Snowmelt, rain, ice and tides routinely deliver unpleasant surprises to Mainers in the form of flooding. Factor in the sea-level rise scientists predict from global warming and it can be hard to anticipate where and when coastal flooding might occur. But a collaboration between researchers and a Maine software firm could help municipalities plan for future flooding, in a way that minimizes the associated costs.

Patrick Cunningham is standing near Cobbosseecontee Stream in downtown Gardiner. "We're down underneath the bridge that is behind Water Street in Gardiner, and we are standing next to the high-water mark for this area from flooding from this tributary off the Kennebec River," he says.

Murray Carpenter: "So this marker--the water would be 10 feet above our heads during a 100-year flood, and if we look around, this is a parking lot, there's apartment buildings, all kinds of things to flood here."

Patrick Cunningham: "Absolutely, yeah, we would be under water right now, and in the eight years that we've been in this office up the hill there, it's definitely gotten over our waists here--a couple of times."

Cunningham is president of Blue Marble Geographics, which develops software for mapmaking. He is now collaborating with researchers from the University of Southern Maine and the University of New Hampshire to create maps showing where flooding could occur, and what it will cost.

The maps incorporate data from many sources, including the Army Corps of Engineers, and the National Oceanic and Atmospheric Administration.

"So, you're talking about storm surge and sea level rise scenarios and the damage associated with those events," Cunningham says. "What will my damage be if I do something or if I do nothing? And what would that look like maybe today, 20 years out, a hundred years out? So you are modeling the scenarios that and what you are providing the end user and hopefully the public is a visualization tool so you can communicate that very easily and clearly."

At his office computer, Cunningham pulls up a map of Portland's Back Cove area, with flooding information displayed as a Google Earth overlay. It includes property values gleaned from tax assessors' files.

"And the darker-colored parcels are the ones that have the deeper water," he says. "This deep water here is near that U-Haul area. Right now, naturally occurring with a storm, they are getting puddles of seawater in these areas, and people are already affected by that. So this is Play it Again Sports, and we can click on that, and we can look at some of the data: This isn't cleaned up yet but you can see that the damage here, based on the value of the building and the area, is in the millions of dollars."

Sam Merrill, of the Edmund Muskie School of Public Service at the University of Southern Maine, has been working for years to develop the modeling tool, known as COAST. He says it is more powerful than standard maps that simply show where flooding will occur.

"What's really been missing, and where I think the COAST tool and approach adds value, is it helps communities have a real conversation about costs and benefits of taking different kinds of action, versus doing nothing," Merrill says.

Merrill says flood-proofing actions can range from building levees or sea walls to raising buildings or roads. It could also mean changing zoning, steering development to less flood-prone areas, or modifying buildings so that when floods do occur, water flows through with minimal damage.

"What's really exciting to me about this is that it's an opportunity for communities to engage with the question of what are we going to do for the next 100 years?" Merrill says. "And it's not like sea level rise is going to stop in the year 2100. But we have some real decisions to make, and we do have options, besides simply allowing destiny to wash over us."

Merrill has been collaborating with Paul Kirshen of the University of New Hampshire. They have used the COAST model to understand the costs of flooding in Hampton, New Hampshire, and Groton, Connecticut. But Kirshen says it could be applied internationally.

"Most of the world's large cities, both in the developed, as well as the developing, world are along the coastline, and they all have the same problem, most of them do--increased flooding from higher storm surges," Krishen says. "And they all are going to be faced with the same problem: 'How do we adjust, or adapt to this?'"

Merrill says the first full version of the model should become a freely available download next summer. The first users will likely be municipal planners with computer mapping skills.