I always had the impression, in Corona Heights, that there is a special problem with extra water in the streets when it rains. Even though there are other lowland streets, some seem higher up but are still flooded more than others. It made no sense as if the streets were defying gravity.
Recently, I stumbled upon some information about the history of the neighborhood that explained everything. At one time, water flowed eastward from Twin Peaks. It traveled down 14th and 18th through Corona Valley.
It was fresh water and not salt water that traveled down these two places that are now streets. I wonder if, at sometime, someone forgot about certain plans and design went the wrong way. I’m not saying that there is some reason to be worried about properties flooding, I’m just saying that it’s pretty easy to hydroplane when you are on your bike and it rains in Corona Heights.
In the meantime, you can find more information about the history of San Francisco’s sewers here. It also includes a great deal of information concerning the history of Corona Heights.