Hundreds of residents downstream of flooded of Jackson fled their homes yesterday as the surging Pearl River defied forecasts and edged higher. In Alabama, thousands were evacuated from the threat of new flooding.

And the Army Corps of Engineers said it would open the Bonnet Carre Spillway, hoping to slow the rising Mississippi River before it strains the levees protecting New Orleans.

Jackson officials have estimated that more than 17,000 persons already have been flooded out in the metropolitan area, but sandbag levees designed to stem the rising Pearl were holding.

About 40 milles downstream at Georgetown, mobile homes and packed cars headed to the only open road leading from the community of 420 residents.

Still further downstream, evacuations were under way at Monticello and Columbia, where the river continued a steady two-foor daily rise toward expected record crests late this week. Officials in Columbia said as many as 2,000 persons might be evacuated.

In Alabama, the number of people evacuated because of floods rose toward 5,000 with as many as 3,000 people in ana dround Selma being evacuated. More than 600 families were evacuated at Demopolis. CAPTION: Picture, Residents of Arnold, Mo., negotiate flooded street. AP