Skate Ramp Modelling Issues

Hi Guys, hope your all doing good?? I am modelling a skatepark in blender and I have come to a point that I cannot figure out!
The above pictures kind of explain it, I need to create transitional curves but link them up seemlesley, how is best to draw this? Also if you can figure this out without being destructive that would be great incase I need to edit at a later date!
Thanks hugely in advance! Thanks

It looks like you might want the boolean modifier for this.

One way I can think of is that you create a solid object to cut out the hole in another mesh with the boolean modifier. I think you could use many meta balls and join them together to achieve the curved and connected crater shapes.