Municipalities looking to build ‘sponge cities’ for extreme rain events. What does that mean?

"Sponge parks" in Montreal are designed to catch and absorb rainwater and keep it from flowing into overburdened sewers during extreme rain events.

Municipalities looking to build ‘sponge cities’ for extreme rain events. What does that mean?
"Sponge parks" in Montreal are designed to catch and absorb rainwater and keep it from flowing into overburdened sewers during extreme rain events.