Excerpts of the Business Insider article by Aylin Woodward
Hawaii’s iconic Waikiki Beach could be engulfed by the ocean in 20 years — here’s the plan to save it
In May 2017, high tides engulfed parts of the iconic Waikiki beach, edging dangerously close to waterfront hotels. This kind of high-tide flooding, often called a king tide or sunny-day flood, occurs when ocean water surges to higher levels than coastal infrastructure was designed to accommodate. In that case, water levels rose 2.5 feet above average in Waikiki, drowning nearby roads and sidewalks.
According to a 2017 report (which was updated in September 2018), Hawaii’s state capital and Waikiki Beach – along with other coastal strips on Hawaii’s five islands – are expected to experience frequent flooding within 15 to 20 years.
“This flooding will threaten $5 billion of taxable real estate; flood nearly 30 miles of roadway; and impact pedestrians, commercial and recreation activities, tourism, transportation, and infrastructure,” Shellie Habel, lead author of the 2017 study, said in a release.
Now, Hawaii state lawmakers are taking steps to shore up the state’s beaches and coastal cities. A new bill that mandates a statewide shore protection program has passed both houses of Hawaii’s state legislature, and will soon makes its way to the governor’s desk for approval.
All well and good that they want to improve beach resilience. But, the claim that ” Hawaii’s iconic Waikiki Beach could be engulfed by the ocean in 20 years ” is totally bogus.
Here is why:
First, lets look at real world data (as opposed to model projections).
Source:
https://tidesandcurrents.noaa.gov/sltrends/sltrends_station.shtml?id=1612340
According to the official NOAA data, there is a 1.49mm per year sea level trend extending back to the year 1900.
According to elevation data via Google Earth the top of Waikiki Beach is about 8 feet above the mean sea level there.
8 feet = 2438.4 milimeters
…at a rise rate of 1.49mm/year based on the NOAA sea level rise rate we have:
2438.4 mm / 1.49 mm/year = 1636.5 years
In 20 years, sea level would have advanced only
1.49 mm/year x 20 years = 29.8 mm or 0.098 feet
Once again, reporters can’t do basic math, but they sure can exaggerate.
Next, let’s look at the 2017 Report they cited as “having passed peer review”, from the methodology section:
Modeling, using the best available data and methods, was conducted to determine the potential future exposure of each island to multiple coastal hazards as a result of sea level rise. Three chronic flooding hazards were modeled: passive “bathtub” flooding, annual high wave flooding, and coastal erosion. The footprints of these three hazards were combined to define the projected extent of chronic flooding due to sea level rise, called the sea level rise exposure area (SLR-XA). Not all hazards were modeled for each island due to limited historical information and geospatial data. Each of these hazards were modeled for four future sea level rise scenarios: 0.5 feet, 1.1 feet, 2.0 feet and 3.2 feet based on the upper end of the IPCC, Assessment Report 5, representative concentration pathway 8.5, or “business as usual” sea level rise scenario.
Even with 3.2 feet of projected sea level rise, the threat when viewed in terms of real-world data is many years away:
3.2 feet = 975.36mm 975.36mm/1.49 mm/yr = 654.6 years.
As anybody in the climate business knows, RCP8.5 is a ridiculous “worse than worst case” climate model that has no real-world counterpart. Only politicians and low information journalists give it any credence.
The follow of this entire thing is that they’d rather look at model data, than the real-world data. But then again, you can’t get grants for stuff that will happen 600 to 1000 years in the future, can you?
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50 Year mean used to be 1,99 now it is 1,30
https://tidesandcurrents.noaa.gov/sltrends/sltrends_station.shtml?id=1612340
Why listen to the alarm?
“In May 2017, high tides engulfed parts of the iconic Waikiki beach, edging dangerously close to waterfront hotels. This kind of high-tide flooding, often called a king tide or sunny-day flood, occurs when ocean water surges to higher levels than coastal infrastructure was designed to accommodate. In that case, water levels rose 2.5 feet above average in Waikiki, drowning nearby roads and sidewalks.”
