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Location: Surprise, Arizona
Client: City of Surprise

BNSF Railroad LOMR

Hoskin Ryan was directly contracted by the City of Surprise to prepare hydrologic and hydraulic models and prepare a LOMR to potentially modify the effective FEMA floodplain designation that impacted development opportunities near the BNSF Railroad from Sweetwater Ave. to Peoria Ave. Our work involved extensive research of the available hydrologic models and a re-evaluation of the watershed using HEC-1 models. This entailed modifying the watershed by including flow splits and retention basins upstream of the floodplain. These modifications substantiated a major reduction of the 100-year flow from more than 300-cfs to 91-cfs. A HEC-RAS hydraulic model based on new topography was created to re-delineate the floodplain limits. The hydraulic model results demonstrated significant reduction in the floodplain west of the BNSF Railroad and completely eliminated it east of the railroad. This recent experience gives us a distinct advantage of understanding the drainage issues related to Litchfield Road and Cactus Road. Hoskin Ryan worked closely with the Flood Control District of Maricopa County on all the modeling results and received their approval as well as FEMA’s on the LOMR.
Project Requirements / Unique Characteristics:

  • Peak Flow Reduction
  • Detailed Floodplain Modeling
  • Significant Floodplain Reduction
  • FEMA LOMR Approval