Flowing the waves 09022018
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1) Accelerated climate change is impacting coasts through multiple interacting factors like changing weather patterns, wave energy spectra, and sea level rise. 2) A potentially significant threat is the increase in long wave energy, which is difficult to measure and analyze due to limitations in coastal monitoring instruments. 3) To better manage these climate change impacts, coastal resilience strategies need to take a holistic, system-wide approach focusing on the balanced interaction between incoming conditions and natural coastal dynamics, rather than traditional approaches like raising sea defenses.
![© Marco Pluijm, 09/02/2018
[photo credit Peter Chadwick, 2014]
Flowing the waves; managing the impact of
accelerated climate change
Marco Pluijm M.Sc.
Innovator and Seasoned Professional
…. in an era where “wider becomes better than higher”
The combined effect of accelerated climate change on a coast is characterised by
multiple parameters, interacting with one another, leading to a great variety in
phenomena and intensities.
Still, often when reference is made to climate change, sea level rise is (usually)
considered as the most important and compelling factor. With often hardly any to no
attention for other conditions, such as changing weather patterns, duration and
intensity, wave energy spectra, directional spreading, etcetera
Storm surge and wave set up are depending on the changing weather as well as sea
level rise as such. Another major factor is temperature and the effect that imposes on
extreme weather conditions.
A potential silent killer within this bundle, is the (often significant) increase in (bound)
long wave energy. A phenomenon often hard to assess due to its nature and the way
of recording and monitoring. Most instruments were (and still are) not suitable to
register this phenomenon properly. Reason why reliable historic time series are often
hard to find and even when recorded, adequate data analyses are still essential to
filter out what it is one is looking for.
One of the reasons why such hidden increase can be seen as a silent killer. Showing
its impact for instance with an unexpected increase in port operations downtime.](https://image.slidesharecdn.com/flowingthewaves09022018-180209114549/85/Flowing-the-waves-09022018-1-320.jpg)
Flowing the waves 09022018
- 1. © Marco Pluijm, 09/02/2018 [photo credit Peter Chadwick, 2014] Flowing the waves; managing the impact of accelerated climate change Marco Pluijm M.Sc. Innovator and Seasoned Professional …. in an era where “wider becomes better than higher” The combined effect of accelerated climate change on a coast is characterised by multiple parameters, interacting with one another, leading to a great variety in phenomena and intensities. Still, often when reference is made to climate change, sea level rise is (usually) considered as the most important and compelling factor. With often hardly any to no attention for other conditions, such as changing weather patterns, duration and intensity, wave energy spectra, directional spreading, etcetera Storm surge and wave set up are depending on the changing weather as well as sea level rise as such. Another major factor is temperature and the effect that imposes on extreme weather conditions. A potential silent killer within this bundle, is the (often significant) increase in (bound) long wave energy. A phenomenon often hard to assess due to its nature and the way of recording and monitoring. Most instruments were (and still are) not suitable to register this phenomenon properly. Reason why reliable historic time series are often hard to find and even when recorded, adequate data analyses are still essential to filter out what it is one is looking for. One of the reasons why such hidden increase can be seen as a silent killer. Showing its impact for instance with an unexpected increase in port operations downtime.
- 2. © Marco Pluijm, 09/02/2018 Once that happens, adequate response strategies will often be hard to find. In absence of such an operational barometer, considerable time may pass by before all of a sudden a long wave induced strong increase in coastal erosion manifests itself, without any warning. A cry for additional nourishment is then often what springs to mind as adequate response strategy. However, given the nature of the underlying physics and so the problem, something that even might have an adverse effect. Still, with levels rising and intensities growing, there appears to be some sort of natural tendency to stick to the traditional approach, including raising of sea defences and dunes accordingly. Question is if this still makes sense once the overall nature of the entire load package diverts from what was seen as the norm so far. For instance, a substantial increase in the percentage long wave energy relative to what was a predominantly short wave spectrum, requires a very much different approach towards what’s often referred to as the “active zone”. Part of the foreshore traditionally seen as the area from the breakerline upwards. Which area now will expand dramatically into deeper water once the contribution of long waves becomes more significant, taking along the type of energy dissipation mechanism and its effectiveness. One crucial element in the equation is the actual condition (or “health”) of that foreshore, in particular with regard to its natural phenomena such as sand banks and other features such as ridges, sand waves, etcetera. While in terms of accelerated climate change induced ambient conditions and load package, focus needs to be on the combination of all factors and not “just” sea level rise. And how their impact can be managed and reduced in the sense that their combined energy is broken up and spread more evenly, relative to the traditional response with regard to raising dunes and dikes and/or more (frequent) nourishment sand. In case sand banks and other morphological features are no longer present or in bad shape, they can be restored or even rebuilt. According or adjusted to the now governing ambient conditions. Which may mean that in order to (re)create such natural system across and along the affected coast, some (periodic) sediment support may be needed. Which is very much different from the traditional foreshore nourishment. Traditional foreshore nourishment manifests itself as a human intervention, and actually deliberate obstruction, meant to act like a wear layer, compensating for a pre-defined amount of erosion and related period of time. No cases are known of such an intervention as stimulus nor active contribution to the restoration of natural coastal dynamics as such. While with ambient conditions changing as described and related subsequent increase of a larger part of the foreshore, utilisation, managing and/or restoration of the required dynamics is the goal to achieve. With so far often little attention for this extended part of the foreshore following the traditional approach, actual knowledge and experience levels with regard to processes, key parameters and planning tools, are usually (relative) limited.
- 3. © Marco Pluijm, 09/02/2018 Major part of these gaps can be filled in with experience and knowledge from abroad, around the globe, thanks to the fact that the underlaying physics basically are the same. In this respect much can be learned from the behaviour of sandy coasts, ridges and barrier islands along the US coast and Australia. Translating this approach to for instance the Dutch situation implies foreshore analyses, restoration and improved utilisation and effectiveness on the basis of thus combined knowledge and experience. All together the outcome focuses on a balanced interaction between incoming ambient conditions and adequate, predefined coastal dynamics. Predefined in the sense that an increase in ambient conditions (sea level rise, storm surge, set-up, wave duration and intensity, long wave energy) will be reduced and broken up across and along the active part of the foreshore by means of extended energy dissipation and redistribution via increased bottom friction, overwash and return flow. Extended dissipation and phased waterlevel reduction is achieved by means of sequential, shore parallel morphodynamic features, such as sand banks, ridges etc. Adequate interspacing takes care of a balanced return flow. Actually dividing the affected coast in hydro-morphological compartments or cells. All together providing a healthy base for natural recovery and resilience. All under the strict condition not to (re)create any subaerial entities such as offshore barrier islands etc. What just would shift issues to deeper water and make things worse. In case of incidental need for external support, (some) sediment feed might be considered under the strict condition that it is based on rebalancing dynamics, not volumes. All based on a holistic, system wide approach in an era where “wider is better than higher” is to become the slogan and eventually the new norm for reasons given in this post. Most of what’s written has been substantiated as part of the Resilient by Nature approach, creating opportunities for work in progress. Marco Pluijm February 9th , 2018