Agency Seeks Public Comment on Alternatives to Improve the Flood Capacity of the Arroyo Colorado in Harlingen, Texas

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Texas Border Business

The United States Section of the International Boundary and Water Commission (USIBWC) provides Notice of Availability and solicits public comment on a draft Environmental Assessment (EA) that presents alternative methods to restore the capacity of the Arroyo Colorado in Harlingen, Texas to carry floodwaters.  The draft EA presents alternatives to restore the capacity of the Arroyo Colorado over a 6.3-mile segment from Business 77 (Sunshine Strip) to Highway 574 (Cemetery Road) in Harlingen and Cameron County, Texas.  The USIBWC has identified the Expanded Vegetation and Sediment Removal Alternative as the Preferred Alternative to restore the full flood capacity. 

USIBWC oversees the Lower Rio Grande Flood Control Project (LRGFCP), which controls floodwater in the Lower Rio Grande and interior floodways in the tri-county region (Hidalgo, Cameron, and Willacy Counties). During river flooding, Anzalduas Dam south of Mission, Texas is used to divert floodwater from the Rio Grande into the interior floodway system to control flooding along the river. A portion of this water eventually flows into the Arroyo Colorado, a natural channel confined by high banks in most areas. The USIBWC maintains the LRGFCP and its levee systems and removes obstructions from the floodways to maintain conveyance capacity.  

USIBWC is considering additional maintenance activities that are intended to restore the Arroyo Colorado’s flood conveyance capabilities.  The Arroyo Colorado is an important part of the LRGFCP that protects residents, businesses, and farmland from flooding in the Lower Rio Grande Valley of Texas. 

Over time, increases in vegetation and sediment caused the Arroyo Colorado to lose more than 50 percent of its capacity to carry floodwaters, which increases flood risk. Recent removal of vegetation and sediment has restored some of the Arroyo Colorado’s flood conveyance capacity. 

USIBWC is considering the following alternatives, some of which would restore the full design capacity of the Arroyo Colorado:

No Action Alternative

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Current vegetation and minor sediment maintenance operations would continue. Between Business 77 (Sunshine Strip) and FM 509, vegetation maintenance occurs on 53 acres of floodplain and minor sediment maintenance occurs near bridges and other structures. These maintenance operations would continue as part of each of the alternatives currently under consideration. This alternative would not restore the Arroyo Colorado’s flood conveyance capacity, and properties in Harlingen would continue to have an increased flood risk.

Off-Channel Storage Alternative

The Arroyo Colorado’s flood conveyance capacity would not be restored. Water surface elevations would be managed by temporarily storing floodwater in a new detention basin that may require up to 2,204 acres to construct and operate. Properties in Harlingen would have a much-reduced flood risk.

Expanded Vegetation Removal Alternative

Additional flood conveyance capacity would be restored by expanding vegetation removal and maintenance activities downstream to Cemetery Road. This may not fully restore the Arroyo Colorado’s flood conveyance capacity and some increased flood risk may continue.

Expanded Vegetation and Sediment Removal Alternative

Flood conveyance capacity would be fully restored through dredging and expanded vegetation management between Business 77 (Sunshine Strip) and Cemetery Road. This alternative would provide properties in Harlingen with the greatest decrease in flood risk.

The draft EA includes analysis of what impacts this action would have on the environment, including wildlife, cultural and water resources, land use, community resources, and environmental health and justice. The draft EA is available on the USIBWC website at http://www.ibwc.gov/EMD/EIS_EA_Public_Comment.html.  The Notice of Availability of the Final Environmental Assessment (EA) is expected to be published in the Federal Register on Friday, August 14.  Public comments on this draft EA are due by July 24, 2020 and should be submitted to Mr. Kelly Blough, Environmental Protection Specialist, via email at [email protected] or via mail at International Boundary and Water Commission, 4191 N Mesa Street, El Paso TX 79902.

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