短语词组短语Dry Riverbed 干枯河床riverbed stability 河床稳定;河床稳定性riverbed roughness 床面粗糙度riverbed scouring 河道冲刷sand riverbed 沙质河床riverbed scour 河床演变overburden riverbed 覆盖层narrowed riverbed 束窄河床riverbed placer 河床砂矿 返回 riverbed