Improper management of grades is one of the most common concerns for existing and new house lots. The resulting drainage problem can cause damage to structures, plants and human health. Water must be able to flow away from structures and be prevented from ponding (See Rain Gardens below for the exception). Principles for proper drainage include:
- Slope soil and paving away from structures.
- Slope paving to shed water to soil immediately in order to avoid water concentration.
- As much as possible, direct rainwater to soil where it can be used by plants. Grade soil to sheet flow water so that excess water flows away and does not concentrate into ditches causing erosion.
- Protect/restore soil quality to maintain its water absorbing properties. Soil can become compacted during construction. To avoid compaction, protect the soil or de-compact it when construction is complete. Small increases in organic material also exponentially increase soil’s ability to absorb and store water. Both are critical for successful plant growth.
- Avoid French drains as much as possible. Over time, French drains will clog with leaves, silt and decomposed plant material. Maintenance can be time consuming, costly and is easily overlooked. Sloping the ground surface is a better and more permanent solution. It is also easier to detect an issue with surface flow before it becomes a problem.
- For areas that cannot be sloped to drain naturally, use surface drains and pipe them to free draining areas or a rain garden.