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Coastal erosion and king tides -

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Coastal erosion and king tides

Coastal erosion is a significant problem in Australia, as with many other nations, and it's set to
get worse. Reinhard Flick is studying the problem at the Scripps Institution of Oceanography in
California. But he's also an expert on king tides. He says they can be predicted well into the
future, which is pretty useful to know if you live on the coast.

Transcript

Robyn Williams: We're actually sitting on the beach in Southern California looking at the Pacific
Ocean on a very flat beach, very pleasant, good running beach. Very good beach indeed right now.

Reinhard Flick: Bit over a mile long.

Robyn Williams: Have you done that?

Reinhard Flick: Oh absolutely, when I was a young man I ran here regularly, couple of miles, down
and back.

Robyn Williams: Have you noticed any rise or fall of the ocean and the erosion of this beach?

Reinhard Flick: The California coast, especially in Southern California, is retreating. Perhaps up
to a foot or two per year. Most of that can be attributed to lack of sand. Now there are other
places, the Los Angeles area, the Santa Monica bay area and these beaches are familiar to everybody
that watches Baywatch, right, so the most popular TV show in the world. The Baywatch, beaches have
been artificially enhanced and widened and stabilised.

Robyn Williams: Just like the actors.

Reinhard Flick: Just like the actors may have been enhanced and stabilised. That's right. I hadn't
thought of it that way, but there is a parallel there. There's two ways that the beaches have been
widened and stabilised, first of all by placement of hundreds of thousands, some places millions of
cubic yards of sand over the last 50 years, and the construction of jetties and breakwaters like
the Marine del Rey breakwaters in Santa Monica, these engineering structures that have inhibited
the movement and therefore the rate of loss of sand.

Robyn Williams: Are these effects very costly? Billions, trillions?

Reinhard Flick: Well I don't remember the number that ah is attributable to coastal tourism, but
it's the largest, the single largest coastal dependent activity in California. I mean it's larger
than shipping, larger than the military, larger than ah manufacturing. It's very important
economically to California. So up there in the billions, easily in the billions.

Robyn Williams: What about the figures of maintenance that you've worked out yourself of the cost
per year?

Reinhard Flick: Well as far as sea level rise is concerned, this was a little surprising to me. But
if we assume a 50 cm rise in sea level over the next 100 years, of course the actual amount may be
larger, might be smaller, but 50 cm over the next 100 years seems to be a plausible mid range,
calculations of how much sand it would take to maintain the beach with in Southern California
ranges between round $1.5 to $2.3 or $3 billion over 100 years.

Robyn Williams: That doesn't sound much at all.

Reinhard Flick: No, well I guess it's $15 million to $30 million a year, say. That's a lot of money
for me, maybe not for you. But in terms of the budget of California, the value of the beaches, it
really isn't that much money.

Robyn Williams: Which would imply that it's affordable?

Reinhard Flick: Well I think it's affordable. I think it's more than affordable, I think it's
actually encouraging. I mean let's face it, when you say California, the first thing people thing
about are the beaches, right? So in view of the value both culturally and historically and
recreationally in tourism, I think it's actually a very small amount of money.

Robyn Williams: When you tell your colleagues about that, are they pleased or are they sceptical?

Reinhard Flick: I think people were surprised. I mean everybody I mention this number, these
conclusions to, except for folks I recently talked to, some engineers I talked to on the east coast
in the last few weeks, have come to similar conclusions about east coast beaches, especially in
Florida for example, that even to a greater extent than California depends on their beaches for
their economic livelihood. I mean let's face it, what else is there in Florida? At least in
California we have a more diversified economy. It really is much more heavily dependent on coastal
tourism than even California is. And therefore these same kinds of considerations are very
important for Florida, as they are for some countries including Australia.

Robyn Williams: Of course, the first thing that we think of in Australia is very high value real
estate, which you have here of course in La Jolla, California, especially. Are you taking that into
account, peoples' beach houses getting swept away?

Reinhard Flick: No, no, absolutely not. That's not part of this equation at all. And I would add
the very important thing that a lot of people overlook when they think of coastal property adjacent
to the beach that's in danger of being swept away from storms, is they think of the private
property, the private development, in many cases inappropriately sited private development. But I
have to point out that it's not just private homes, it's a lot of public facilities and public
infrastructure, I mean you just look at the building my office is in. It's protected by a seawall.
The entire frontage of Scripps Institution of Oceanography from one end to the other has a seawall.
It's very old, it's 50 or 60 years old.

Robyn Williams: It's quite short too.

