Stormwater Pollution: Environmental Impact And Solutions

Stormwater pollution is a pressing issue that arises when rainwater or snowmelt, instead of being absorbed into the ground, flows over impervious surfaces such as roads, parking lots, and roofs, picking up pollutants like oil, fertilizer, pesticides, and bacteria along the way. This contaminated water, known as stormwater runoff, eventually makes its way into nearby water bodies, including streams, rivers, and oceans, without the benefit of natural filtration or treatment. The impact of this pollution is twofold: it causes physical damage, such as flooding and streambank erosion, and it severely harms the environment through water pollution.

Stormwater carries pollutants like nitrogen and phosphorus into waterways

Stormwater is a significant contributor to water pollution, as it often contains harmful materials picked up when it washes over streets, parking lots, and roofs. When it rains, water runs off roofs and driveways, collecting pollutants such as fertilizer, oil, pesticides, dirt, bacteria, and other contaminants as it flows through storm drains and ditches. This untreated water eventually makes its way into streams, rivers, lakes, and oceans, causing significant ecological damage.

Nitrogen and phosphorus are primary pollutants in stormwater, and they have severe impacts on aquatic ecosystems. These nutrients, which are commonly found in fertilizers, contribute to plant and algae blooms in waterways. When excess algae grow, they produce toxins that are harmful to humans and the environment. This phenomenon, known as harmful algae blooms (HABs), poses risks to swimmers and pets, and it can also contaminate drinking water sources. Human exposure to HABs can result in skin rashes, liver and kidney damage, neurological issues, and respiratory problems.

The concentration of nitrogen and phosphorus in stormwater varies depending on land use. Residential areas, for instance, tend to have higher levels of phosphorus due to the use of fertilizers and other sources. Urban runoff, which includes contributions from agricultural fertilizers, manure, sewage, and industrial effluent, is another significant source of phosphorus in stormwater.

To address the issue of stormwater carrying nitrogen and phosphorus into waterways, several measures can be implemented. Proper waste disposal, including pet waste and litter, is essential. Additionally, reducing the use of fertilizers or switching to slow-release fertilizers can help minimize the amount of nutrients entering stormwater. Implementing green infrastructure techniques, such as rain gardens, pervious pavement, rain barrels, and green roofs, can also help slow down and filter stormwater, reducing the amount of pollutants that reach water bodies.

By understanding the sources and impacts of nitrogen and phosphorus in stormwater, we can take the necessary steps to mitigate their effects on the environment and protect the health of our waterways and ecosystems.

Impervious surfaces increase flooding and alter natural river flow patterns

Impervious surfaces are human-made features such as asphalt, concrete, and rooftops that do not allow water to pass through them. These surfaces are impervious to rainwater, which, instead of seeping into the ground, runs off into storm sewers and then quickly into local creeks, streams, and rivers. This can result in localized flooding and alter natural river flow patterns.

In natural, undeveloped environments, soil and vegetation absorb rainfall, slowing its movement into surface waterways. However, with impervious surfaces, rainfall cannot soak into the ground and instead flows across these surfaces, picking up nutrients, trash, pollutants, and sediment along its path. This leads to an increased volume and speed of water flowing into streams and rivers, altering their natural flow patterns.

The increased volume and speed of water can cause physical damage such as flooding, streambank erosion, and loss of fish habitat. The pollutants carried by the water further harm these ecosystems, impairing their ability to function properly. For example, sediment can cause cloudiness that reduces access to sunlight, oxygen, or habitat that aquatic plants and animals require.

The impact of impervious surfaces on flooding and river flow patterns is particularly significant in urban areas, where rapid development has led to a large increase in impervious surfaces. As cities expand, more land is covered by roads, buildings, parking lots, and other impervious surfaces, reducing the area available for water infiltration. This results in higher volumes of stormwater runoff that must be managed through drainage systems, leading to more frequent and severe flooding events.

To mitigate the effects of impervious surfaces on flooding and river flow patterns, it is essential to reduce the number of impervious surfaces and encourage the use of permeable materials. Implementing measures such as rain gardens, green roofs, and permeable pavers can help slow down and absorb stormwater, reducing the risk of flooding and altering natural river flow patterns.

