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
This piece is a continuation of the Sea Level Rise – the Science post on the Nature page. Let us attempt to see in this piece how different thoughts are taking shape to face the reality of the consequences of sea level rise (SLR). The consequences are expected across the board – in both biotic and abiotic systems. But to limit this blog to a manageable level, I will try to focus – in an engineering sense – on some aspects of human livelihood in frontal coastal areas – some of the problems and the potential ways to adapt to the consequences of SLR.
Before doing that let us revisit one more time to point out that all familiar lives and plants have a narrow threshold of environmental and climatic factors, within which they can function and survive. This is in contrast to many microorganisms like Tardigrades, which can function and survive within a wide variation of factors. Therefore adaptation can be very painful, even fatal when stresses exceed the thresholds quickly – in time-scales shorter than the natural adaptation time.
What is stress? Global warming and SLR literature use this term quite often. Stress is part of the universal cause-effect, force-response, action-reaction, stress-consequence duo. In simple terms and in context of this piece, global warming is the stress with SLR as the consequence – in turn SLR is the stress with the consequences on human livelihood in the coastal zone.
Again, as I have mentioned in the previous piece, the topic is very popular and literature are plentiful with discussions and opinions. The main resources consulted for this piece are the adaptation and mitigation chapters of the reports worked on by: UN entity IPCC (Intergovernmental Panel on Climate Change), US NOAA (National Oceanic and Atmospheric Administration), and USACE (United States Army Corps of Engineers).
Before going further, it will be helpful to clarify the general meanings of some of the commonly used terms – these terms are used in contexts of system responses and reactions – susceptibility, prevention, the ability to adjust to changes, and the ability to cope with repeated disruptions. The first is vulnerability – the susceptibility and inability of a system to cope with adverse consequences or impacts. One can simply cite an example that human habitation, coastal and port infrastructure in low lying areas are more vulnerable to SLR than those lying in elevated areas – and so are the developing societies than the developed ones.
The second is known as mitigation – the process of reducing the stresses to limit their impacts or consequences. We have seen in the NATURE page that there could be some 8 factors responsible for SLR. But scientists have identified that the present accelerated SLR is due to the continuing global warming caused by increased concentration of greenhouse gases. This anthropogenic factor is in human hands to control; therefore reducing greenhouse gases is one of the mitigation measures.
The third is adaptation – the process of adjusting to the consequences of expected or imposed stresses, in order to either lessen or avoid harm, or to exploit beneficial opportunities. This is the primary topic of this piece – how humans could adjust to the consequences of SLR. The fourth is closely related to adaptation and is known as resilience – the ability to cope with repeated disruptions. It is not difficult to understand that adaptation process can become meaningless without resilience.
Also to note that a successful mitigation can only work with some sort of adaptation – for example, adaptation by innovating new technologies to control and limit greenhouse gas emission. However, one may often require to compromise or make trade-offs between mitigation and adaptation processes to chalk out an acceptable solution.
I have included an image (credit: anon) of human habitation and township developed on a low lying barrier island. Similar developments occur in most coastal countries – some are due to the pressure of population increase, while others are due to the lack of foresight and understanding by regulating authorities. Such an image is important to look at, to reflect on and to think about human vulnerability, and the processes of mitigation, adaptation and resilience to the consequences of SLR.
Before going further, some aspects of climate change that exacerbate the SLR effects need to be highlighted. The first is the enhanced wave activity associated with SLR. We all have seen the changing nature of waves sitting on a shoreline during an unchanging weather condition – less wave activity at low tide and enhanced waves as tide rises. Why does that happen? One reason is the depth-limited filtering of wave actions – for a certain depth only waves smaller than about 4/5th of water depth could pass on to the shore without breaking. Therefore, as the water level rises with SLR, the numbers of waves propagating on to the shore increase.
The second is the enhanced storminess caused by global warming. All the climate change studies indicate the likelihood of increase in storminess both in intensity and frequency – and perhaps we are witnessing symptoms of that already. High wind storms are accompanied by high storm surges and waves together with torrential rainfall and terrestrial flooding.
What are the consequences of SLR? The consequences are many – some may not even be obvious at the present stage of understanding. They range from transgression of sea into the land by erosion, inundation and backwater effect, to salt-water intrusion, to increased forces on and overtopping of coastal waterfront structures.
