Good morning Paul...
Here are a couple of Links:
https://www.google.ca/search?q=airport+ ... 7&dpr=1.56https://en.wikipedia.org/wiki/Airfield_traffic_patternTaken from above Link:
While many airfields operate a completely standard pattern, in other cases it will be modified according to need. For example, military airfields often dispense with the crosswind and base legs, but rather fly these as circular arcs directly joining the upwind and downwind sections.
You can also read in the above Link that an aircraft landing or taking off on a Sloped Runway takes off downhill and lands uphill regardless of wind.
It also depends on the aircraft types wing...one always wants to keep the airfield in sight so a circular pattern is more appropriate for some aircraft.
Some sort of Circuit Pattern holds true for landing on water on floats or a seaplane and on frozen water (ice) at a Seaplane/Float-plane Base landing on skis or wheel/skis.
It all comes down to Safety and Keeping the Landing Area in sight.