A placer gold area is usually distributed in the flowing regions of plain terrain, belt-like rivers.
砂金地区一般分布在地形平坦、呈带状的江河流域。
Niukouyu area is situated in the hilly terrain about 2km southwest of Fangshan Town, Beijing, at the boundary between the Taihang Mountains and the North China Plain.
牛口峪地区位于北京房山县城西南2公里的华北平原与太行山脉交界的丘陵地带。
As the terrain in plain region is flat, the topographical height difference for the drainage pipeline cannot be utilized so as to cause the pipelines in the lower reaches are buried too deeply.
平原地区由于地势平坦，排水管道往往无地形高差可以利用，造成下游管道埋深过大。
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