How to Redirect Water Runoff in the Greater Seattle Area

By Frank Gaborik | April 22, 2023

How to Redirect Water Runoff in the Greater Seattle Area

redirect storm water from property

Across Seattle, water runoff has been a common concern for the city and its citizens. Some sections of the region are particularly vulnerable to flooding due to intense rain storms that overwhelm the drainage systems. Even if the heavy rains don’t lead to disaster, they can still wreak havoc on your property if your drainage is not set up efficiently.  To manage this, we will show you several options for how to redirect water runoff in Snohomish, King, and Pearce Counties. 

1. Intercept water with a French drain

A French drain is a simple trench dug at the base of a slope. This trench consists of perforated and corrugated pipe covered with a filter fabric and is usually filled with gravel and stone or soil. The fabric will filter out debris from the runoff water, while the pipe will take the filtered water to a suitable area.

This system enables rainwater to seep into the ground, flow onto a layer of gravel, and then pass through a geotextile fabric before entering the perforated pipe. 

The drain pipe is then routed downhill, away from your house and the rest of your property. The water flows freely through the pipe until it reaches a suitable outlet such as a municipal drain, natural stream, a storm overflow basin or wherever the best option your French drain professional deems worthy. The drain pipe needs the correct slope of at least a ¼ inch drop for every linear foot of length to ensure that the water is adequately drained away.

How to Redirect Water Runoff with a french drain

A properly constructed French drain should:

  • Be at least 18 inches wide
  • Have a minimum trench depth of 24 inches
  • Have a pipe with holes punched in it to allow the water to flow
  • Have a layer of geotextile fabric on top of the pipe
  • Have gravel/stone surrounding the pipe for stability

French drains help redirect water runoff to reduce the possibility of your side sewer backing up. You can guide the runoff to a mainline (municipal line) for less stress on your side sewer (you will need a permit for this). In Seattle, side sewers have been a problem for many residents. This video below goes through the Side Sewer Sagas of the Flusher family. It educates people about what to flush and the reasons for backups in your plumbing.

2. Build a Swale for gentle water redirection

A swale is a broad and shallow depression or a ditch that effectively manages stormwater runoff by directing it to a suitable outlet. This allows the water to soak into the ground while the excess runoff is routed away to another area.

a swale redirects water to a destination of your choice

To build a swale, you should start by determining the runoff path and then dig a shallow trench along it. To prevent erosion along the slope, you should use sod or other vegetation types to design the swale’s sides. The grass is very effective in preventing erosion and adds aesthetic value to the swale. Stone is preferable in areas where grass cannot grow.

If your property has a heavy flow, the stones used should be larger so they can act as stabilizers. Smaller stones can then be used as fillers. The stones should be placed in a checkerboard pattern to ensure water flows evenly across the swale.

3. Install a catch basin

A catch basin is a pre-fabricated structure with a top-slotted drain, a reservoir, and a bottom outlet pipe. It filters out debris such as leaves, twigs, and dirt from the water before it enters the outlet pipe. Most homeowners prefer installing it at the end of a driveway or the lowest spot on the property where runoff usually collects.

catch basin to collect water runoff
Image source

The concept of a catch basin is simple. The inlet allows the runoff to flow into the reservoir, while the bottom outlet pipe takes it away to an appropriate area. The reservoir is designed to hold the runoff until the water level rises to the downspout and it begins to drain away gradually. This gives the water enough time to settle and filter out so that it is clean and free of debris to prevent blockage and reaches its designated outlet.

The catch basin should be large enough to capture all of the water that is running off into it but small enough to be easily maintained.

4. Use splash blocks and downspout extensions

The splash block is a perforated platform positioned beneath the end of a downspout. It allows water to flow away from your house in a gentle sheet rather than cascading down the downspout and forming a large puddle.

Downspout extensions are also an effective tool for managing runoff. They extend the length of the downspout and direct the water away from your house, creating a path for it to follow. You can even incorporate them into your landscaping to enhance its visual appeal.

This combination of splash blocks and downspout extensions can effectively control runoff in areas with small amounts of water. It ensures that the water is dispersed evenly and away from your home.

Other Tips for Dealing With Excess Stormwater

Grow a rain garden: A rain garden is a planting bed specifically designed to absorb water runoff. It’s usually located near the base of a downspout or where water collects. To ensure that rainwater is absorbed, the soil should be amended with organic matter and a layer of mulch.

Harvest water: Collecting rainwater for use in your garden or lawn is an excellent way to conserve water and reduce runoff. You can use a rain barrel or even an underground storage tank.

Install permeable paving: Permeable pavers are installed in a grid-like pattern, allowing water to seep through them and be absorbed into the ground. This helps reduce runoff and keep water on your property.

Create detention ponds and basins: For temporary storage of excess water, you can create a detention pond or basin. These are relatively simple to construct and can be designed to fit into your landscaping. They are also effective for controlling water flow during periods of heavy rainfall.

Trust Danika Plumbing for any plumbing issues

No matter what stormwater runoff problems you’re experiencing, Danika Plumbing is here to help. We specialize in French drain design and installation and can direct you to the right solution for redirecting water runoff. Our experienced plumbers can provide a comprehensive assessment and repair any plumbing issues or install new systems to help manage stormwater effectively. 

Reach out to us if you need assistance with water runoff solutions that may be affecting your home. We look forward to helping you keep your property safe and dry.

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