Whatcausesaflood?Floodsareoneofthemostcommondisastersin...

问题详情：

What causes a flood?

Floods are one of the most common disasters in the United States. Flood effects can be local, impacting a neighborhood or community, or very large, affecting several states.

  36   Some floods develop slowly，sometimes over a period of days. But flash floods can develop quickly, sometimes in just a few minutes and without any visible (看得见的) signs of rain. Rash floods often have a dangerous wall of roaring water and can take away most things in its path.

Floods happen when a watercourse (水道) overflows.  37 

Heavy rain

When the ground already contains a lot of water, the falling rain could not seep through it. The water then starts flowing toward a watercourse. When it rains a lot in a region, all water flows toward the river, but this river can not contain it.  38 

Thaw

When spring arrives, snow and ice start to melt and the water flows toward the river.  39   the river overflows and a flood happens.

Ice jam

In spring, rivers thaw out and pieces of ice drift on the river.  40   As a result, these pieces of ice form a kind of dam (水坝). When water cannot flow through this dam, it tries to find another course to reach the river and sometimes, this new course is a field, a road or a house basement.

A．We can think of some ways to prevent the flood from happening.

B．However, all floods are not alike.

C．Therefore, the river overflows.

D．Sometimes these ice pieces get jammed against a bridge or rocks.

E．They could be caused by heavy rain, thaws (解冻) or ice jams (*塞)．

F．One of the biggest problems people faced was lack of fresh water.

G．If the temperature rises too rapidly, a lot of water is produced in a short time.

【回答】

BECGD

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