冲积

chūn xùn shí chōng jī le yī céng shā tǔ

春汛时冲积了一层沙土。

When the spring floods come, the alluvium forms a layer of sand and soil.

hé biān de qiǎn tān shì chōng jī ér chéng de

河边的浅滩是冲积而成的。

River shoals are formed through alluviation.