Reinhard Flick: Well it's quite low because the sand level is pretty high, but ah when the sandy
road's 5 or 6 or 8 feet, you know that can be 12 or 14 feet high. And it's not just places like
Scripps, there are highways, there are railroads, there are piers, there are street ends, there are
lifeguard towers, there are restaurants, clubs, you name it. There's just a myriad of public and
publically accessible places, not to mention the military up here at Camp Pendleton, famous place
because a lot of their ?? in Afghanistan troops or marines are from Camp Pendleton. The Coronado
North Island Naval Air Station, the seal team training facility down there, all of these public
facilities are as valuable, if not more valuable, and as susceptible to damage from storms and
increasing damage as sea level rises, as any of the expensive private residences that you
mentioned.

Robyn Williams: Reinhard Flick at the Scripps Institution of Oceanography in La Jolla, California.

And so, retiring to his lab, virtually on the beach, he shows me figures for which he's famous,
working out when the king tides and the lowest tides occur, so that we can plan for big floods.

Reinhard Flick: Well of course a lot was known about tides since the 1600s when Newton figured out
what caused the tides, you know the motion of the earth, the sun and the moon. What was not so well
appreciated were some of the regular changes in tide range and especially the timing and occurrence
of the peak high tides, were not well understood until I and another researcher started to actually
look at the patterns in the early 1980s following the 1982/83 El Nino storms. During that time,
especially in January 1983, that happened to be the highest peak tides of about a four and a half
year cycle, the high tides on this coast occur in the summer and in the winter, and of course
occasionally during the winter high tides we have storms that coincide with the high tides. So
storms coinciding with high tides, that's when most of the beach erosion, that's when most of the
coastal flooding and the coastal structural damages occur. So describing the occurrence of peak
high tides, because they're so predictable, in principle you can predict tides hundreds of years
into the future, based on that we can make calendars that can give people windows for when the peak
high tides will be large, and therefore be able to anticipate when it's most likely that storms
will be able to do damages to the coast. So that's a very useful thing.

Robyn Williams: Why is there a difference between the two high tides during the day and indeed the
two low tides? Why aren't they the same?

Reinhard Flick: That has to do with the tilt of the earth and the tilt of the orbit of the moon.

Robyn Williams: And if you do have a storm coming and you're worried about the high tide, I suppose
it's useful to know which time the highest tide happens?

Reinhard Flick: Right, this is another thing that we've discovered and we're able to explain as a
coincidence, the relative motions of the earth to the sun and the moon. And one of the interesting
things about Southern California is that the highest tides of the day occur in usually early
morning in the winter time and in early evening or late afternoon in the summer time. And so if
there are storms that occur in the winter, it's in the early morning that we have to be alert to
this, because it's during this period of peak tide that those storms can do the most damage. And
those are early in the morning often in the winter time.

Robyn Williams: So you need to have good notice?

Reinhard Flick: Yes, you have to have good notice. And if the first time you hear about a pending
storm coming to the coast is on the 11 o'clock news at night before you go to bed, well then you
have a very short time to prepare and you have to sandbag or board up your windows or whatever at
night. And that's pretty inconvenient. So that's that's the value of having these ah peak tide
predictions far enough in the future, at least for a winter at a time, so that property owners and
coastal managers can anticipate when these windows of high tide will occur.

Robyn Williams: What big difference does an El Nino make?

Reinhard Flick: An El Nino, besides bringing more storms to the coast of Southern California also
tends to raise the sea level by up to 10 or 15 cms for a year or sometimes a year or two at a time.
And the past century's mean sea level rise was only about 20 cms, and so 10 cms is essentially 50
years worth of mean sea level rise. So during these very large El Ninos of which we've seen two or
three in the past century, we can have significant fractions of century's worth of sea level rise
all at once for a year or two.

Robyn Williams: You talk about your office being surrounded by a low seawall, now that's the sort
of thing that you need to protect an area, not least around Australia where most of our cities are.
What is the penalty of building a seawall for the beach?

Reinhard Flick: Well of course the seawall is built for the purpose of protecting development
behind the beach, so nobody says that it's built to protect the beach, it's not done for that. But
one of the negative consequences of seawalls which keep the back beach from moving or the cliff or
dune from retreating, if the shoreline retreats and nothing is done to maintain the beach with,
then the beach between the shoreline and the seawall will over time narrow and eventually
disappear. So that's the penalty.

Robyn Williams: So you build a seawall to protect your property and the beach disappears?

Reinhard Flick: Well if the shoreline retreats, so you have to have shoreline retreat, either
because of sea level rise or because of insufficient sand supply. But the answer for this is to
bring sand to the beach, to nourish the beach for modest rates of beach erosion, modest rates of
sea level rise. As we've talked about, sand nourishment is an effective way over many decades and
even a century or so to maintain the beach with in the face of sea level rise, even with seawalls.

Robyn Williams: The subtleties of saving your shoreline. Reinhard Flick does research on coastal
erosion at the Scripps Institution of Oceanography in La Jolla, California.