Retention Basin used as Park?

Hi, I’m trying to add some detail in AZ having lived there for a long time. However, a lot of the parks have a large grassy area used for general recreation that are used as a retention basin when it rains heavily (so maybe a couple of times a year). Should these be tagged as a retention basin within the park/ seperate from the park or left out altogether?

I think the detention pond should be tagged within the park. Usually detention facilities are meant to be flooded during usual heavy rainstorms, however during normal 100 to 500-year floods, the park is allowed to be flooded. Is there a permanent body of water in the park as you mentioned that you were tagging in AZ? In TX, there is usually no permanent body of water so I mainly use basin=detention instead of basin=retention (