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The stormwater connection from rain to recreation 

A Harris County, Texas Stormwater Story Map 

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The Houston Advanced Research Center 

Link to Stormwater Connection Data Viewer.

Harris County is a diverse metropolitan area that includes a variety of land use types including residential, urban, industrial and undeveloped natural areas. Each type of land use has a unique interaction with stormwater (rain water plus surface water runoff) each resulting stormwater pathway represents different opportunities for stormwater management.

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The City of Houston, Texas

In the flat coastal Gulf Prairies and Marshes ecoregion, spring rains are abundant. The spring of 2015, inundated with heavy rainfall, was no exception. Average monthly rainfall for six rain gauges throughout Harris County show that from March through May, a total of 28 inches of rain was recorded. 40 inches of rainfall was recorded for the remaining nine months of the year. That means 41% of the 2015 total annual rainfall fell in just three months.

Stormwater = rain water plus surface water runoff
Harris County rain gauges

The impact of rainfall on water quality depends on the amount of rainfall, the number of days since the last rainfall, and the moisture content of the ground cover and sediment. As the number of days without rainfall increases, there is more time for pollutants to accumulate on the land in the watershed. The next heavy rainfall can wash these pollutants into creeks, bayous, lakes and rivers - known as the first flush effect.

The watershed connection

Stormwater drainage pathways 

Stormwater drainage pathways range from the natural (bayous, rivers and wetlands) to developed (channelized bayous, storm drains and stormwater Best Management Practices (BMPs)). Some stormwater pathways filter stormwater pollutants while supporting aquatic life, wildlife and recreation.

Creeks, rivers and bayous help drain the land during rainfall events and prevent flooding. These natural pathways also remove pollutants from stormwater because rain water often flows through a riparian corridor (the floodplain next to the stream) or other vegetation that provides filtration.

The pollutants carried via stormwater runoff can include pet and wildlife waste (bacteria), fertilizers and detergents (nutrients), oil and pesticides (organic toxins), trash and litter, sediment, and chemicals from commercial and industrial sites.

To storm drain 

Storm drains are installed to prevent flooding by draining stormwater from impervious surfaces such as roads, parking lots and roof tops. Storm drainage infrastructure's primary purpose is to funnel excess water away from homes and business as quickly as possible. Stormwater remains untreated and flows directly into rivers, bayous, or creeks and, ultimately, Galveston Bay.

Concrete infrastructure does not provide the filtration and infiltration that vegetated surfaces do to provide stormwater pollutant reduction.  

To wetlands

A number of pathways release stormwater into wetlands. Wetlands receive flow from stormwater outfalls and sewers, bayous and creeks as well as overland runoff. Wetlands perform vital ecosystem services, such as reducing the amount of damage caused by flooding while providing green space to recreate and revitalize. They serve as natural stormwater storage areas and provide filtration for stormwater. However, they have a limited capacity to reduce stormwater pollutants and control flooding.

Coastal wetland

The ability of wetlands to process stormwater is enhanced when the stormwater first flows through natural channels that begin reducing stormwater pollutants by allowing sediments to settle out of the water column, promoting infiltration into groundwater and serving as vegetated riparian corridors to filter nutrients and bacteria. The network of connections makes the system successful.

To natural waterways 

Houston is often referred to as the bayou city due to the large network of meandering bayous, several of which flow through the downtown district. Although some of the natural bayous such as Greens Bayou have been channelized and lined with concrete , many creeks and tributaries remain in their natural state. These natural waterways provide drainage, reduce water quality pollutants, and provide habitat for wildlife.   

Armand Bayou

The best practice to reduce impacts to water quality from stormwater and reduce pressure from increasing development is to preserve natural waterways that have intact native riparian corridors. 

Reach out to the Galveston Bay Foundation for help conserving your property.

Clear Creek

Natural waterways can help to mitigate flooding. Vegetation, soil, and wetlands have large natural storage capacities that can slow rising water levels. In addition, vegetation helps to prevent erosion and reduce water quality pollution. As surrounding land use shifts farther from pre-development conditions and the amount of impervious surface increases in a watershed, more runoff is created and less filtration and infiltration occurs.

Vegetation and living organisms found in soil can filter bacteria, sediment and nutrients from stormwater. Vegetated waterways reduce costs for drinking water plants to purify water for human consumption and provide the added bonus of supporting recreation and wildlife.

To stormwater best management practices

Stormwater Best Management Practices (BMPs) are structural and nonstructural constructed landscape features such as wet and dry bottom detention ponds, bioswales and wetland basins. To manage stormwater The Harris County Flood Control District develops, installs and maintains strategic BMPs that reduce damage caused by flood events and improve stormwater quality. It is this cumulative BMP network that creates a county-wide tool to reduce nonpoint source stormwater pollution and detain excess stormwater resulting from periods of intense rainfall.

Harris County maintains structural stormwater BMPs and a number of detention ponds that serve a growing population. Installations range from Riparian Wetland Channels and Open Water Wetland Basins to devices that control floatables (trash and debris). To supplement and support the wet bottom detention ponds, dry bottom detention ponds have been dispersed throughout the County. 

Armand Bayou Wetland Basin

Clear Creek Dry Bottom Detention Pond 

Located in the Clear Creek watershed at Dixie Farm Road this BMP features a tree lined riparian channel. The basin was designed to slow peak flow and only holds water for a short time after a rain event. In general dry basins are designed to discharge the captured stormwater at a reduced flow rate over a set amount of time, normally 24-48 hours. Fewer dry basins are being constructed in favor of wet detention basins that offer a variety of additional environmental benefits.

Clear Creek Dry Bottom Detention Pond

The primary method of bacteria removal in detention basins is settling and sedimentation. The total pollutant reduction depends on the pond length and detention period of the runoff. The period of detention also correlates with the reduction of bacteria concentrations through natural decay, thermal death, exposure to solar radiation, competition and predation. The longer the period of detention, the more bacteria are removed from stormwater.

The destination 

Be a steward of your watershed and remember that everything on the land will ultimately flow to Galveston Bay. 

Armand Bayou

Thanks to our project partners

This Story Map is part of the HARC GIS Applications collection. If you’ve enjoyed this screening, explore others in the collection including:

Texas Coastal Resource Viewer 

A Wetland Friendly Drilling Story 

Development Watershed Information Planning Tool 


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