ISTANBUL—The death toll from severe floods and mudslides in coastal Turkey has climbed to at least 40, the country’s emergency and disaster agency said Saturday. Torrential rains that pounded the Black Sea provinces of Bartin, Kastamonu, and Sinop on Wednesday caused flooding that demolished homes, severed at least five bridges, swept away cars, and rendered numerous roads unpassable. Turkish disaster agency AFAD said 34 people were killed in Kastamonu and six in Sinop. Nine people remained hospitalized in Sinop and one person was missing in Bartin province, according to the agency. But some residents said on social media that there are hundreds more missing, a statement also made by an opposition lawmaker. About 2,250 people were evacuated across the region, some lifted from rooftops by helicopters, and many were being temporarily housed in student dormitories, authorities said. Experts in Turkey say interference with rivers and improper construction were contributors to …