Surveying Mountain area with Phantom 4 Pro

Hello!

Could you please tell me how to make 3D model of the mountain (standing at the bottom) fully? I mean also to include mountain SIDE details (if looking from drone perspective view, trees cover side of the mountain), do I need to set to manual mode and take photos of the side? If so, how to do it, what interval, height and camera angel?

Please have a look at attached photos, where i demonstrate the example of "lost data" when i take photos only from above and try to make 3D model of the terrain. Here Mountain side view isnt visible to drone from above, because of the hovering trees above terrain.

Sometimes I need to make 3D model of very Narrow corridor of the river. Please have a look at these photos, How is it possible to do 3D model of this corridor? Currently I am working with Hydro Power Plant developing company in Georgia and they asked me to Make 3D model of river corridor (For Intake), but I do not know how its possible with such a narrow area. This is my main goal.

Making Oblique photos is no problem... But it doesn't cover most of the part because of trees.

I dont need to MAP THE WATER, i want to create 3D model AROUND THE WATER (ROCKS and GROUND). As you can see from those photos, water occupies very small area, majority are rocks and ground.

Any ideas how to achieve it? I have Phantom 4 Pro.