Sediment, Earth And Sand
noun
Earth and sand is earth and sand, or sediment.
どしゃ
This is a jukugo word and it uses the on'yomi for both kanji. This on'yomi for 砂 is a bit less common, and you haven't learnt it yet, so here's a mnemnonic to help you: If there's too much sediment, you need to speak to a shaman (しゃ) about it. Only a shaman has the power to get rid of all that earth and sand and get the river flowing again.
川底にはたくさんの土砂がたまっている。
There's a lot of sediment in the riverbed.
津波で大量の土砂が二階の教室に流れ込んだ。
Due to the tsunami, a large amount of earth and sand flowed into the second-floor classroom.
地震の後には土砂災害の危険があります。
After an earthquake there's a danger of landslides.