Pond Leveling and Retention
Ensure that your pond base is absolutely level, using long boards and a bubble level for smaller installations. Or use a transit to check the level on larger projects.
If there is not adequate support under and on the downhill side of your pond, the weight of the water may cause the downhill slope to subside, collapsing the pond. Cut back into the slope far enough that your pond will sit entirely, or at least primarily, on soil that was already in place. Fully compact any soil moved to the front of the slope through the digging process using whatever sized heavy equipment is suitable for your project. Incorporating a few large boulders at the downhill edge of your pond placement can be an interesting focal point and provide additional security for your slope-side pond.
Series of Ponds
Constructing a series of smaller ponds cascading down your slope creates a very natural water landscape effect and helps to diminish the difficulties created by one large pond. Each smaller pond must also be level and securely located, but because the weight of the water is distributed in different locations, there will be less danger of subsoil disruption. Run your series of ponds at an angle across the slope to maximize this benefit. A series of ponds also gives you the opportunity to use one of the smaller ponds as a vegetative filter.
High Cut-Away Waterfall
Excavate your slope into one large step to create a single, dramatic, high waterfall. Cutting the slope back to form a nearly 90-degree angle from flat ground requires building a retaining wall to hold the vertical face. A rock or masonry wall can include built-in planters, and trailing plants can descend from the upper rim as well. Use lights pointing up toward your waterfall to add to its impact.
Water falling in one line from a height can be very loud, which can block traffic noises but can also disturb neighbors, especially at night. A shut-off switch or timer may help resolve any conflicts.