Tex: You’ve spotted a lot of the major factors involved in deciding where and how roads are built. Drains, while a very old concept (Wikipedia), can sometimes be disregarded due to budgetary concerns.
Climate is an interesting aspect, partially because our understanding of climate and how it impacts our infrastructure, has only grown over time due to a lot of research and funding being concentrated on it as politics dictate. The usage of a grid plan (Wikipedia) typically indicates a planned city, which contrasts organically-settled areas that usually follow trade and water routes.
A lot of your worldbuilding will depend on the source cultures and eras that you’re drawing from. For example, how the Iroquois League develop the land in what’s now known as New York in 1500 will differ from how the Dutch settled colonies in the 1600s, which will look entirely different to how a construction company will decide where to put new apartment buildings in the 2020s.
It’s still the exact same area, but the different time periods and whomever is the majority culture will dictate completely different perspectives on what’s important in terms of permanent vs temporary infrastructures. This can come across as polar opposites, which may seem contradictory outside the context of local history.
In terms of changing climate, that’s as much a function of history as it is technology. Yes, some old roads might flood, but some also might not, and that’s entirely dependent on contemporary meteorological patterns, anticipated changes, and how much effort was expended to effectively “future-proof” said roads.
A lot of that will invariably come down to politics, because that’s where the funds will typically come from - if it’s an important road to an area, in terms of high throughput in trade or politically important people/places, then more resources will be expended to make a sturdier road that will anticipate even unlikely scenarios, such as flooding in an area that typically doesn’t flood.
Drainage has more benefits than just flood mitigation, however - it also helps keep a road or street cleaner, by making it easier for debris to be washed away from the road. This can help reduce the amount of traffic accidents caused by mud or even snow, as well as any detritus that can be swept up by heavy rain, such as loose vegetation.
I think examining your sources and seeing their geographical context might help clear up how they approached settlements and development of their cities and towns, as well as the time periods you’ve selected for how they typically decided to allocate resources like finances and manpower. I’ll list some extra links that should be helpful, although admittedly some of them can be US-centric.
Further Reading