If you’ve ever lived in an area with large flat surfaces, you’ll notice that surface runoff quickly begins to pool when it rains.
Parking lots, roofs, driveways, sidewalks, etc. provide very few places for water to go.
Surface runoff is now a leading contributor to water quality pollution, and for this reason, it’s worth paying attention to.
As a landowner, how can you address this issue?
It’s something that ultimately lies in the control of Mother Nature, but has some mitigating factors.
Here’s what you should know.
1. What is surface runoff?
Surface runoff — also known as stormwater runoff or overland flow — is water flowing on the ground surface when excess rainwater, stormwater, meltwater, or other sources can no longer infiltrate into the soil.
Surface water often occurs because impervious areas are blocking water from soaking into the ground.
Examples of impervious surfaces include roofs and pavement.
Surface water is a major component of the water cycle.
It can occur through either natural or manmade processes.
It’s also the primary agent of soil erosion by water.
Surface runoff can be harmful due to pollution.
Manmade contaminants can be picked up by surface runoff and pollute water sources.
These contaminants include petroleum, pesticides, fertilizers, etc.
So, in addition to all the other issues that can come with water (think property damage, mold, flooding), there’s the added component of pollution if surface runoff is not properly directed.
2. How is surface runoff generated?
Surface runoff is defined as precipitation first and foremost.
It originates from rain, snow, sleet, or hail that reaches a surface stream without ever passing below the land surface or soil first.
Surface runoff is different from direct runoff.
Direct runoff is that which reaches surface streams immediately after rainfall or snow melts.
Direct runoff excludes runoff generated by the melting of snowpack or glaciers.
3. What are the meteorological factors affecting runoff?
Type of precipitation (rain, snow, sleet, etc.)
Distribution of rainfall over the drainage basin
The direction of storm movement
Precipitation that occurred earlier and resulting soil moisture
Other meteorological and climatic conditions that affect evapotranspiration (i.e.., temperature, wind, relative humidity, and season)
4. What are the physical characteristics affecting runoff?
Topography, especially the slope of the land
Drainage network patterns
Ponds, lakes, reservoirs, sinks, etc. in the basin, which prevent or delay runoff from continuing downstream
5. How does human influence affect surface runoff?
Humans have drastically changed how the Earth’s landscape looks.
Urbanization has increased surface runoff because it has created more impervious surfaces like pavement and buildings that don’t allow percolation of the water down through the soil to the aquifer.
In this scenario, water is forced directly into streams or stormwater runoff drains.
Even if flooding isn’t a big issue, both erosion and siltation can be.
When there is increased runoff, groundwater recharge is reduced.
The water table is also lower, and droughts are worse.
If you depend on a water well, then you’re more likely to be impacted by this.
Humans also pollute the water supply indirectly by using various contaminants.
These contaminants (such as pesticides) get picked up by surface runoff and then carried to streams, rivers, lakes, estuaries, and oceans with resultant water chemistry changes to these water systems and their related ecosystems.
In 2009, urban stormwater was identified as the leading source of water quality problems in the United States.
6. Why can surface runoff be a problem?
Here are the core reasons why surface runoff presents a problem to the environment as well as humans.
Large volumes can overwhelm storm drains and cause localized flooding
Runoff gathers sediment and pollutants, which can end up in natural waterways
Water that doesn’t soak into soil can’t recharge local groundwater sources
7. What can happen to your property if surface runoff and stormwater runoff get out of control?
Sometimes people write off surface runoff as an issue that the government needs to deal with.
However, landowners often run into issues with runoff on their property.
Here are the issues you could see if you don’t address them head-on.
When heavy rain occurs, the land often can’t soak it all in.
This causes water to pool on the ground and run off hard surfaces.
You may see property damage when this occurs because of flooding, erosion, and property damage.
Water can become polluted as it runs across lawns, driveways, and other hard surfaces.
Even if these surfaces look clean, they collect oil, gas, fertilizers, pet waste, and other substances that you wouldn’t want in the water.
These contaminants will eventually end up in streams, lakes, rivers, wetlands, and marine waters when surface waters runs into them.
Water contamination can prompt the need for beach closures.
Bacteria, viruses, and other pathogens from pet and livestock wastes cause harm to pets and wildlife.
Additionally, failed septic systems can close beaches for swimming altogether.
If you have a waterfront property, this is something to keep in mind.
You want to make sure that your water is safe to use (for drinking, swimming, etc.), and your surface runoff can prevent this.
Increased algal growth
If there’s nutrient pollution in surface runoff (often occurring from livestock manure, croplands, landscape runoff, and failing septic systems), then this can cause excessive algal growth.
When algae die and decompose, they consume dissolved oxygen in the water.
This harms fish and other organisms who rely on it.
If you have water on your property, surface runoff could cause clouded water.
Sediment (loose soil) can cause turbidity (cloudiness) in water.
This reduces the amount of light that penetrates the water and also inhibits the growth of aquatic plants that fish and shellfish depend on.
It can also clog up the gravel in streambeds that salmon use to lay their eggs in.
If you’re struggling with turbidity, consider where sediment could be entering your surface runoff from.
It commonly occurs in construction sites, eroding stream banks, agricultural fields, and other disturbed areas.
