Getting Started With Drainage Control
Drainage and erosion are a natural processes. Do not panic. Every coastal property has some degree of surface and groundwater flow. You will never be able to control these drainages entirely. So the goal of absolute drainage control is usually not technically feasible nor is it usually necessary. The practice of drainage control is really the practice of managing flows to the point where they are not contributing to accelerated erosion and landsliding along your coastal slope. Drainage and coastal erosion may be managed but not eliminated. Therefore, you must plan with them.
Surface and ground waters influence slope erosion and stability. Each year wet weather stresses many vulnerable properties to their points of failure which causes severe erosion and landsliding events around Puget Sound. These notable occurrences can usually be traced to the following issues: recent changes in the surface conditions around a property; accumulated small slope stability weaknesses that go undetected or unattended; or poor drainage system performance on a property.
You have probably observed some signs of slope distress during a wet weather season. As a coastal property owner, you should be aware of the role water plays in the short and long term stability of coastal slopes. Excessive soil erosion and land movements can create restoration costs and environmental impacts costs. Each of these costs is avoidable.
Although this website deals primarily with managing drainage issues along coastal slopes, other factors also influence slope stability and erosion of slopes. These factors include: subsurface geological characteristics; vegetation management on and above slopes; property modifications during property development; and coastal marine processes acting at the slope toe. Each of these factors should also be considered in your drainage planning to provide a comprehensive approach to slope stabilization and erosion control. Other Ecology publications are available to help with your planning. Refer to the links section for more information.
The main sections are introduced on Figure 1. Each section builds on information presented in previous sections. So, it is important that you review each section of the website before skipping directly to specific sections.
Three basic steps can protect your slope against accelerated erosion and landsliding. First, understand your property. It is not an extensive effort to generally characterize your slope area and identify the water movement around the slope.
Second, identify problems and plan appropriate improvements into your site. Take the opportunity during property development to include drainage control with your landscaping work. On each coastal property, there are typical site constraints which must be considered. Identifying the opportunities and constraints of your site are key goals of your planning effort.
Third, carefully construct and maintain your drainage system. Taking the time to ensure that good materials and workmanship are used on your property cannot be overemphasized. Give your system periodic maintenance tune-ups.
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