1.   At the back of the house the land sloped away.

2.   He parked close to where the land sloped downwards to a narrow pebble beach, and switched the engine off.

3.   In front of the farmhouse the land slopes away towards the river.

4.   The land slopes down to the sea.

5.   Since your land slopes downward toward the back, you could put in a gravity drain from the sump instead of a pump.

6.   The land slopes gently toward the riverbed.