Flood warning: Baltimore, Annapolis, Ocean City seen getting wetter much more often

With minor flooding forecast Wednesday morning for Baltimore and elsewhere along the western shore of the Chesapeake Bay, there's a new warning that rising seas are likely to encroach more often and reach farther inland in coming decades.

The National Weather Service issued a coastal flooding advisory Tuesday night for Anne Arundel, Calvert and Harford counties and southern Baltimore. Onshore winds combined with higher than normal tides were expected to cause "minor shoreline inundation" in low-lying areas.

A report issued Wednesday by the Union of Concerned Scientists says tidal flooding already is happening more often than it did in the past in coastal communities like Baltimore. With sea level predicted to rise by a foot over the next 30 years, the environmental group warns, such periodic disruptions could become a chronic problem, closing streets and driving people from homes and businesses on a regular basis.

The union's report is just the latest of several to warn of increased coastal flooding, but it goes further than earlier missives in predicting how often some 52 Atlantic and Gulf coast communities will get wet, and how badly.

In Baltimore, for instance, the report projects the number of tidal floods could increase 10-fold over the next three decades, to more than 225 inundations a year. And minor "nuisance" flooding caused by high tides, such as what was predicted for Wednesday, could become more extensive, staying longer and causing more damage and disruption.

By 2040, the report says, Annapolis could see at least some flooding almost daily -- more than 360 times a year -- with about 50 extensive inundations. Parts of Maryland's capital might never be dry again, the report's authors say.

And in Ocean City, which experiences tidal flooding about eight times a year, the report says the frequency could more than triple to 30 events over the next 15 years. By 2045, floods could multiply dramatically to more than 170 a year, it projects.

Though prompt action to curb climate-altering pollution might temper the changes under way, it's too late to halt rising seas, the report says. Past and present emissions of carbon dioxide, methane and other greenhouse gases have already set in motion the processes that will lead to more flooding.

The group recommends communities begin working now, though, to limit the damage and disruption by flood-proofing existing structures and neighborhoods, as well as infrastructure such as sewer and water systems. Planners also are urged to curtail new development in coastal areas susceptible to tidal flooding.

The report highlights steps some of Maryland's communities are taking. Ocean City, for instance, now requires developers to elevate new buildings, and the town has drafted a policy to raise flood-prone streets as it performs periodic upgrades.

Baltimore, meanwhile, is including climate-change impacts in rewriting the city's disaster and hazard mitigation plan, the report notes. And steps have been taken toward requiring flood-ready building designs in the city's 500-year floodplain.

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