RG wrote:
How the heck to they keep the boat ramps or the marinas available with 100
ft. drop?


In the case of ramps, you grade and pour concrete to the water's edge when
the reservoir is on the way down. When the reservoir is on the way back up,
you have a fully functional ramp. In extreme cases, a temporary cofferdam
is built to allow construction/extension of the ramp.

In the case of marinas, they all float. Everything floats. Slips, ship's
store, restaurant, fuel dock, everything. The floating marina is tethered
to the ground by cables that are attached to large winches on the floating
docks and large anchors at the bottom of the reservoir. As the reservoir
rises and falls, the cables are adjusted with the winches. In extreme
cases, the marina may need to be relocated to deeper water. In that case,
everything is moved laterally and then re-secured to the bottom. It's done
that way every day in the western reservoirs and lakes. No big deal.



It is if you are the one moving the docks and marinas.