Drainage
Stormwater and Coastal Bluffs
Surface Runoff & Proper Drainage
All rain that falls on your property has to go somewhere. Usually, on a shorefront property, it runs into the ocean. This means all the chemicals from impervious surfaces such as roofs, driveways, roads will enter marine ecosystems unless properly filtered and managed.
Effective drainage management helps control on-site water flow and reduces the risk of erosion. Removing vegetation and adding impermeable surfaces like buildings, driveways, and patios can increase water runoff toward the bluff, raising the risk of erosion and landslides. By redirecting rainwater through drains or pipes to the toe of the bluff, you can mitigate these risks. Swales and native vegetation are often combined with drainage systems to filter runoff before it enters the piped system.
Permits are required for drainage projects that divert surface water to the beach.
Drainage Brochure
Click below to view and download our drainage management brochure.
Each of these examples will result in increased erosion and scour. Where allowed, drainage systems from bluffs should reach the toe of the bluff and incorporate a diffuser to slow the input of water to the beach.
When the land’s natural ability to soak up and slowly release water is dramatically reduced what is the result?
Faster, more concentrated flows that can overwhelm drainage systems.
Solutions
Control Excess Water
Managing runoff using rain barrels to distribute rainfall, rain gardens to clean water, diffuser tees to slow water outfall, and proper drainpipes to limit leakage ensures that marine habitats will stay healthy and erosion will be as limited as possible. A well-vegetated property using native trees and shrubs is the best solution for reducing surface flow from upland sources.
Before installing rain barrels or rain gardens, consult with shoreline experts for appropriate placement. Rain barrels should only be placed far away from the bluff crest. Rain gardens are not appropriate solutions for bluffs as they can increase infiltration to unstable geology.
Slow Outfall Water
The outfall is where runoff exits the drainage system onto the beach. Installing a t-diffuser at the correct height will reduce beach erosion by gently dispersing water.
Enhance Vegetation
Preserving existing plants and adding new, especially native vegetation, helps absorb water and stabilize both the soil and slope. Healthy plant cover is essential for maintaining slope integrity.
Minimize Impervious Surfaces
Reducing paved areas, such as driveways, and opting for building up rather than out can lower surface water runoff. This allows rainwater to soak into the ground, where plants can absorb it, reducing erosion.
Install a Drainage System
A properly designed drainage system directs water to a safe discharge point, like a beach or a stormwater storage area. This reduces the risks of landslides and surface erosion by safely managing excess water.
Use Correct Materials
Using unsuitable materials to manage drainage can lead to more harm than good. If a pipe cracks, it can direct water to a specific portion of a bluff, increasing erosion rates. Make sure installed drainage is tight, secure, and hardy. HDPE pipes are the most effective solution. PVC and corrugated pipes tend to fail in our cold PNW winters.
Resources
Stormwater and Coastal Bluffs
A guide to improving stormwater management on your property.
Winter Shoreline Reminders
Excessive rain and wind during the winter can accelerate erosion issues especially if you reside on a coastal bluff. Learn what to look for and best management practices for managing stormwater during harsh winters.
Stormwater Management in the Summer
Summertime is the perfect time to test your stormwater drainage systems to ensure they are functioning properly. Learn how to test your system for functionality here.
Identifying Drainage Routes on Your Coastal Bluff Property
Having a detailed understanding of drainage routes on your property is key for limiting erosion on your property. Learn how to identify drainage issues here.
Visualize the Warning Signs of Poor Drainage & Adaptations to Implement on Your Property
Are you a visual learner? Look here to see how typical signs of poor drainage can appear and what actions you can take to improve your system.
Managing Drainage as a Shoreline Landowner
Scroll to page 34 and beyond to better understand best drainage practices and how to safely manage it on your shoreline property.
