2 sentences

1. 这里曾经是河床。

   zhè​lǐ céng​jīng shì hé​chuáng.

   This used to be a riverbed.

   Source: OpenSubtitles

2. 河床上的泥沙经过长年累月的积淀，形成了新的小岛。

   hé​chuáng shàng de ní​shā jīng​guò cháng​nián​lěi​yuè de jī​diàn, xíng​chéng le xīn de xiǎo dǎo.

   The silt on the riverbed accumulated over the years to form a new island.

   Source: Dong Chinese Dictionary