How can raise a downspout drain from ground level (Picture)

Question

I have a gutter downspout in my backyard that leads to a 4" clay drain which leads to the municipal sewer line. Currently the opening sits at ground level. I'd like to raise the ground level a few inches to provide more of a grade away from the building. How can I raise the opening such that it is a tight connection that will NOT allow earth infill to go down the drain?

In the picture, you'll note plastic adapters that connect rain gutter to drain (which would not prevent dirt/sand from going down the drain if I raised ground level).

UPDATE: Thanks for the comments. To clarify, I'm concerned that the plastic adapter (lower, yellowed plastic piece in picture) does NOT provide a tight enough connection to the drain and that it would lead to dirt/sand getting into the drain. I'm OK with the gap between the bottom of gutter downspout and the rectangular-to-round adapter (for now).

As to some comments, I'm not looking to change the grade of the pipe, but rather the grade of the soil/mulch to allow for better water runoff away from the building (water that doesn't go in the gutter/drain). Also in this neighborhood, it is a combined sewer/storm system.

Answer 1

Hopefully that downspout doesn't ultimately end up connected to the municipal [sanitary] sewer system -- my local sanitary sewer operator, and I suppose many others, bar this practice because it leads to rain flows overwhelming the sewer treatment plants, and this leads to discharge of untreated sewage.

Anyway, on to your question. That white rectangle-to-round adapter looks like an ordinary PVC downspout adapter to a 3" pipe. You could raise this by inserting a 3" coupler and short bit of pipe. These are likely available at a home improvement or building supply outlet. Some retailers might put these together with the other plumbing products; others put these drainage-related items in the sprinkler or landscape supply section instead.

Loosen the downspout from its mounting straps so that it can be lifted out of the adapter, place the coupler and piece of pipe and then re-install the adapter, and finally trim the downspout to fit the new height.