Flooding can happen around any source of water. Especially river tiles. Flooding destroys property in cities. Swamps: The more nearby swamp tiles near the source of water, the less likely flooding is. And the less extreme of flooding. Swamp tiles won't be the best source of resources though. Jungle and to a lesser extent forests will also help a little bit with flooding. Jungle: Besides providing more resources then in civ 3 jungle could be a source of medical tech. IRL nature has been the source of inspiration for much scientific advancement both medical and not. But especially medicinal, many a med even being just a synthetic version of natural plant chemicals.