My back yard slopes toward my house. Below is a picture taken from my dining room to help explain things. Previous owner had a french drain installed marked by the red lines. We've had a week or so of rain and low temperatures. Everything inside the red lines toward the house is dry (reasonably dry for the amount of rainfall). However, everything outside the red lines is complete mush. Hard to walk in and impossible to cut grass.
So my question is: would it be possible or worthwhile to put another french drain further up the hill by the trees to collect water? The hill actually continues to rise about double the length you see in the picture to some more houses on top, so there is a significant amount of surface area up the hill. The hill goes up very sharply to the right of the photo due to a large sewer block.
Would even digging a simple trench at a slight diagonal angle across the tree line help at all?