Urban storm water poses threat to creeks, rivers

The Tarrant Regional Water District’s Fort Worth campus demonstrates eight major green stormwater mitigation methods, including a bioswale, a raingarden, rainwater cisterns, permeable surfaces and a stormwater wetland. Courtesy of TRWD.

May 25, 2021

 

Read the original: https://greensourcedfw.org/articles/urban-storm-water-poses-threat-creeks-rivers

If you just checked the forecast to see yet another rainy weekend ahead, you won’t be surprised to hear that May, on average, is the wettest month in North Texas.

With the deluge comes rainwater piling up on streets and rushing down storm drains. It’s all going back to our creeks and rivers  – unfortunately taking urban pollution with it.

So what can we do about it?

WATERSHED MOMENT

You’ve heard the term watershed – but what does it mean?

According to the National Oceanic and Atmospheric Administration, it’s a land area that that channels rainfall and snowmelt to creeks, streams and rivers, and eventually to outflow points such as reservoirs, bays and the ocean.

Everyone lives in a watershed.

And unabsorbed water — whether it drips into the driveway, flows to the gutter or caresses the leaves of a creek-side tree — must go in one direction or another, choosing one route or another, obeying its own Continental Divide.

In North Texas, all smaller streams run to the Trinity River. A simple zip code search will reveal your watershed at Texas Parks and Wildlife’s Texas Watershed Viewer.

In rural areas, two-thirds of precipitation is absorbed into the soil. Only one-third flows into creeks or rivers.

But in urban areas, the watershed is lined with impervious surfaces like pavement and roofs, which take up half to 70 percent.

That means, water flows across concrete surfaces, down gutters into storm drains. The storm sewers mostly empty into the closest stream. The water laden with pollutants and litter rushes in at high velocity.

More precipitation ends up in creeks than they can handle. The rapid runoff scours the banks, tearing away stabilizing plant cover. Roots of riparian trees on ground level get exposed. Erosion undercuts the banks, creating overhangs that give trees little support. The trees topple, taking much of the bank with them. Surging stormwaters downcut the channel, eroding the creek deeper with every big storm.

More precipitation ends up in creeks than they can handle. The rapid runoff scours the banks, tearing away stabilizing plant cover.

Unable to reach the floodplain except in the most catastrophic floods, water has no choice but to remain trapped in the channel. The increased amount of constrained water rushes with even greater velocity, making floods downstream more likely. The vigor of creek-side trees diminishes, reducing bank integrity. Collapsed banks, scoured creek bottoms, and diminished riparian cover cause water to become loaded with sediment.

POLLUTION ON THE RUN

As rainwater or meltwater flows across impervious surfaces, it sweeps up nonpoint-source pollution like hydrocarbons and nitrogen oxides deposited by exhaust onto the paved surfaces, or air pollution that settles onto roads and roofs. Tires and brake pads leave behind polluting debris.

A ubiquitous pollutant in urban waters is Escherichia coli (abbreviated as E. coli), a type of bacteria found in people and animals’ stool. Some strains in excess can cause serious illness in humans. Stormwater moves feces from pets, livestock and wildlife and leaks from sewer pipes, many caused by creek erosion, into storm sewers and creeks.

Runoff loaded with these nonpoint-source pollutants rushes at high velocity across impervious surfaces into storm sewers and then into creeks.

Also carried along is an astounding amount of litter. An ugly line of debris often shows how high the water has risen in a stream. Litter clogs water intake devices at water purification plants and interferes with aquatic wildlife and waterfowl.

WHAT YOU CAN DO

Creek and stormwater management is shifting from a focus on water-shedding — moving stormwater downstream as swiftly as possible — to water-catching — catching and retaining water for slow and prolonged release. North Central Texas Council Of Governments offers Integrated Stormwater Management guidelines to assist cities.

Creek and stormwater management is shifting from a focus on water-shedding — moving stormwater downstream as swiftly as possible — to water-catching — catching and retaining water for slow and prolonged release.

Tarrant Regional Water District devised a 175-page Water Quality Guidance Manual for developers and landowners flanking the Clear and West Forks in Fort Worth. It provides a methodology so that discharges into the forks within a defined area of stormwater sensitivity adhere to TRWD standards. The free manual educates on best practices in green infrastructure and includes resources to aid compliance. TRWD’s Fort Worth campus demonstrates eight major green stormwater infrastructure components, including a bioswale, a raingarden, five different turf grasses, rainwater cisterns, permeable surfaces and a re-designed stormwater wetland.

Tarrant Regional Water District’s Fort Worth campus features eight major components to divert and collect stormwater.

What’s a good environmental citizen to do to improve the health of urban creeks? Here are some tips:

Slow Stormwater Passage 

•  Install more garden beds and groundcovers, use less sod. Taller plants have deeper roots and absorb more water. Thick foliage slows rainfall, enabling the ground to take in more water.

