was furthermore noted that soil no longer erodes due to the pick-up of individual particles but fails as entire layers when subjected to high flow velocities. For shear failure to occur in non-cohesive soils the soil needs to dilate. The associated increase in pore volume causes an inflow of water into the soil. Based on the fundamental mass and momentum balance equations that describe the process of dilation of a bed when subjected to shear, a new process based erosion equation has been derived, which when validated against erosion measurements from the dredging industry shows promising results. This paper compares the prediction of soil erodibility by means of a JET test to the outcomes of the process based erosion equation. The paper highlights important differences and attempts are made to explain these