Josef, I'm unable to find any topography maps of Oporto. The Douro River would be the greatest concern. For two reasons. 1-The slight possibility of a tidal surge from the winds blowing ahead of Hurricane Vince. And 2-possible river flooding from excessive rainfall. So areas near the Douro River and any streams that flow into the Douro river could be in danger of flooding, either from rainfall or from water being pushed ahead of the storm.