00 families.A main source of silt in urban rivers is disturbance of soil by 建筑施工 activity. A main source in rural rivers is侵蚀作用from plowing of farm fields, 皆伐 or 刀耕火耨 treatment of 森林s.
文化象征.尼罗河河岸上的黑色淤泥在古埃及是重生的象征，往往与之一的阿努比斯（Anubis）相关