Although the restoration of Cheonggyecheon was initiated in a bid to restore historical and environmental values, the safety issues including flood prevention came to the fore in the course materialization. The city set the target flood recurrence interval of 200 years. Given that other 2nd-grade local streams were managed based on 50-year interval assumption, it was a decision to better ensure the citizens' safety by securing sufficient stream capacity to deal with local torrential rainfalls. The city also strived to secure discharge area by excavating the underneath of both banks