L575 Levee Restoration
Location: Hamburg, IA
Project Type: Shoreline & Waterways
Application: Levee Stabilization
Product Used: ARMORMAX
In March 2019, heavy snowfall and frigid temperatures in the Midwest were followed by what meteorologists call a bomb cyclone. This phenomenon occurs when the air near the Earth’s surface rises quickly, triggering a sudden drop in barometric pressure – at least 24 millibars within 24 hours. In three days, the temperature rose 60 degrees. This increased temperature combined with 1.5-3 inches of rainfall caused rapid melt.
The frozen ground conditions could not absorb the moisture, sending massive amounts of runoff into streams and rivers. On March 14 the Spencer Dam collapsed on the Niobrara River sending more unregulated water downstream. The Missouri River gauge at Brownville set a new record of 45.7 feet, 1 foot higher than the previous record. During this flood event, the L550 Missouri River Left Bank Levee System experienced significant damage that led to seven breaches and other substantial damage throughout the levee system. Levee breaches caused major flooding of farms and towns along the river.
The United States Army Corps of Engineers (USACE) Omaha District needed to restore the levee to it pre-flood condition, ensuring that it would be armored against future flooding. To protect the levee against the erosion-causing hydraulic forces of storm surge, the USACE used ARMORMAX®. The system is composed of Engineered Earth Anchors that are designed and tested for compatibility and performance with High Performance Turf Reinforcement Mat (HPTRM) to promote vegetation and increase the factor of safety against slope instability. The system mitigates failure to the water and landside slopes of levees. Without adequate protection, overtopping or high velocities can lead to significant erosion and potentially a breach of the levee.
ARMORMAX has been tested by Colorado State University and the U.S. Army Corps of Engineers (USACE) on a full-scale wave overtopping simulator. Testing confirms that ARMORMAX provides increased levee resilience and durability and reduces the risk of a breach caused by wave overtopping.
Beginning in June of 2021, approximately 1,500 square yards of ARMROMAX was installed daily. Upon completion, 250,000 square yards of ARMORMAX will be installed on the levee. The installed ARMORMAX has quickly vegetated, providing erosion protection for up to 75 years.
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