This map looks like a topomap. According to said map, I will be 1 meter underwater in a 100 year flood. But the map also looks to ignore the 4 meters of steel

This map looks like a topomap. According to said map, I will be 1 meter underwater in a 100 year flood. But the map also looks to ignore the 4 meters of steel/concrete lined channel that run behind my neighborhood. FEMA puts me in zone X (500 year flood zone).