It only took a modest flow  through the emergency spillway to reveal the true geologic conditions: the hillside was  composed almost entirely of highly erodible soil and weathered rock.

只需通过紧急溢洪道的少量水流即可揭示真实的地质条件：山坡几乎完全由高度侵蚀的土壤和风化的岩石组成。