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The beach that didn't erode when it should have

September 3, 2012 - Harry Eagar
A tale of three coastlines

Two of Maui's coastal areas have been in the news during the last couple of weeks, but just as interesting is a third one that has not been, but was supposed to be.

The ones in the news are Launiupoko, where Honoapiilani Highway is falling into the ocean, and the Kahului sewage treatment plant, where an 1,100-foot seawall is proposed to keep buildings from being washed out.

Not in the news is the long stretch of beach along North Kihei Road. Old-timers may recall that some 18 to 20 years ago, it was predicted that erosion would reach the road within five years. It didn't.

What happened? Cars struck two hawksbill turtles that were crawling across the highway looking for a place to nest. In alarm about wildlife, snow fences were put up to halt the turtles before they got to the road.

This apparently also had the effect of changing the dune geometry enough to retard the alongshore erosion. Unfortunately, something as cheap and benign as a snow fence is probably not going to do the job that seawalls do.

And benign is relative. The fences have prevented any more endangered turtles from being run over and killed, but although motorists killed a large fraction of the hawksbill that like that stretch of beach for nesting, they didn't get them all.

Since the fences went up, several nests have been discovered, but, for lack of access to a place they'd like, in the high dune close to the waves. Not one of these nests has resulted in developed eggs.

Turtle watchers suspect that the locations are too dry and salty. Mother knows best. Farther inland is better.

I don't know what could be done about this. Maybe dig up nests and relocate them, and then help the hatchlings to the water.

Maybe water the nests in place.

Launiupoko is an example of the rule that if you defer maintenance long enough, a minor problem will become a crisis.

That the shoreline is retreating there has been obvious for a long time. During Hurricane Iniki, waves were hurling softball-size rocks across the road like cannonballs.

As long as Pioneer Mill was farming that area, it was unlikely anything would be done to move the road inland. When Pioneer left, a golden chance to pick up the land cheap and begin realigning the road was missed.

Since then, slow progress has been made. Not fast enough to prevent the state DOT from armoring the shoreline.

At one point – I believe it was during Linda Lingle's mayoralty – the planning department decided it would no longer support any further armoring of Maui's shores. It always causes trouble somewhere down the line.

That was good policy. But it's been forgotten.

Now the county itself is proposing to further harden the shoreline near the airport.

The alternatives were all expensive.

Moving the sewage treatment plant inland was expected to cost nearly half a billion dollars. Naturally, the council preferred to waterproof the plant.

Even that cost many tens of millions. The idea is that when a tsunami or hurricane threatens to swamp the plant, it will be shut down and buttoned up. The waves will wash over the plant, doing (it is hoped) little permanent damage to Kanaha Pond wildlife refuge as the partially treated sewage in open tanks is spread around.

If the electrical systems are waterproofed, the plant can be restarted within a day or so after the overflow. (The Japanese should have been so prudent at Fukushima, although to work this plan requires adequate warning, which the Japanese tsunami did not give.)

Not mentioned, that I can recall, during the discussions about waterproofing the plant was the coming need to armor the shoreline. 1,100 feet is a lot of seawall, bound to cause trouble downcurrent – which at that location is in either direction, because the current changes direction with the seasons.

 
 

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