Isaac still had some punch Thursday as it weakened to a tropical depression and moved slowly north from the Gulf Coast. Emergency management officials warned even coastal areas were still at risk, The New York Times reported. \"Whether a community is beginning the cleanup process, or still feeling the effects of Isaac, residents still need to be alert to the dangers that remain,\" said W. Craig Fugate, head of the Federal Emergency Management Agency. \"This is still a powerful storm and there are a number of areas both along the coast and inland that can be affected by strong winds, storm surge and inland flooding and tornadoes.\" The Hydrometeorological Prediction Center in College Park, Md., said Isaac was expected to move up the Mississippi Valley Friday, turning northeast up the Ohio River Saturday. Late Thursday, the center of the depression was about 85 miles northeast of Shreveport, La. Forecasters with the center said the drought could prevent flash flooding in many areas, but the risk would increase if heavy rains persist. Some areas in Florida and Louisiana have already received more than a foot of rain from Isaac. In New Orleans, defenses put in place in the seven years since Hurricane Katrina protected the city, the Times said. But communities on the north side of Lake Pontchartrain flooded, and in some places levees actually held floodwaters in place. Louisiana Gov. Bobby Jindal said about 6,000 people were registered at storm shelters and 3,000 had to be rescued.