>> he was saying that his house never used to flood and he was blaming it on an enormous parking lot that had been constructed and the displacement of water falling on that parking lot, and how that was contributing to the stormwater issue in his neighborhood.

The hardest day’s work I ever did was soil percolation testing as a summer CivE intern. Some municipalities have a rule for new development where any rain that is expected to fall on a property must be absorbed by the property, so a percolation test (“perc test”) gives you a number you can use to figure out how much of your landscape you need to keep undeveloped in order to absorb the needed rainfall.

In the municipality I was in, a test involved digging a cylinder hole roughly a foot in diameter and a few feet deep, then periodically dumping in a painters bucket of water. You’d then record how many inches of the dumped water was absorbed every ten minutes or so over the course of the next few hours. It’s not the most scientific test: the tests don’t normalize for recent rainfall, for one, but it’s part of the rules. For the property we were testing (summer camp), me and two other people dug twelve holes throughout the property and staggered our water pours so we could walk in a loop and continuously take measurements. The kicker was that there were only two water spouts on the property to fill the buckets, so the whole day consisted of lugging water buckets up and down hills in the mosquitos and humidity so we could finish the tests.

More broadly, though, an interesting consequence of water runoff rules is that it shapes how you design a home. Since too much house meant the remaining grass isn’t considered sufficient drainage, architects are disincentivized from having any roof overhang: since the covered roof area on small lots is constrained anyway, you make more money if you put house under all of it! This is also a reason you’ll see houses with gravel driveways: gravel driveways are good for water percolation.

>> When somebody decides they want to open a new restaurant or open a new building, instead of saying it needs X number of spaces, we could say, let’s look at the parking stock and find accommodations that are already there. Office parking could be used at night for residential parking. That dentist’s office parking lot could become the parking lot for a restaurant.

If I recall correctly, the town I was working in had some limited version of this. There could be sharing between businesses whose operating hours differed considerably, but these rules were piecemeal and didn’t help a whole lot in normal situations like when several similar businesses are nearby (i.e. restaurants). In the municipality I was working in, there was a table in the regulations mapping the business type (restaurant, medical, retail, etc.) to the number of parking spaces required per unit area (not per expected occupants). You actually need *more* parking per area for a bar than you do for a restaurant, because it’s standing room.

>>The first is that many jurisdictions in this country have parking requirements for new housing. That places a geometric and financial constraint on the types of things that can be built”

These requirements aren’t just things like “you need space for two cars for this house”, but also things like “the corner between the driveway and the street must be rounded by at least a radius R”, which when combined with all of the other geometric rules about the house footprint, setbacks (distance to the edge of property you can’t build in, which themselves sometimes vary depending on what edge of the property is on a street) etc, it becomes a bit of a jigsaw puzzle.

I don’t want to keep rambling too much but I think what I’m trying to communicate is that whenever you see a parking lot or building which looks like it made with some horrible, obvious design flaws, the engineer who designed it was fully aware of there being a better alternative. By the time you apply all the federal, state, and local rules, the number of knobs an engineer can actually tune for parking or building layout are surprisingly limited. Whether you think this is a good or bad thing is up to you.