Comprensión auditiva TOEFL

🎧 Transcripción de audio

Narrator: Listen to part of a lecture in an environmental science class. Professor: Today we're going to talk about a surprising solution to urban flooding: green roofs. Now, you might think that a roof covered in plants is just for aesthetics, but there's real science behind it. When rain falls on a conventional roof, it runs off quickly, overwhelming storm drains and causing floods. A green roof, however, acts like a sponge. The soil and plants absorb and retain a significant amount of rainwater, slowly releasing it back into the atmosphere through evaporation and transpiration. Studies have shown that green roofs can capture up to 80% of rainfall during a typical storm. But there's a catch: their effectiveness depends on the depth of the growing medium. A shallow green roof, say, less than 10 centimeters deep, works well for small storms but saturates quickly during heavy downpours. Deeper systems, over 15 centimeters, can hold more water but are heavier and require structural reinforcement. So, engineers must balance water retention with building capacity. Also, the type of plants matters—native species with deep roots are more effective than shallow-rooted succulents, which are often chosen for their drought tolerance. So, while green roofs aren't a one-size-fits-all solution, they represent a promising tool in our flood management toolkit.