ShoreZone: A Low-Tide Photo Map of Alaska's Coastline

In December 2012, Shell's Arctic drilling rig Kulluk was being towed across the Gulf of Alaska when a storm blew up. In 18-foot seas the towline broke, and a few days later the rig ran aground on Sitkalidak Island with 140,000 gallons of diesel aboard.

The Coast Guard and other responders needed to know at once what kind of shore it had hit. "Is it a sandy beach, or is it a jutting rock cliff that will pulverize the rig when it hits?" as a NOAA Fisheries biologist put it. "Are there salmon streams nearby, or nursery grounds for important fisheries, or other sensitive habitats that need to be protected?"

Alaska's coastline is longer than that of the lower 48 states combined, and most of it is remote and empty. In midwinter, with little daylight, a quick flight to look was no help.

A virtual flyover

Instead, responders took a virtual flight along the shore in ShoreZone, an online archive that works something like a street-level map for the Alaska coast. Better still, its pictures show the shore in summer at extreme low tide, with the whole intertidal zone exposed. "At low tide you can see cliffs, rock ramps, stream deltas, all kinds of features that are usually hidden," the biologist said, features that can reach a kilometer or more from shore.

The pictures are taken from a helicopter with its doors removed, during the 5 days each month with the lowest tides, and only in the 4-hour low-tide window on each of those days. Satellites could rarely be scheduled for those exact hours, and clouds would probably block the view if they were. Above all, the helicopter's slanting view shows the shore in three dimensions, which a straight-down satellite image cannot. Around small island groups, rock reefs, inlets and deltas, the crew flies tight circles to get the detail that habitat mapping needs.

Born of an oil spill

The idea came after the Exxon Valdez spill. To judge the damage, biologists needed to know how much eelgrass, an important nursery for young fish, including many valuable species, grew in Prince William Sound. No one knew.

Now that kind of information is easy to find, not only for Prince William Sound but for the more than 80% of Alaska's coast already in ShoreZone. Users can view and download photos and video, search detailed habitat descriptions, and download maps of the shore for GIS.

Most simply download the pictures, which are full of information in themselves. Colored bands along the shore mark the small habitats of the intertidal zone; scars on rock show where winter ice scours the coast; and as the climate warms, great blocks of permafrost can be seen breaking off into the sea, the edge of a coast in retreat.

Who uses it

ShoreZone is used to plan for oil spills, by rescuers heading to boats in distress, and by scientists choosing field sites. NOAA Fisheries and other agencies use it to identify important fish habitat, review permits for industrial projects and track invasive species. Alaska Native communities use the images to judge the risk from eroding shores and rising seas, and as the pictures make plain, many of those villages will soon have to move.

The pictures are also beautiful: detailed records of life where land meets sea, along one of the richest and most vulnerable coasts on the planet.

Sources

• NOAA Fisheries, "ShoreZone: Art Meets Science on the Alaska Coastline"; rewritten in hubnx's own words. The source's photographs are credited to Alaska ShoreZone and are not reproduced here; they can be seen in the ShoreZone archive.