Final answer:
Waterway closures can be caused by natural events such as debris flows, human activities including construction, natural barriers like waterfalls, and environmental changes like sea level rise and extreme weather events.
Step-by-step explanation:
There are several scenarios that could result in waterway closures. One significant cause is when slope materials become saturated with water, leading to debris flows or mudflows. Such events can carry along rocks, mud, and even larger debris such as trees, houses, and cars, becoming a blockage to the waterway and causing flooding.
Another scenario involves human activities such as road construction or the building of infrastructure like weirs for flood prevention, which can hinder or completely stop water traffic. In addition, natural obstacles such as waterfalls have historically served as points where water transportation must pause, creating a head of navigation that requires cargo to be carried around the impediment.
Lastly, environmental changes like sea level rise, extreme weather events, and increased river activity from infrastructure projects like dams can lead to waterway closures. These environmental factors not only affect human activity but also have significant impacts on animal species, potentially leading to changes in their habitats or even extinction.