Coastal erosion in Hawai`i? It's sea level rise, silly.

Many Hawai`i beaches are eroding and it should be no surprise that the primary culprit is sea level rise.

Hawai`i researchers recently published a paper in the journal Global and Planetary Change that concluded that the main cause of coastal erosion in the Islands is rising ocean levels.

(Image: Maui beaches are eroding at an average of half a foot a year. Shown here is a coastal building on Maui, threatened by chronic coastal erosion. Credit: Zoe Norcross-Nuu.)

There are certainly other factors, like currents and the relative rise and subsidence of the islands themselves, but sea level’s the big one.

It means, in part, that people assuming those disappeared beaches will return cyclically to their previous size will wait in vain, and that the state’s decision-makers need to plan for continued coastal erosion.

“Shorelines find an equilibrium position that is a balance between sediment availability and rising ocean levels. On an individual beach with adequate sediment availability, beach processes may not reflect the impact of SLR. With this research, we confirm the importance of SLR as a primary driver of shoreline change on a regional to island-wide basis,” said Brad Romine, a coastal geologist with the University of Hawai`i Sea Grant College Program.

What he’s saying there is that if a beach still has a large natural dune system behind it—like, for instance, Polihale on Kaua`i—the sand will replenish the retreating shoreline and you’ll still have a beach. But of course, most of the state’s dune systems are long gone.

Sea level has been going up at nearly a tenth of an inch a year for most of the 1900s, but the level has increased recently to slightly more than a tenth of an inch a year—from 2 millimeters to 3 millimeters. That works out to sea level rise of three-quarters of an inch per decade accelerating to more than an inch.

Doesn’t seem like much, but at the current rate, a kid born today will see sea levels more than half a foot higher by retirement age. Imagine an additional seven or so inches on top of today’s highest tides, and the picture looks ominous for coastal roads, beach parks, coastal resorts, and sandy beach oceanfront homes.

That’s because each inch in sea level rise translates to several inches of coastal retreat. Maui beaches, of which 78 percent are eroding, have lost on average half a foot a year. Most O`ahu beaches are also eroding, but at a far lower rate, about an inch a year.

Some coastlines clearly get hurt more than others, and calculating the different coastal responses has been a major piece of Charles “Chip” Fletcher’s work.

“Improved understanding of the influence of SLR on historical shoreline trends will aid in forecasting beach changes with increasing SLR,” said Fletcher, Associate Dean and Professor of Geology and Geophysics at the University of Hawai`i School of Ocean and Earth Science and Technology.

Citation: B M Romine, C H Fletcher, M M Barbee, T R Anderson, L N Frazer (2013) Are beach erosion rates and sea-level rise related in Hawaiʻi? Global and Planetary Change, doi: 10.1016/j.gloplacha.2013.06.009

A press release on the project adds: “The research described in this paper was carried out by the University of Hawaiʻi Coastal Geology Group with the support of the State of Hawaiʻi; Counties of Kauaʻi, Oʻahu and Maui; U.S. Geological Survey; U.S. Army Corps of Engineers; NOAA; Hawaiʻi CZM; Hawaiʻi Sea Grant; and the Harold K.L. Castle Foundation.  This paper is funded in part by a grant/cooperative agreement from the National Oceanic and Atmospheric Administration, Project A/AS-1, which is sponsored by the University of Hawaiʻi Sea Grant College Program, SOEST.”

© Jan TenBruggencate 2013

Deep ocean canyons around Hawai`i are hot spots for species diversity

Often science simply confirms what you’d suspect. Example: Life is more interesting in a complicated landscape than a simple one.

(Image: Some of the canyons off Kane`ohe Bay. Credit: UH Mānoa.)

Case in point: You get more life and more kinds of life in the wrinkled landscape of Hawaiian undersea canyons than on the broad flats. 

University of Hawai`i marine researchers determined that biodiversity is significantly higher in the submarine canyons around Hawai`i than on the flats, largely because the canyons provide so many more types of habitat, but also because they concentrate nutrients.

The researchers reported in the journal Deep Sea Research Part II after 34 dives with the submersibles Pisces IV and V up and down the archipelago, from the main Hawaiian Islands to the Papahānaumokuākea Marine National Monument in the Northwestern Hawaiian Islands. 

