Deforestation點樣lead to Flooding?

Deforestation means the cuting down of trees
so the ground is no longer covered by trees
and therefore exposed to rain

why does deforestation lead to flooding?
(as far as i remember) this happens in dry areas
expecially in deserts
you know deserts are usually dry
but they suddenly get a lot of rain
2-3 times a years (or so)
these rain events are usually very heavy

the ground with no trees would be further dried to make a hard surface
(look at this picture: http://www1.istockphoto.com/file_thumbview_approve/143696/2/istockphoto_143696_dry_ground_with_lumps_and_cracks_in_the_soil.jpg)

this picture shows the hard soil that is produced after deforestation and rapid dehydration of the soil
this soil becomes very hard and compact
so when heavy rain comes, the rain water cannot percolate down into the soil
this is why flooding is caused!!!


hope this helps
thankx for your question

樹木的作用有抓緊soil的能力，

而Deforestation，把大量的樹木砍伐，

令soil變"鬆"，

當有大量的雨水時，因soil沒有被樹木抓緊，

便會造成Flooding了