Drainage always has to be considered and managed in the planning of large projects, especially those with steep slopes around them.
The problems occur when said drains, within the concrete plinth, get blocked, by things like small twigs and leaves, there are a few trees around the ride!
Clearing such blockages keeps a lot of small firms in business, but you can have them back for a few more thousands of pounds every few months to manage the problem...but that is literally money down the drain, so they tend to clear them less frequently than they probably should.
Makes a change in closed season to discuss drains on the smiler instead of jetwashing and fungiciding the smiler pit.