WASHINGTON — Last month’s deadly tsunami wreaked havoc underwater too: Waves smashed navigation buoys, dragged sandbars into shipping channels, lifted reefs and other obstacles hundreds of feet in some spots and tossed debris everywhere.

Navy cartographers say navigation through the Indian Ocean will be problematic for years due to last month’s violent earthquake and deadly tsunami, both of which altered normal shipping routes.

“Most of those charts have to be redone,” said Steve Honda, spokesman for the National Geospatial-Intelligence Agency. “Until we actually get out there, we won’t know how much has changed.”

Officials from the U.S. Geological Survey said most non-sailors won’t notice the changes; typical textbook maps and reference globes don’t show the area in enough detail to highlight the geographical shifts.

But for sailors and commercial ships, the changes complicate movement through the region. Honda’s agency, which is responsible for the U.S. Navy’s nautical guides, already has received one unconfirmed report from a commercial ship in the region that the ocean floor rose nearly 1,000 feet in an international shipping lane.

Other research has shown miles of sandbars shifted and coastlines collapsing into the sea, according to Mark Jarrett, deputy director of the Naval Oceanographic Office’s Survey Operations Center.

“We’ve been asked to go in after hurricanes to check our maps, but we’ve never seen anything to this scale,” he said.

The undersea confusion has further complicated getting aid to devastated countries, since larger ships cannot easily move into major ports because of debris obstacles. Jarrett said so far most of the supplies being moved into ruined areas have been airlifted in or transported on hovercraft-type boats, both of which are expensive.

NGA officials have issued a general warning about the potential navigation issues for ships in the region, but won't be able to offer specific route changes until surveyors can examine the area.

Jarrett said his office already has dispatched a fleet of surveyors to the region to begin rebuilding charts, especially those surrounding major ports.

Ultimately replacing markers and updating maps near the shoreline will fall to the countries affected, but U.S. personnel are now putting together initial sketches of what is in the water.

“We can tell people what debris is clogging channels, what buoys are left and put in temporary markers,” Jarrett said. “Eventually, this will require us to go back and completely rebuild charts. But we can do a rough survey in a day, maybe hours.”

Survey crews launch from naval ships in the area on seven-foot rigid-bottom rafts, and use portable sonar devices to scan for potential hazards. Jarrett said once collected, that information can be transmitted to military personnel in the area almost instantaneously, giving them a larger view of what is below than their ships’ sonar systems can.

Only eight surveyors are currently in the region; Jarrett said another ship with personnel and equipment is en route to help map hundreds of miles of critical underwater channels.

Honda said even with more personnel the process of rebuilding the navigation charts won’t be finished anytime soon.

“We’re talking about a process that’s not days but years,” he said.

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