If the 2.0 meter SLR really (?) happens by the end of the 21st century, then it is impossible for one not to get scared. I have included a question mark to the 2.0 meter SLR because of the high level of uncertainty in the predictions by different organizations (see the Sea Level Rise – the Science blog on the NATURE page). For such a scenario, the effective SLR is likely to be no less than 10.0 meter affecting some 0.5 billion coastal population. The effective SLR is an indication of the range of consequences that a mean SLR would usher in.
Let me try to provide a brief outline of the consequences. First, one should understand that the transgression of sea into the land is not like the invasion by a carpet of water gradually encroaching and inundating the land. It is rather the incremental incidences of high-tide-flooding combined with high wave activity. The result is the gradual net loss of land into the sea through erosion and scour, sediment-morphological readjustments and subsequent submergence.
What adaptation to SLR really means? Let us think of coastal population first. Survival instinct will lead people to abandon what they have, salvage what they can, and retreat and relocate themselves somewhere not affected by SLR. Although some may venture to live with water around if technological innovations come up with proven and viable measures. There are many traditional human habitations in seasonally flooded low lands, and also examples of boathouses around the world. Therefore, people’s lives are not so much at stake in direct terms; it is rather the monetary and emotional losses they would incur – losses of land, home and all of their valuable assets and memories. This adaptation process will not be equally felt by all the affected people. Rich people and perhaps many in developed societies are likely to cope with the problem better than the others.
Perhaps the crux of the problem will be with civil infrastructure. One can identify them as four major types – coastal defense structures (e.g. dikes, seawalls, revetments and groins), port and harbor infrastructure (e.g. breakwaters, quays, wharves and jetties, and dolphins), city and county utility infrastructure (e.g. drainage outlets, bridges and culverts and coastal roads), and homesteads. The problem infrastructure will also include various nearshore and offshore in-water oil platforms and facilities. There is no denying that all these structures standing at the waterfront and in-water will become vulnerable to the water forces high in magnitude and frequency – with enhanced slamming and increased incidences of overtopping and scour. City drainage and disposal outlets will be additionally affected by backwater effects. These stresses are likely to gradually undermine the functionality and failure of structures.
Some other aspects of the problem lie with the intrusion of sea saline water into estuaries, inlets and aquifers. Coastal manufacturing and energy facilities requiring freshwater cooling will require adapting to the SLR consequences. The problem will also be faced with the increased corrosion of structural members.
What to do with this huge problem of the existing civil infrastructure? What does adaptation mean for such a problem? One may think of renovation and reinforcement, but the likelihood of success of such an adaptive approach may be highly remote. How do the problems translate to the local and state’s economy? What about abandoning them to form submersed reef – declaring them as Water Park or sanctuary? - leaving many as remnants for posterity like the lost city of Plato’s (Greek Philosopher, 423 – 347 BCE) Atlantis? There are no easy answers to any of these questions; but there is no doubt that stakes are very high. We can only hope that such scenarios would not happen.
What is important and is being initiated across the board is the formulation of mitigation and adaptation strategies and policies. Such decision making processes rely on the paradigm of risk minimization – but can only be meaningful if uncertainties associated with SLR predictions are also minimized. One important area of work where urgent attention is being paid is in the process of updating and redefining the standards, criteria and regulations required for robust planning and design of new coastal civil infrastructure. However, because of uncertainties in SLR predictions even this process becomes cumbersome. Placing concrete and steel to build anywhere is easy, what is not easy is envisioning the implications and the future.
Well, some thoughts in a nutshell, shall we say? But mitigation of and adaptation to a complex phenomenon like global warming, climate change and SLR must be understood as an evolving process – perfection will only likely to occur as things move forward. And one should not forget that the SLR problems as complex and intimidating as they are, are slow in human terms – therefore the adaptation processes should be conceived in generational terms, but all indications suggest that the thinking and processes must start without delay. Fortunately all members of the public are rightly concerned, and but are all pleased whether things are rolling in the right direction.
Here is an anecdote to ponder:
The disciple said, “Sir, adaptation is a very strong word perhaps more than what we think it is.”
The master replied, “Yes, it does have a deeper meaning. One is in the transformation of the personalities undergoing the adaptation processes. It is a slow and sequential process ensuring the fluidity of Nature and society and evolution. If one thinks about the modern age of information, travel and immigration, the process is becoming much more encompassing – perhaps more than we are aware of. But while slow adaptation is part of the natural process, the necessity of quick adaptation can be very painful and costly.”
. . . . .
- by Dr. Dilip K. Barua, 29 September 2016