Late Tuesday evening Isaac came ashore as a category 1 hurricanenear the mouth of the Mississippi River in southeastern Louisiana,drenching land stretching into the Gulf of Mexico and causingwidespread power outages.

Packing more of a punch than originally projected, Isaac knockedout power lines and compelled several reluctant evacuees to retreatto their roofs while awaiting emergency rescue. Reportedly threeadults and an infant were rescued overnight via houseboat.

Entergy and Cleco power companies estimate that more than half amillion—approximately 522,000—customers are currently without powerin Louisiana, Mississippi and Alabama as a result. Companyrepresentatives cautioned that attempts to restore power will notbe initiated until Isaac's winds fall below 30 miles per hour.

Many fear the worst is yet to come. Although the slow-movingstorm is much less powerful than Katrina, which smashed into NewOrleans with unrelenting force seven years ago today, Isaac'sviolent winds and oppressive rains are already testing themultibillion-dollar barrier system put in place after Katrina.

Earlier today, the hurricane pushed water over a levee on theoutskirts of New Orleans, but despite mixed reports, did not breachthe levees built to protect the city. Emergency officials inPlaquemines Parish, however, did cite the “overtopping of an 8-foothigh levee” between the Braithwaite and White Ditch districtssoutheast of New Orleans.

Heavy rains are expected to persist in the coming days, and theimmediate concerns are storm surge and massive flooding. Havingalready caused an estimated $1 billion in economic losses foroffshore energy properties, Isaac's impact on land-dwellingenterprises could be even higher. Eqecat has projected that variouscategories of insured losses along the coast of the U.S. Gulf ofMexico could reach $1.5 billion. A more robust estimate is expectedto be released once the storm passes over New Orleans.