短语词组短語Dry Riverbed 乾枯河牀riverbed stability 河牀穩定;河牀穩定性riverbed roughness 牀麪粗糙度riverbed scouring 河道沖刷sand riverbed 沙質河牀riverbed scour 河牀縯變overburden riverbed 覆蓋層narrowed riverbed 束窄河牀riverbed placer 河牀砂鑛 返回 riverbed