Gravel pit to wetland flood buffer

I’m planning staged rewetting and native seeding at a 6-acre decommissioned gravel pit outside Fort Collins to slow peak flows, kickstart ecosystem repair, and add sustainable flood resilience. If you’ve balanced detention specs with biodiversity goals, how did you manage 0.3–0.5 m seasonal water swings without spiking methane or inviting reed canarygrass?

‌⁠‍⁠​‍​‍‌⁠‌​​‍​‍​⁠‍‍​‍​‍‌‍⁠​‌‍​‌‌‍⁠‍‌‍‌​‌⁠​⁠‌‍​⁠‌‍​‌‌⁠​​‌‍‍‌‌‍⁠‍‌‍‌⁠​‍​‍​‍⁠​​‍​‍‌‍‍⁠​‍​‍​⁠‍‍​‍​‍‌‍⁠‍‌‍‌‌‌⁠‌⁠‌‌⁠⁠‌⁠‌​‌‍⁠⁠‌⁠​​‌‍‍‌‌‍​⁠​‍​‍​‍⁠​​‍​‍‌‍‍‌‌‍‌​​‍​‍​⁠‍‍​‍​‍‌‍⁠‍‌‍‌‌‌⁠‌⁠​‍​‍​‍⁠​​‍​‍‌‍‌​​‍​‍​⁠‍‍​‍​‍​⁠​‍​⁠​​​⁠​‍​⁠‌‌​⁠​‌​⁠​​​⁠​‍​⁠​‍​‍​‍​‍⁠​​‍​‍‌‍‍​​‍​‍​⁠‍‍​‍​‍​⁠‌‍‌​‌‍‌​‌‍​⁠‌⁠​⁠‌‌‌⁠​‍​⁠​‌​⁠‌‍‌​⁠⁠‌‌​⁠‌‌‍​‌‍⁠⁠‌‍​‍‌⁠‍‍​⁠​‌​⁠​‍​‍​‍‌⁠⁠‌