8. What are the forms of mitigation for surface runoff?
To treat the impacts of surface runoff, the following four methods are used.
Land use development controls
This technique is aimed at minimizing impervious surfaces in urban areas.
Unnecessary hardscape can often prompt unnecessary surface runoff.
As a result, many municipalities have started to produce guidelines and codes for land developers to encourage minimum width sidewalks, the use of pavers set in the earth for driveways and walkways, and other design techniques that allow maximum water infiltration in urban settings.
This technique is primarily used on farms and construction sites.
Erosion controls have been practiced by farmers since medieval times.
However, since in the 1950s, these methods have become increasingly more sophisticated.
Flood control and retrofit programs
This technique is used when creating green infrastructure.
These programs have been useful in predicting peak flows of riverine systems.
Now, strategies have been developed to minimize peak flows and reduce channel velocities.
Examples of flood control include using ponds to buffer riverine peak flows, using energy dissipators in channels to reduce stream velocity, and maximizing land use controls to minimize runoff.
Chemical use and handling controls
This technique is used in agriculture, landscape maintenance, industrial use, etc.
States and cities have become more vigilant in controlling the containment and storage of toxic chemicals, thus preventing releases and leakage.
Here are some methods that are commonly used to prevent pollution and contain chemicals.
- Requirements for double containment of underground storage tanks
- Registration of hazardous materials usage
- Reduction in the number of permitted pesticides
- More stringent regulation of fertilizers and herbicides in landscape maintenance
9. How can you ensure surface runoff is managed properly?
There are two goals for managing stormwater runoff.
Decreasing the volume of runoff
Minimizing the pollutants in the runoff
The EPA has a mantra for surface water management.
It goes “Slow it down, spread it out, soak it in.”
As a property owner, you must manage your own surface runoff.
We recommend you do this before local ordinances demand compliance; otherwise, you’ll likely need to repair some sort of damage.
Here are a few affordable, doable solutions that allow you to do just that.
Plants are an ideal way to correct some excess runoff.
The goal is to have as much water as possible soaking into the soil, and plant roots help to absorb and filter out pollutants.
When runoff soaks into and percolates through the soil, the soil itself acts as a filter and removes some pollutants.
This is beneficial for the environment.
Incorporate plants as much as possible in your landscaping as a homeowner or landowner.
Just like smaller plants, trees help to absorb and filter runoff.
Tree canopies also slow rainfall and allow it to spread over a larger area.
This can prevent water from pooling on the ground and causing erosion.
Break up slabs
Impervious surfaces like concrete patio slabs can be a big cause of surface runoff.
Consider replacing any slabs of concrete you have with pavers, flagstones, or breaks that allow the water to soak in between items.
If you need a solution for your driveway, then a turf block is one consideration.
You could also leave a strip of grass up the center of the concrete.
This will allow some water to soak into the ground instead of running off.
There are permeable materials that you can use for paths, patios, and driveways.
Less expensive options include aggregate base, gravel, mulch, and crushed shells.
If you have more money to spend, you could consider looking at pervious concrete or asphalt.
Install a rain barrel or cistern to catch any stormwater that drains from your roof.
You can reuse this water to irrigate your garden plants.
Divert water with a trench
If you have water runoff in a specific area, you can consider digging a trench.
This solution often works well in a spot like a driveway.
Use a shallow, gravel-filled trench to catch and slow runoff at the base of a slope or alongside a driveway or patio.
For slopes, consider creating a dry creek to catch, slow down, or redirect runoff.
A rain garden (see next section) is a great option.
Plant a rain garden
A rain garden is a spot that’s designed to catch and slow runoff.
It’s frequently planted in low areas at the base of a slope or near downspout outlets.
The design includes soil layers, mulch, and plants, which helps to filter rainwater as its seeps into the soil.
Sometimes the type of soil can inhibit water permeation.
If you cover bare soil with mulch or ground cover, it can help to slow surface runoff and allow the water time to soak into it.
Swap lawn for native plants
When you integrate native plants into your landscape, you benefit because they are adapted to local growing conditions and require less attention than grass.
Drive on the grass
Okay not actually.
However, if you want to wash your car, then consider doing it on the lawn instead of the driveway.
This way, the water can soak into the soil instead of running into the street.
10. How can you landscape for water quality?
You can do a lot right and still have issues with stormwater runoff.
However, one of the most inconvenient impacts of runoff is water contamination.
Here’s how you can do your part in reducing pollution on your land.
Apply fertilizers and pesticides sparingly and do not apply before rain events
Test soil first to determine fertilization needs
Reduce bacteria by picking up after your pets and disposing of their waste properly
Wash your car on your lawn where the chemicals and soap can be absorbed and filtered by the soil instead of washing indirectly into a stream
Dispose of lawn clippings in a compost pile
Harvest and reuse rainwater via rain gardens, rain barrels, and cisterns
Preserve and plant trees
Maintain your septic tank
Surface runoff can be damaging if it’s not addressed.
Make sure you do your part on your land and around the community!
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Disclaimer: we are not lawyers, accountants or financial advisors and the information in this article is for informational purposes only. This article is based on our own research and experience and we do our best to keep it accurate and up-to-date, but it may contain errors. Please be sure to consult a legal or financial professional before making any investment decisions.