Hurricanes draw their strength from the sea, so they quickly weaken and begin to dissipate when they make landfall. Hurricanes moving over fragmenting marshes toward the New Orleans area can retain more strength, and their winds and large waves pack more speed and destructive power. Scientists working for the Louisiana Department of Natural Resources measured some of these effects during Hurricane Andrew in 1992. Andrew's surge height dropped from at Cocodrie to at the Houma Navigation Canal to the north. For every mile of the marsh-and-water landscape it traversed, it lost 3.1 inches of height, sparing some homes farther north from more flooding. Currently Louisiana has 30% of the total coastal marsh and accounts for 90% of the coastal marsh loss in the lower 48 states. The engineering of the river has basically brought the Gulf of Mexico much closer to New Orleans, making it more vulnerable to hurricanes.