Coastal erosion is a problem for homeowners up and down the Atlantic and Gulf coasts. But the East Coast isn't the only place where the ocean is encroaching on the shore. A case in point: Haleiwa, Hawaii, where ocean waves over Christmas chewed a big chunk out of five oceanfront properties. The Weather Channel reports on the holiday washout here (see: "Fast-Moving Erosion Threatens Hawaii Coastal Homes," by Audrey Mcavoy/Associated Press).

"The Christmas swell damaged at least five oceanfront properties in the neighborhood, rekindling a decades-old debate about how best the state and homeowners should respond to beach erosion and the increasingly rising waters of the Pacific Ocean," the Weather Channel reported.

In the short term, homeowners got permission for emergency measures. When one of the affected families ran out of sandbags, they built their temporary barricade using polka-dot pillow cases from Walmart.

But a longer-term defense against the erosion, such as an armored seawall or an artificial dune, would require environmental permits—and permanent measures to fight erosion have drawbacks. The University of Hawaii maintains a website documenting the island state's changing coastline ("Hawaii Coastal Erosion Website"), with interactive maps showing where beaches have shrunk and where they've widened. The website notes: "When erosion threatens the built environment a common reaction is to armor the shoreline with a seawall or revetment. Armoring may impound sand thereby impacting the sediment budget of a beach and exacerbating the erosion. Shoreline armoring also increases wave turbulence and reflection. It is common to find that the construction of one seawall on a beach leads to proliferation of additional seawalls. Armoring a chronically eroding coast leads to beach loss (Fletcher, et al., 1997). In an era of accelerating sea-level rise (Church and White, 2006) the threat of chronic erosion and beach loss is growing."