How is flood management done abroad? Delhi, Mumbai or Porbandar… our cities are drowning, same havoc everywhere

Unrestrained rain. Then uncontrollable floods that destroy cities. Whether the city is big or small, everyone drowns. Delhi, Mumbai, Vadodara or Patna. All are facing the same disaster. Either the flood from the sea drowns them. Or the overflowing of the river. This is natural. But the water management system of the city also drowns