Our Back Yard, When It Rains A Lot

Our back yard doesn't look like much, but it's dry... except during/after rainstorms severe enough that it runs down from the convervation land adjoining on one side.  It doesn't happen often -- we lived here at least a year or two before the first occurrence.  This past weekend's was the biggest we've seen to date.  (But no, this wasn't what caused the problem on the MBTA's Riverside Green Line.)

Here's a few pics:

and here's a sub-minute video: