You are given a sentence in Persian. Your job is to translate the Farsi sentence into English.

پیاده رو ها از جنس شن بوده و هنگام بارندگی دچار ظغیان و بالا آمدن می شوند. اما هنوز سبز هستند.

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
The sidewalks are gravel. They flood when it rains, but they're green.