It had been raining for seven years, thousands upon thousands of days compounded and filed from one end to the other with rain with the drum and gush of water with the sweet crystal fall of showers and the concussion of storms so heavy they were tidal waves come over the islands. A thousand forests had been crushed under the rain and grown a thousand times to be crushed again. And this was the way life was forever on the planet Venus.
The above extract is from "All summer in a day" written by Ray Douglas Bradbury. I couldn't understand what it meant by 'with the drum and gush of water with the sweet crystal fall of showers and the concussion of storms so heavy they were tidal waves come over the islands'. I searched over the internet and asked my friends but no one was able to explain the meaning. Could someone explain what is meant by the above mentioned lines?