How will the AHS affect water levels upstream and downstream of the AHS barrier?  By

How will the AHS affect water levels upstream and downstream of the AHS barrier?

The City of Grand Rapids completed negotiations with FEMA regarding its floodwalls; the plans to construct the AHS was cited as one reason why the city is not being required to build higher floodwalls.  During sea lamprey barrier operations the river level within the main channel upstream of the AHS may be elevated for longer periods.  However, during flood flows that affect structures the barrier will be operated to slightly reduce the elevation of flood flows from the existing condition.  Properties that currently flood on a regular basis will continue to flood on the same interval.  The 100-year flood elevations will not be impacted.