The second image in the article (Short Ferry) is, as you might guess from the name, pretty close to a river.

https://maps.app.goo.gl/iAWJmgKkApxCY7Q36

The river close to it (Barlings Eau) isn’t a “main” river. The larger one to the south west (Witham) is. The green island area between the two (to the south) is intentionally flooded when water levels get high. The whole area is pretty prone to flooding, so the fact they’re saying the scheme only pays out if you’re close to a main river is odd.

Central government (Environment Agency) looks after the main rivers, most of the others in low lying areas are maintained by local authorities (Internal Drainage Boards), who don’t get a huge amount of funding (and often have to deal with issues caused by the Environment Agency)

*aeroplane

On the class/path a: it depends where you are in the UK. In the north, it tends to be the flat a, in the south it tends to be the broad a. There’s a lot of variation in accent within the UK, to the point that you can identify pretty accurately where someone is from using something this quiz: https://www.nytimes.com/interactive/2019/02/15/upshot/british-irish-dialect-quiz.html.

Anecdotally, I think it is becoming a bit more uniform than it used to be, due to people moving around more than they did historically, though