Polk Soil and water conservation district
The Problem
Within an urban setting, the land is often recently disturbed and consists of homes, buildings, and infrastructure. The management within these areas can impact the components of runoff after a rain event. Sediment, minerals, heavy metals, oils, and pollution contaminate the runoff that go into storm sewers networks resulting in flooding, degraded water quality, and erosion.
Landscape Modification
Prior to European settlement, Iowa’s native prairies and savannas maintained soils with high organic matter and abundant pore space. This allowed the landscape to absorb rainfall, while shedding little runoff. Most rainfall infiltrated into the soil, where it recharged groundwater flow. Clear flows of groundwater fed and maintained Iowa’s river and lakes.
Iowa’s soil resources have been significantly altered by tillage-based agricultural practices and land development in urban areas. Consequently, less rainfall infiltrates into the landscape and more surface runoff occurs today.
Urban landscapes are dominated by impervious surfaces such as roadways, parking lots, and rooftops. Urban green spaces often feature turf grass with short roots over compacted soils. Such impervious and compacted surfaces decrease the amount of stormwater that can infiltrate into the soil, resulting in higher volumes of stormwater runoff. Stormwater carries pollutants into storm drains, which discharge directly into local streams and lakes. Urban runoff causes flashy flows that erode stream corridors and compound local flooding problems.
Runoff draining from urban areas can result in a variety of pollutants in the water. Daily activities on your property impact water quality in your watershed. Have you considered what you do that impacts water quality?
Water Quality
There are two main sources of water quality pollutants in Iowa; nonpoint and point. Point sources can be traced back to a single location of pollution and are often easy to fix. Non-point sources are harder to treat because they originate from multiple points on the landscape.
Due to the vast change in Iowa’s landscape, rain water is not able to infiltrate into the soil like it used to. This, paired with our increased heavy rains, leads to more water running quickly across the surface picking up pollutants and sediment along the way. This water is then discharged directly into our rivers, lakes, and streams.
Increased nitrogen and phosphorus in our surface waters is having a negative impact on our environment. While these nutrients are essential to many natural processes, too many can be detrimental. The negative affects are being seen on both a local and nationwide scale. Harmful algal blooms leading to fish kills and beach closures are a common site throughout the Iowa summer and increased nitrogen in our drinking water is causing health concerns. On a national scale, Iowa’s excess nutrients are contributing to the creation of a large hypoxic or “dead zone” in the Gulf of Mexico where nothing can live for portions of the year.
Along with excess nutrients, excess sediment from stormwater runoff is also having a negative impact on our water sources. Too much sediment can lead to declining aquatic species habitat by causing low visibility, decreased light penetration, and increased sediment deposition in our lakes and ponds. Harmful pollutants such as metals and bacteria can also attach to sediment particles, increasing their transport in our water systems.
Ensuring quality management practices in an urban setting is key to remove and keep out sediment and nutrients into our water!
Erosion
In an urban setting, erosion can happen on a small scale in recently disturbed soils from construction sites, little vegetation cover, pavement runoff, improper management etc.
The type of erosion most likely to happen in urban settings is water erosion. As it rains on exposed soil, the raindrop will hit soil particles and break them apart depending on the management practice. The broken soil particles are more susceptible to movement across a landscape and will erode to the lowest point on the landscape. Depending on the level of storm and amount of rain, the soil particles will travel with the water and become sediment in our storm drains and waterways. The soil will also carry along any minerals, heavy metals, or oils/grease that are attached to the particle, into the waterway and contaminate the water.
Common Urban Pollutants
Yard Fertilizers – Phosphorous in fertilizers is a leading factor in algae blooms and other water quality issues.
Dog Poop – Dog poop is very high in bacteria. Because of dogs’ meat based diet, bacteria levels are much worse than in cow, pig, and other livestock sources.
Road Salts and De-icer – In late winter and early spring these chemicals drain to our local streams increasing salinity and harming critters.
Grass Clippings – This is one of the most common urban pollutants. If grass clippings are in the street they will be washed into the storm sewer where their natural nutrients, such as phosphorous, will cause negative effects on water quality.
Soil Health
Degradation is the soil is mainly due to current changes in the landscape. Healthy soils are needed in order to obtain a beautiful landscape and yard. When the quality of these soils is degraded, more fertilizers, insecticides, herbicides, and fungicides are used. This increases the risk of excess nutrients in our waterways.
Luckily, there are many ways we can all work to fix these issues and improve our environment. Visit the “solutions” section to learn what you can do!
More than one-third of our global food supply depends on Pollinators.
To provide leadership that helps people improve, conserve, and sustain our natural resources while educating them on the importance and practicality of maintaining our environment and quality of life.
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- Saturday-Sunday: Closed
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