Average what? High tide? Mean sea level? If the top of the beach is 8 ft above mean sea level, 2.5 feet isn’t going to flood anything.
High tide isn’t the only problem they face. Hawaii has the distinct pleasure of hosting hurricanes from time to time. With hurricanes come surges that can be as high as 40 feet plus waves. That is way higher than the 8 ft of the top of beach. Note that it CAN be that high, not that it will be that high.
From Wikipedia:
“Hurricane Iniki made landfall on the south-central portion of Kauaʻi island, bringing its dangerous inner core to the entire island.[1] Upon making landfall the hurricane produced storm tides of 4.5–6 feet (1.4–1.8 m), with some portions of the coastlines having high-water marks of up to 18 feet (5.5 m). In addition, strong waves of up to 35 feet (10.5 m) in height crashed along the southern coastline for several hours, causing a debris line of more than 800 feet (250 m) inland. Because it moved quickly through the island, there were no reports of significant rainfall.”
So whether or not they are motivated by climate change or overall vulnerability doesn’t matter. They probably do need a mitigation strategy. And for much more than just that beach.
Given media’s desire to push all things climate change, some of the motivation may be due to hurricanes as well as alarmism. If certainty is desired, you can probably look up the legislature’s discussion of the law. Doing something right for the wrong reason is still doing something right.
There was a study reported here a few years ago. It was looking at old paintings of sea fronts and harbours and comparing them with modern photographs. I recall one site was Valetta harbour – no change in ~200 years…..
If they want a really scary story about Waikiki/Honolulu why not use a flank collapse on the “big island”? That would wipe out every coastal settlement in the state and cause extensive damage all around the Pacific basin.
And it is certain to happen sooner or later. Such large volcanic piles as the Hawaiian islands are inherently
unstable. The whole northern side of Oahu for example is a single huge slide scar.
https://www.youtube.com/watch?v=uPIx0B9O8Us
https://www.researchgate.net/publication/233529887_Megatsunami_deposits_on_Kohala_volcano_Hawaii_from_flank_collapse_of_Mauna_Loa
This is all you need to know.
Hawaii’s state legislative makeup
Senate, 25 members; 24 of which are Demcos.
House, 51 members; 46 of which are Demcos.
Lets see now what is more of a threat to Hawaii ?
A. Water rising less than half a foot every 100 years .
B. Volcanoes that blow up to form and expand the islands constantly .
C. Democrats
D. Loonie tunes in North Korea .
Andy wrote: “According to elevation data via Google Earth the top of Waikiki Beach is about 8 feet above the mean sea level there.”
In case no one noticed above, staying above MEAN sea level for the next 1636 years in not good enough. In 1636 years, the top of the beach will be underwater 50% of the time at high tide. Ideally, the top of the beach needs to be above the highest tide 100% of the time, which means at the highest tide during the surge from the strongest winds and lowest pressures. If, as your article says, high tide in May 2017 came dangerously close to hotels and infrastructure, then NO margin of safety exists today. That problem is getting worse by about 1 inch every 15 years – or 1 inch/decade if you believe satellite altimetry. Did Honolulu really allow all of those hotels and infrastructure to be built 70 years ago with only a few inches of safety margin – a safety margin that has been consumed by sea level rise. That doesn’t make sense to me, but dumber things have happened. In Atlantic City, NJ, a few streets are routinely flooded by the highest tide every month. These streets are well inland and not exposed to waves. The problem may be caused more by settling than sea level rise.
Due to natural variability in sea level (say from shifting winds), the local tide gauge is incapable of distinguishing the difference between 1 inch/15 years and 1 inch/decade over the last few decades – even though the average rate of rise over the last century is far more accurate than this. However, you needed to take autocorrelation into account when calculating confidence intervals. Monthly tide gauge data is usually highly autocorrelated.