One kind of dwelling was both natural and manmade caves 一种是天然或人造的洞穴。
2.
Natural and synthetic 天然或人造
3.
Flooding occurs when rainfall is so high that natural or engineered drainage fails to drain away the surface runoff . floods are usually fairly transient in the urban areas 当降雨率超过天然或人造排水系统的负荷时，积聚地面的雨水便不能及时排去，因而引致水浸。
4.
Flooding occurs when rainfall is so high that natural or engineered drainage fails to drain away the surface runoff . floods are usually fairly transient in the urban areas 当降雨率超过天然或人造排水系统的负荷时，积聚地面的雨水便不能及时排去，因而引致水浸。
