Complex sentence: The dam operators apparently sounded a warning siren shortly before the dam failed, sending a surge of water and debris up to high into the town of Cirendeu, washing away cars, houses and a brick-built bridge.
Split into simpler sentences: The dam operators apparently sounded a warning siren shortly before the dam failed. A surge of water and debris up to high was sent into the town of Cirendeu, washing away cars, houses and a brick-built bridge.