Science and technology
working with nature- civil and hydraulic engineering to aspects of real world problems in water and at the waterfront - within coastal environments
In an earlier piece, Civil Engineering on our Seashore, I have presented and broadly outlined the Coastal Engineering Envelope where several civil engineering measures were shown – that cater to the needs for protecting and developing the seashore. A brief of some 24 different kinds of coastal and port hydraulic structures were listed there. On this piece let us attempt to learn about the Storm Surge Barrier – but in a wider context of Flood Barrier Systems. The barriers as a way of managing water and floods – have two basic engineering components. The first is the dike on low lands, connected to the second component – the gated stream/river/estuary/waterway closure structures. The works represent a system that accounts for many engineering challenges – hydraulic, structural, geotechnical, and risk assessment – as well as impacts on the ambient environment defined by local Fluid, Solid and Life systems (see e.g. Environmental Controls and Functions of a River). In the back drop of Warming Climate with consequent Sea Level Rise, flood barrier systems are becoming increasingly relevant – as one of the management Strategies to cope with the threatening rising sea, and increasingly frequent and intense storm surge.
This piece is built upon materials gleaned from several sources and websites. Unless specified otherwise, they include the following. On river floods: Hydraulic Design of Flood Control Channels, USACE EM 1110-2-1601; Hydrologic Frequency Analysis, USACE EM 1110-2-1415; and Design and Construction of Levees, USACE EM 1110-2-1913. On coastal flood/storm surge: Storm Surge Analysis and Design Water Level Determinations, USACE EM 1110-2-1412; Hurricane and Storm Damage Risk Reduction System Design Guidelines, USACE; and TUDelft (VSSD) Breakwater and Closure Dams (2008, 2nd ed).
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Before jumping on to discussing the flood barrier systems – perhaps it would be instructive to begin by introducing the Water Barrier concept in a broader context. Because all barriers under this generic term, and in the capacities of a hydraulic structure – have one common purpose – that is to protect an area from the onslaught of water actions. These protections can simply be sorted out against the actions of:
Some common preventative soft and hard engineering measures usually installed for protections against such actions are listed in the Civil Engineering on our Seashore. Perhaps it is helpful to group them pertaining to specific water actions – together with an outline of common assessment routines.
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Flood Barrier Hydraulics
It is necessary to comprehend some key hydraulic technical issues – that are important in aspects of planning, designing, construction, and functions. In all these aspects, different methods and practices are implemented in ways – how a barrier handles the potential and kinetic energies – in eliminating, reducing or modulating their power.
Let us attempt to see them. In barriers installed to prevent flooding due to inundation and runup – potential energy is gradually elevated as the hydraulic head difference increases between the two sides of a barrier. One knows too well that the forces caused by the difference – exerted on an earthen dike, a vertical monolithic wall, or a gated barrier structure – are what cause failures (see Civil Engineering on our Seashore). The threats to their stability and integrity take different dimensions and can be translated into:
Highlights of Some Major Storm Surge Barriers
In the world of modern flood barrier engineering, the first one to occupy the history book is the 32 km long Afsluitdijk closure dam in the Netherlands completed in 1932. This dam separates the shallow IJsselmeer Lake from Wadden Sea. The primary purpose of this dam was to reclaim land from the lake. Starting from this great feat of hydraulic engineering, let me highlight some major storm surge barriers completed around the world.
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MOSE Project Venice, Italy
It has been a great pleasure writing this piece. Let me finish it with a little Koan:
Why let it wither away, some water-of-life on the plant would have worked to let it stand upright and unfold the fragrance of flower.
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- by Dr. Dilip K. Barua, 26 January 2020