(一)在黄河中游黄土陡崖深沟地带,常因地震或重力等作用,造成巨量坍方。坍方闸住山沟,截断河流,拦住泥水,形成天然拦泥埙,当地群众叫做“聚湫”。这种天然垠,北至鄂尔多斯沙漠边缘,南至秦岭,东至吕梁山,西至兰州的广大地区里都大量存在,尤以六盘山附近的黄土残塬区和丘陵沟壑区最多。这种天然拦泥坝,既无溢洪道也无泄水洞,坝前 (A) In the middle reaches of the Yellow River loess ditch deep groove zone, often due to earthquakes or gravity and other effects, resulting in massive collapse. The slump blocked the ravine, cut off the river, stopped the muddy water and formed a natural mud embankment. The local people called it “poly ramie.” This natural Eun, north to the edge of the Ordos desert, south to the Qinling Mountains, Luliang Hill to the east, west to Lanzhou in large areas are abundant, especially in Liupanshan loess plateau and hilly areas up. This natural mud dam, there is no spillway nor the drainage hole, the dam