Powerful Hurricane Ida has battered the southern US state of Louisiana and plunged New Orleans into darkness, leaving at least one person dead 16 years to the day after Hurricane Katrina devastated the city.

Ida slammed into the Louisiana coast as a Category 4 storm but had weakened to Category 1 by Sunday night.

President Joe Biden, who described Ida as “a life-threatening storm”, declared Louisiana a disaster area.

One person was killed by a falling tree in Prairieville, 130km (60 miles) northwest of New Orleans, the Ascension Parish Sheriff’s Office said.

Louisiana Governor John Bel Edwards said Ida could be the most powerful storm to hit the state since 1850.

Governor Edwards warned Ida would be “a very serious test for our levee systems”, an extensive network of pumps, gates and earthen and concrete berms that was expanded after Katrina.

The storm is expected to continue weakening as it moves over land with a predicted track taking it north over the central US before veering eastward, reaching the mid-Atlantic region by Wednesday.