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 research shows it can significantly reduce stormwater runoff. In a traditional city, when it rains, water hits impermeable surfaces like concrete and asphalt, and it rushes into sewers, often overwhelming them and causing floods. A green roof, however, absorbs rainfall like a sponge. The soil and plants hold onto the water, and then release it slowly through evaporation and transpiration. Some studies in cities like Toronto and Portland have found that green roofs can retain up to 60% of annual rainfall, depending on the depth of the soil and the types of plants. This not only reduces flooding but also lessens the burden on wastewater treatment plants. Plus, green roofs provide insulation, cutting energy costs for heating and cooling, and they create habitats for birds and insects in dense urban areas. So, while the upfront cost is higher than a conventional roof, the long-term benefits are substantial. Any questions?
❓ 题目 What is the main point the professor makes about green roofs?
A. They are primarily decorative and add aesthetic value to buildings.
B. They are an effective tool for managing stormwater and reducing urban flooding.
C. They are too expensive and not worth the investment for most cities.
D. They are most useful in areas with high annual rainfall, like tropical regions.
✅ 正确答案
They are an effective tool for managing stormwater and reducing urban flooding.