Caltrans District 12 On-Call Environmental Analysis Services (Contract No. 12A1655)
Proposed improvements to SR-133 in Laguna Canyon may have adverse effects on the canyon floodplain. Performing floodplain and hydraulic studies has provided insight on the nature and extent of these effects, maintaining the integrity of the surrounding environment.
Caltrans is proposing several improvements that will address deficiencies on SR-133 in Laguna Canyon. These improvements will widen SR-133 to improve safety and efficiency, widen existing shoulders to provide a Class II bicycle lane, and construct a concrete check dam. Because the project occurs in proximity of the Laguna Canyon floodplain, evaluating potential floodplain encroachment is necessary to advance the project. Studies have been conducted to evaluate any negative effects the project may have, including determining if the improvements might raise the water surface elevation of the 100-year flood.
Floodplains offer many beneficial values that can be negatively affected by roadway encroachments.
To determine potential impacts to the floodplain, Advanced Civil Technologies prepared a Location Hydraulics Study and Floodplain Evaluation Report. Our team conducted research using available data from FEMA, Orange County Flood Control District, City of Laguna Beach, and US Army Corps of Engineers to identify longitudinal encroachments into the existing mapped floodplain. Additionally, Advanced Civil Technologies developed a custom hydraulics model by combining topographic data from Caltrans and USGS.
Once the Location Hydraulics Study, Flood Risk Assessment, and hydraulics modeling of the proposed improvements were complete, the findings were used to prepare the Floodplain Evaluation Report. This report discussed the impacts of the project on natural and beneficial floodplain values, risk assessment, alternatives to encroachment, and measures to minimize floodplain impacts. The data gathered played a critical role in allowing Caltrans to understand the potential impacts of their improvements, ensuring that the integrity and benefits of the floodplain will be maintained.
Close coordination with Caltrans District 12
Custom hydraulics model developed with combined data sets from Caltrans and USGS
Close coordination with Caltrans District 12
Custom hydraulics model developed with combined data sets from Caltrans and USGS
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Location Hydraulics Study