• Go tall. Allow your lawn grass to grow as tall as municipal regulations allow. Use a mulching lawnmower so that fine grass clippings return to the soil, acting as a natural fertilizer.

• Consider a native grass lawn. Buffalo grass and blue grama grow only a few inches tall and don’t have to be mowed. They require less water and no fertilizer.

• Collect rainwater. Use it for lawn and gardens, while reducing the load on storm sewers.

• Use permeable materials. For walkways and driveways, instead of concrete and pavers, use materials such as decomposed granite, which allow water to pass through.

• Let it drip. Instead of roof downspouts that force water onto lawns, use diffuser chains or allow precipitation to drip off eaves into ground cover.

• Install a rain garden. Create a landscaped basin area that collects rainwater and allows it to soak into the ground. These miniature wetlands attract wildlife, especially amphibians, while slowing runoff and filtering out pollutants and excess fertilizer.

Keep Pollutants from Streams 

• Don’t dump. Nothing should go into storm sewers except water. Anything disposed into it goes right into the creeks. In many cities, violations result in stiff fines.

• Grow organic! Most organic gardening supplements are less water-soluble than their synthetic counterparts.

• Apply lawn chemicals properly. Synthetic fertilizer tends to be over applied. Avoid applying just before rains. Instead, apply and water in gently.

• Scoop the poop. Pick up your pet’s poo and flush or dispose of with household waste. Dog and cat waste is not a good fertilizer and adds E.coli into the creek.

• Properly dispose household hazardous waste. This includes paints and thinners, drain cleaners, automotive fluids and pool chemicals. Look for specialized centers or collection drives.

• Check pool rules. Conventional swimming pool water contains chlorine, phosphates, nitrogen and a variety of mineral salts. If local regulations permit, drain into the sanitary sewer. If not, before releasing into the storm sewer de-chlorinate the water and lower phosphates to at least 200 ppb. Consider switching to an ozone purification system that reduces the need for pool chemicals by up to 90 percent.

• Properly dispose over-the-counter or prescription pills. Don’t flush or rinse down the drain. They are difficult to clear from drinking water sources. Go to TakeBackDay.dea.gov and find a disposal site or drive near you.

Help Storm Sewers Run Smoothly 

• Keep grass clippings and leaves in your yard. Don’t sweep them into the street where they can be washed down and clog storm sewers. The organic matter carries lawn chemicals into creeks and lakes as well as fertilizers that lead to algal blooms. Using a leaf blower to blow yard waste into the street can incur a hefty fine in many cities.

• Minimize dirt erosion. Exposed topsoil washed away by rain can accumulate in storm sewers. Cover with plants or erosion mats.

• Report clogged storm sewers. If you notice water not draining efficiently into the sewer, contact the city water department.

• Watch that grease! Search for the Cease the Grease program near you to find out why fats, oils and grease (FOG) should not go down the drain and where you can take collected FOG. The City of Dallas transforms cooking oil into methane to create electricity and heat for the Southside Wastewater Treatment Plant. The North Central Texas Council of Governments operates a regional cooking-oil recycling program.

Take a Load off Sewers 

• Fight the FOG. Again —  don’t pour fats, oils or grease down the drain. They harden into “fatbergs” and cause sanitary sewer pipes to clog, pushing raw sewage into your home, lawn and neighborhood. It can flow from there to rivers and reservoirs, impacting our drinking water. Running hot water at the same time or adding dish soap won’t prevent clogs in your house plumbing or community pipes. Sending FOG through the garbage disposal doesn’t help either. Collect FOG and dispose of properly.

• Don’t flush wipes. Sanitary and cleaning wipes don’t break down in water like toilet tissue. They accumulate in wastewater pipes, causing clogs, back-ups, and overflows. Throw wipes into the trash. The same with paper towels and feminine hygiene products.

• Just because you can flush it doesn’t mean you should. Cotton balls and swabs, dental floss and picks and other personal hygiene items don’t belong in the toilet, nor do condoms.

Steward Your Park 

• Form a friends group of volunteers for your local park. Propose bringing in more native plants to support pollinators and wildlife. Your local naturalist and native plant groups can help.

• Create support for reduced mowing in the park. Taller plants grow deeper root systems that slow and absorb more storm water.

• Encourage wider riparian areas with thick plant cover. Promote soft-surface trails instead of concrete.

Steward Your Creek  If you’re lucky enough to live on a creek, you’ve got special responsibilities. You are a watershed steward!

• Allow 5 to 10 yards of tall foliage to flank the creek. Native plants with deep roots work best.

• Slow erosion. Do you have bare soil or rocks? Consider installing erosion-control mats and rolls of geotextiles made of biodegradable or natural coir fibers that collect dirt while allowing water to pass through.


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