Well the most important thing is to fix the drainage. I would highly recommend you pay for (if you can at all afford it and you might avert more costly disaster later - a flood into your home) a drainage expert and should be a landscape ARCHITECT would be the one. Please do not think a flood cannot happen that this house has never flooded. I am a flood "survivor" and have seen many houses flooded. Just watch the news and you won't believe how many little streams and rivers have carried houses away. Not to be overly dramatic but I'm on a crusade I guess. Please also have flood insurance - really. The next thing would be to possibly build a pond, "dry" stream bed (will be wet during flood times), and / or "rain gardens." The bad news is all these things won't really work if the whole yard basically floods and the draninage really needs to be fixed first. Sorry and good luck. Laurie