Flood
It has rained four inches in the last 12 hours and the boxes stored in your basement are under water.
Your stream has risen dramatically and found its way into your basement submerging your mechanicals.
Your homeowner policy does not respond to a “flood” situation. A flood policy may respond depending on certain factors and the company providing the coverage. It is worth investigating. Note that you do not have to live next to a body of water to need flood insurance.