When the River Runs Muddy

This winter brought much needed rain to the Pedlar River watershed. With rain comes runoff, and with runoff comes sediment. Sediment is the fancy word for the loose sand, clay, silt and other soil particles that are dislodged from the land by rainwater and transported by stormwater runoff towards bodies of water. While runoff and erosion are natural processes, human activities on the land can drastically increase the rate at which sediment enters our waterways, making sediment pollution the #1 type of water pollution in our region of the James River watershed. (State of the James Report Card 2021, James River Association).

Our local waterways have been looking cloudy after the big rains this winter. Sediment is what makes that cloud in the water.  The color of that cloud varies depending on what kind rock, soil, and clay runs off the land or makes up the stream bottom and sides. In the Pedlar River, the sedimentation cloud often looks orange, like our clay soils.

Where Horseley Creek enters the Pedlar River, Pedlar Mills, January 2023

Activities that expose soil are the main causes of sediment pollution in the Pedlar River watershed–such as logging, removing trees and shrubs from steep slopes and near streams, farming practices such as tilling, use of pesticides and fertilizers near streams, unprotected streambanks in fields and livestock pastures, and construction practices that do not follow Best Management Practice guidelines.

Here’s the quick dirt on why we need soil to stay on the ground and out of the water, plus info about how you can make sure your property keeps its sediment to itself. Please, read on and do your part to protect our streams and rivers.

Sediment is considered a pollutant because it degrades the quality of water for drinking, wildlife and the land surrounding streams in the following ways:

It clouds the water, preventing animals from seeing food and harming aquatic vegetation.

In streams, sediment disrupts the natural food chain by destroying the habitat where the smallest stream organisms live–organisms that are food for fish.

And sediment can clog fish gills, reducing resistance to disease, lowering growth rates, and affecting fish egg and larvae development.

Sediment increases the cost of treating drinking water and can result in odor and taste problems. It fills up storm drains and catch basins to carry water away from roads and homes, which increases the potential for flooding.

Nutrients transported by sediment can activate blue-green algae that release toxins and can make swimmers sick.

(adapted from the Environmental Protection Agency’s “What is Sediment Pollution?” brochure)

And here’s more about the problem of sediment pollution:

Sediment pollution harms aquatic life by increasing turbidity (cloudiness). Sediment suspended in the water blocks light from reaching through, and this lack of light can interfere with fish as they feed and school. Lack of light also slows or stops the growth of aquatic plants, an impact that can be felt throughout the food web. For instance, organisms that live in the water need the oxygen and food aquatic plants provide, and many fish need underwater plants to protect their eggs and provide shelter for their young.

Sediment can also dislodge plants, invertebrates, and insects in the stream bed. This affects the food source of fish, and can result in smaller and fewer fish. As sediment particles settle on the bottom, they can bury and suffocate fish eggs.

Sediment particles in the water absorb warmth from the sun and thus increase water temperature. Warmer water carries less oxygen, which can stress some species of fish; warm water can also encourage overgrowth of algae, leading to eutrophication that can kill fish and other organisms.

Sediment particles can carry other kinds of pollution to the water. Pollutants such as nutrients, heavy metals, toxic chemicals, bacteria, and pathogens can adhere to sediment particles. This means they hitch a ride on sediment, which carries them into streams and rivers via stormwater runoff. Some pollutants may dissolve into the water and wash downstream quickly, while others may remain stuck to sediment on the bottom of the stream bed and cause problems for years.

Sediment carrying fertilizers from farms and yards brings excess nitrogen into waterways, which can cause eutrophication from excess algae growth, which kills fish and aquatic organisms.

AND sediment is a problem for Brook Trout who live in our watershed: Sedimentation and Brook Trout: Riparian Remedies (DWR website)

It’s not just the temperature of the water that’s so important to brook trout; it’s also the quality of the water and the composition of the streambed. According to DWR’s Wild Trout Management Plan, “Wild trout require ‘pea-sized’ gravel substrate free of fine sediments to reproduce. Sediment can also reduce habitat complexity vital for different life stages of wild trout. In addition, sedimentation can also negatively affect stream macroinvertebrate populations, which are a valuable food source for wild trout.” Severe storms and heavy rain events, which are increasing in frequency, cause both the erosion of streambanks, sending a cascade of sedimentation into the water, and increased velocity of stream flows, which can disrupt fish spawning or displace eggs. Protection and restoration projects of stream and river banks (also known as riparian areas) can help reduce sedimentation in wild trout streams. Sediment is also a pollution carrier, harming not just aquatic organisms but also our drinking water. Sediment pollution can alter water quality, stormwater infrastructures, and water ecosystems.  Excessive amounts of sediment may clog storm drains and cause flooding. Drinking water contaminated with sediment is more expensive to treat. Nutrients carried by sediment into the water may accelerate the growth of blue-green algae that release toxins and affect humans and wildlife health. (excerpted from an article about what sediment means for Brook Trout. See the entire article here: Department of Wildlife Resources in Virginia (DWR website)

Here’s how you can prevent sediment pollution at home:

Pick up your pet’s waste.  Pet waste is rich in nitrogen.  When it rains, sediment carrying these nutrients may pollute stormwater.

Sweep sidewalks and driveways instead of hosing them off. Washing these areas results in sediment and other pollutants running off into streams, rivers, and lakes.

Landscape your yard so that it encourages rainwater to slow down and sink in rather than speed up and run off.  For instance, establish rain gardens at the base of downspouts and use shrubs, mulch, and plants taller and thicker than grass next to pavement and in any sloped areas.

Keep storm drains clear and never sweep grass clippings or leaves into storm drains. Leaves and yard clippings left on the street will wash into storm drains.  As they decompose in the water, they will contribute to nutrient pollution and may cause eutrophication (toxic algal blooms).

Reduce the amount of fertilizers you use, and do not apply fertilizer right before it rains.  Limit or stop all use of fertilizers in your lawn or garden. Make sure you follow the application instructions on the fertilizer container to ensure you are not overusing the fertilizers. Check the weather before you apply it, or your fertilizer may become polluted runoff instead of food for your plants.

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