The level of flooding that Harvey has caused in Houston has traditionally been expected once every 500 years, but in fact "500-year floods" have happened 3 times in Houston in the last 3 years.
Daadadka masiibada ayaa noqotay wax cusub oo ay kujirto Harvey,Houston waxaa ku dhacay saddex dhacdo '500 sano oo daad ah' saddexdii sano ee la soo dhaafay.