Slope in the backyard of a house on a hill

[Sandy T]

Hello my saviors,

I have a basic question about a slope on my backyard. My house is located on a hill (not steep, maybe 15-20 degree or so). So as you see the picture, my backyard is slightly slopped (maybe 5 degree) down from neighbor A to neighbor C. The problem I have is that the retaining wall between my backyard and C is falling, so I am thinking to remove the slope, leveling the backyard. My question is
1. Do I need to have a slope (pitch) on my backyard for drainage?
2. If so, I am thinking to have a slope down toward neighbor B (pitching toward my house). Distance from my deck to the fence of B is about 30 feet. If I am pitching toward B, what slope should I make? like 12 inches per 15 feet?

I really appreciate it if you help me solve this dilemma.
Thank you!!

 

[WorthFlorida]

As we all know water flows downhill. You cannot change the slope where your neighbors would get any run off. That wall looks like it was done long ago to correct a water drainage problem. If you level it off the rain water needs to drain somewhere, not all of it will drain into the ground. You can bury drainage pipe to get the water to drain toward the driveway.

That backyard looks almost identical to the house I grew up in on Long Island including the deck. Instead of a tree we had a power pole in the same location and the ground slope sloped to the back of the home that cause water to seep into the basement.

Helping my dad around 1960, we cut into the slope and built a small retaining wall, about 12-14” high. That greatly reduced the slope. As my father went off to work he had me dig a trench on the side of the home to get the runoff to the front of the home where it sloped to the street. It worked. Only in a severe rain events would we get water. We sold the home in 2018.

 

[Sponsor]

 

[KeylaRamos]

We live on a slope too, about 10-15 degrees, and had some drainage issues. We ended up consulting a local landscaping cambridge, and they suggested a slight slope for drainage. For your case, it might be worth reaching out to a professional in landscaping (Cambridge has some great options!). They can give you personalized advice based on your specific situation. As for the slope towards Neighbor B, it sounds like a reasonable idea, but again, getting a pro's input would be key. I pitched ours about 12 inches over 20 feet, and it worked well. But every yard is different!

 

[Treeman]

You can Google "minimum landscape grades" to learn that paved areas are 1% and turf areas are 2%. 2% is 2 feet in 100 feet - that is the minimum to make sure water flows in the intended direction. Immediately around the building the drainage slope should be more. Could you develop a swale at the end of side B and then direct the swale to a lower area, maybe the driveway that drains to the road? I've been accused of being the "corp of engineers" in developing drainage and swales around my home, which was built in a hole.

It's not rocket science. Water flows from high spot to low spot. Identify the low spot to where you want excess water to run and work from there (cut and fill). I was taught that surface drainage is the most reliable when possible, vs. underground drainage.
Look up articles on landscaping for dry basements, swales for house drainage, etc.. Tons of ideas out there.
https://www.kglandscape.com/outdoor-drainage