From what I remember, the Bay Area doesn’t have enough porous layers to absorb water. It’s rocky ground and bedrock. You don’t need to put the sunken greenhous

From what I remember, the Bay Area doesn’t have enough porous layers to absorb water. It’s rocky ground and bedrock. You don’t need to put the sunken greenhouse at the lowest point. Layer some berms below the greenhouse on the slope — effectively form swales — and plant some things there. Another possible solution is to dig out a cistern. Here is an example from India, where much of the water is concentrated in monsoon storms. Even with such heavy rain, there are cities suffering from drought. https://youtu.be/AvV-L8MdhO4 https://youtu.be/AvV-L8MdhO4 They have two storage tanks, and the excess goes into the onsite well to recharge ground water, instead of washing into the streets, contributing to flood conditions.