Their dives took them to study points at multiple depths, the deepest of them near a mile down. The principal researcher was UH oceanography professor Craig Smith.

In the canyons, they found both complexity of habit an increased biodiversity. 

 “Submarine canyons encompass myriad habitat types. This heterogeneity at the landscape-scale helps to enhance local biodiversity in canyon seafloor sediments,” said lead author Fabio C. De Leo, a doctoral graduate from UH Mānoa’s department of oceanography. Species diversity is considerably higher in canyons, he said.

In canyons, many things are happening. There are diverse physical habitats. Ocean currents are channeled. Sinking particles are captured. Too, a lot of the organic material washed off the islands ends up settling in canyons, where they decompose and add nutrients to a portion of the ocean normally limited in food availability. 

“When there’s more food, there’s more life,” De Leo said.

Says the University press release: “This series of dives was conducted on the Pisces IV and Pisces V manned submersibles operated by the Hawai‘i Undersea Research Laboratory (HURL).  The research was conducted in partnership with Hawai‘i Pacific University and the New Zealand National Institute of Water and Atmospheric Research.”

The paper’s abstract is here.

Here is the University of Hawai`i press release.

Here is the citation: Fabio C. De Leo, E.W. Vetter, C. R. Smith, A. R. Ashley, and M. McGranaghan.  Spatial scale-dependent habitat heterogeneity influences submarine canyon macrofaunal abundance and diversity off the Main and Northwest Hawaiian Islands.  Deep Sea Research Part II: Topical Studies in Oceanography.  11 July 2013.

© Jan TenBruggencate 2013

Hawaii Energy Storage 9: A wrapup message: Follow the money

At the end of this series on energy storage, perhaps the best message is an old one in investigations.

Follow the money.

There is no end of storage technologies: regular chemical batteries, flow batteries, pumped storage, flywheels, heat storage and even phase change materials.

Which one will change the face of the energy landscape? That’s not yet clear.

And one reason is cost. Most of these technologies are still very expensive. 

(Here is a good place to insert a notice of conflict. I am an elected member of an electric cooperative board of directors. If lots of people go off-grid, it certainly impacts the finances of the co-op, but as a community co-op it’s also our imperative to serve the members, so if that’s the better alternative for them…)

I talked a while back with the son of an old Wisconsin farmer, who remembers his dad turning down a battery-based electrical system for the farm. At the time, there was no electricity at the farm. Kerosene lamps illuminated the place, and humans or animals did the work, not electric motors.

He turned down the battery system, in part because it was far more expensive than the anticipated power line that an electric cooperative would soon provide him.

“I’ll wait for the wire,” he said.

It costs a utility in Hawai`i $.30 to $.45 per kilowatt hour to deliver power to your house, as it does in other areas dependent on oil-fired power. It's a lot of money. Running your own power system might seem like a slam dunk.

But follow the money.

You may spend $.20 to $.25 per kilowatt-hour or so to make photovoltaic power at home (less with the tax credits included, but they may not be around a lot longer). It can cost another $.25 to $.75 per kilowatt-hour to store that energy for nighttime use—the numbers are all over the place depending on technology and system size and financing. (If anyone wants to nitpick these numbers, I’d be pleased to hear from you.)

If those numbers are good approximations, then without even talking about maintenance, equipment replacement, damage repair and so forth, the cost of your power is at a minimum equal to utility power, and at a maximum much, much higher. 

And and if you’re your own power supplier, you have the added benefit, when the lights go out, of personally responding rather than waiting for a trained lineman.

This is not to say going off-grid can’t work. It has always made sense in some limited applications—like a remote location where up-front infrastructure costs are prohibitive or a utility line isn’t available at all. It is not an accident that most home power magazines describe remote homes, far from existing grids. 

And it’s not to say that going off-grid might not make economic sense soon. When the price to make the power drops to a dime and it costs another dime to store it, that’s when the big crossover comes.

We’re not there yet. But we may be there within a very few years.

For utilities, which benefit from economies of scale, certain storage applications already make sense, but even for them, those applications generally require special situations.

© Jan TenBruggencate 2013