“We’ve been campaigning for 25 years to bring investment to our community,” said Rita McInerney, a local businesswoman. “There is a not a lot of opportunity for employment here. They already employ 250 people there in the summer, and there’ll be more if they feel they can expand it. We’ll continue to work with the owners, whoever they are.”

Records show that Mr. Trump paid 8.7 million euros for the resort at an auction in 2014. It had originally opened in 2002, having cost €28 million to build.

Environmentalists said the new coastal walls would damage a popular public beach and vulnerable dunes and heath. Some residents also objected, saying the walls would alter tidal flows and divert storm surges into their own properties.

The leader of the Irish Green Party, Eamon Ryan, who objected to the application, said the party was disappointed in the decision and would consider filing an appeal.

“The best advice we had was that it would be better to move the golf holes farther inland,” he said, “where there’s room for them, rather than disrupt the beach.”