PORT ARTHUR, Texas (AP) — As the nation plans new defenses against the more powerful storms and higher tides expected from climate change, one project stands out: an ambitious proposal to build a nearly 60-mile "spine" of concrete seawalls, earthen barriers, floating gates and steel levees on the Texas Gulf Coast.

Like other oceanfront projects, this one would protect homes, delicate ecosystems and vital infrastructure, but it also has another priority — to shield some of the crown jewels of the petroleum industry, which is blamed for contributing to global warming and now wants the federal go...