Sewage overflows caused by stormwater can carry pathogens and toxins

Stormwater runoff can carry sewage overflow, which can contain pathogens and toxins. Sewage pollutes waterways with pathogens, excess nutrients, heavy metals, and other toxins. These pathogens can cause gastrointestinal illnesses when ingested and are usually the reason for swim advisories at public beaches. They can also end up in drinking water supplies, causing infections, hepatitis, dysentery, and other diseases. Sewage also carries excess nutrients, which can cause harmful algal blooms that pose fatal risks to swimmers and pets.

Sources of pathogens in sewage include improperly disposed pet waste, livestock manure, and failing home septic systems. Sewage overflows can occur when stormwater management systems treat precipitation as waste rather than a resource, leading to overwhelmed local infrastructure.

To prevent sewage overflows, stormwater can be managed through natural methods that mimic natural hydrologic processes, such as percolation through soil and plant uptake and transpiration. Preserving natural features, such as floodplains with vegetative buffers along streams, can also help slow down and filter stormwater.

Stormwater can destroy aquatic habitats and lower oxygen levels

Stormwater can have a devastating impact on aquatic habitats, causing physical damage and lowering oxygen levels. When too much water drains into a creek or river too quickly, it can cause flooding, streambank erosion, and the loss of fish habitats. The speed of the water also increases when natural landscapes are replaced with impervious surfaces like roads, parking lots, and roofs. This means that, in addition to the physical damage, the water also picks up more pollutants as it rushes over these surfaces.

Sediment is one of the most common pollutants found in stormwater. Soil erosion occurs when stormwater washes bare soil into streams, and this sediment can smother aquatic habitats, alter stream flow, and increase nutrients to harmful levels. This can be mitigated by covering bare soil with mulch or crop residue, which slows down stormwater and reduces its erosive energy.

Excess nutrients, particularly nitrogen and phosphorus, are also often found in stormwater. These nutrients can cause plant and algae blooms in streams and rivers, including harmful blooms that can be fatal to swimmers and pets. When the algae die, they sink to the bottom and decompose, removing oxygen from the water. This means fish and other aquatic organisms cannot survive.

The impact of stormwater on aquatic habitats and oxygen levels is a serious issue, and proper management is key to reducing these harmful effects. Green infrastructure solutions, such as permeable pavement, green roofs, and rain gardens, can help to slow down and infiltrate stormwater, reducing the amount of polluted runoff that enters water bodies.

Stormwater can carry debris that chokes, suffocates or disables aquatic life

Stormwater is water that runs off roofs and driveways and collects pollutants as it makes its way through storm drains and ditches to our streams, rivers, lakes, and oceans. Stormwater can carry debris that chokes, suffocates, or disables aquatic life.

Stormwater can pick up trash and debris as it washes across the land. This includes items that should have been disposed of in landfills or incinerated, but instead, end up in the environment where they can harm wildlife and clog stormwater systems. Sources of this trash include littering, dumping, and loose garbage set outside on windy days. This trash can then be carried by wind or water into nearby waterways, travelling downstream and ultimately ending up in the ocean. Marine debris can include plastic bags, bottles, balloons, fishing gear, and vessels.

Plastic is one of the most extensive types of marine debris, with at least 8 million tons ending up in our oceans every year. Plastics can break down into microplastics, which contribute to human and wildlife health risks as they are ingested and move through the marine food web. Plastic ingestion can lead to loss of nutrition, internal injury, intestinal blockage, starvation, and death in wildlife. Seabirds are especially vulnerable, with plastic found in 90% of seabirds.

Derelict fishing gear is another type of marine debris that poses a threat to aquatic life. Nets, ropes, and lines can entangle marine animals, leading to injury, illness, suffocation, starvation, and death. Sea turtles, in particular, are at great risk of entanglement, with over 1,000 sea turtles stranded in Florida due to entanglement in fishing gear between 1997 and 2009.

To reduce the impact of stormwater debris on aquatic life, it is important to properly dispose of waste, reduce consumer waste, and volunteer in community cleanup efforts.

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