in regards to the guy with the french drain. that flooded when you got 9" of rain (well beyond 100year storm)
easiest solution would be to take a roof leader or two and divert them to a subsurface leaching chamber to ensure that it does not happen again.
i am going to assume you do own the house/own the land - ie not a condo/rental.
layman version of figuring out where to put.- unless you have a walkout basement.
walk around the house, your first floor sill should be level -measure down to ground from sill the lowest point is the largest distance to ground.
sewer or septic system? if septic, make sure you are not working @ the septic system location.
what is your ground like? gravel? sand? dirt? ledge? ie easy to dig into or not. lets Assume(ya i know what assuming does) it is not ledge and is not clay (ie pretty permeable) and the ground is ok for perculation rates.
pick a spot that is ~10ish feet from the house near the lowest point and a decent distance from the property line- ie front yard or back yard, sides are ok if you have ~20+feet to the property line- also direct distance from 1 or 2 downspouts.
buy two of these(or similar) with 2 ends and hook them both together per instructions:
http://www.homedepot.com/p/t/1002106...specifications
make a 4" hole in the end- there should be pipe holes in the end ..top of the end is where it should be bottom of inlet should be ~5" from the top of the chamber/end.
this item will store (1.33x6.33x2.83) about 23 and a half cubic feet of water or about 175.5 gallons of water (7.48 gallons per cubic foot) each.
buy enough 4" pvc drain pipe to go from your downspouts(one or two of them) to where you are going to dig.
buy enough filter fabric to fill the bottom & sides of the hole you are about to dig.
buy~150 cubic feet of 2" gravel to surround the chambers + enough to line the drain line trench bottom
make your trench you are digging 5'wide ~3.5foot deep and 17' long to enable you to use 2 of them for groundwater recharge also make a 12" wide trench ~2' deep from the downspout location to the end of the hole. put filter fabric into recharge area bottom and sides. put 6" of stone on bottom of trench- make it level-
place both chambers into the hole according to the instructions,. centered so that there is 1' on all sides of space
fill hole with gravel- barely compacted- you want the space(voids) between the stones until you are where the invert of the pipe should be (~5" from the top of the chamber) place your pipe into the invert and run it to your downspout at a minimum 0.01 slope(pipe should go from the chamber invert up 1" per 10' section
fill main trench with stone until the chamber is covered with ~6" of gravel- you SHOULD be about 12" from the top of the hole now. fold filter fabric over gravel. fill hole with dirt
fill drain line trench with dirt.
@house connect downspout to drain. tada done.
now this is a SMALL system i have no idea how large your house is, but this system should be able to store and drain into the ground 465 gallons of water when full. if your perculation rate(rate at which the water absorbs/drains into the ground) is say 10 minutes an inch then every 10 minutes about 25 gallons of water is leaving the system.
using city of boston regulations of 1" of runoff stored and recharged, it is good for a 746 sq.ft. of roof.(31'x24') since you have a french drain and other possible factors draining your roof, this is a good system size for supplemental roof runoff storage and infiltration requirements and taking some of the roof runoff away from your foundation.