Duncan Floodplain Analysis-Project Understanding |
 |
Duncan Floodplain Analysis-Project Understanding |
|
Home page Project Understanding Documents Photo Gallery
Project Location:
The project is located in Southeastern Arizona along the Gila River (Figure 1). The Gila River runs next to a town called Duncan, Arizona where the design team will conduct the flood mitigation study (Figure 2). This town has a current population of about 800 residents, according to the 2015 census. This town has experienced consequential flooding events throughout its history due to its geographic location on the floodplain. The floods that occurred in 2005 and 1978 caused significant damage to infrastructure, agricultural crops, and property [1]. Therefore, Ponderosa Designs has been contracted to protect the town from future flooding. The purpose for this study is to define and evaluate possible mitigation measures to alleviate flooding in the town of Duncan and the surrounding area.
Figure 1: Project Location: Duncan, Arizona [1]
Figure 2: Duncan, Arizona and Gila River
Project Constraints:
The project constraints for this project include learning how to use all of the modeling programs, having no prior experience with these modeling programs, and correspondence with the technical advisor. The technical advisor works in a different town so the only communication is through occasional meeting, phone calls, and emails. In addition, the technical advisor has the ability to process all the QGIS data for FLO-2D. This makes it problematic to troubleshoot modeling errors efficiently. In addition, the team must design for the 100 year storm (48,000 cfs), make no alterations to the shape of the channel, and keep the economic and environmental needs of the public in mind. All of these constraints will impact the team’s final design solution. The modeling software used for this project are QGIS and HEC-RAS. Results from both applications go into a software called FLO-2D that exports a Google Earth animation of the design alternatives that were inputted (Figure 3).
Figure 3: Modeling Application flow chart
List of Tasks:
Table 1: List of project tasks.
Design Alternative Options:
Table 2: Design alternatives generating within HEC-RAS.
Project Management:
Table 3: Total hours accumulated on the project.
Final Design:
The final design that was chosen for this project was a combination of the most effective HEC-RAS and QGIS models. As for HEC-RAS data, the “Highway Relocation without Fence” model was chosen and imported into FLO-2D. This alternative was chosen because it created the greatest water surface drop and simulated the most realistic scenario of hydraulics at the bridge (debris blockage and having a pier shape). In addition, the fence could potentially drop down during a flood stage so the team went with this option since it modeled the best case scenario. The water surface was around 5 feet so the team added a extra 3 feet of freeboard to get a total levee height of 8.5 feet. The QGIS model, “Levee/Highway Alignment” was imported into the same FLO-2D model to create the final design. This will be a combination of improving hydraulics at the Highway 75 bridge and creating a Levee/Highway alignment. This will be a levee that the Highway 70 will move over. All in all, this highway/levee alignment is 8.5 feet above existing ground surface, has a width of Approximately 101 feet (max), and a length of 2.75 miles (Figure 4). This was chosen because it meets project goals more effectively than the other scenarios. This includes protecting the town against 100 year flood, having potential ADOT funding ,and causing no significant changes to the channel shape. The characteristics of the levee/road are described in Figure 5-6
Figure 4: Proposed Solution Highway Alignment
Figure 5: Auto CAD Representation of Roadway Cross Section
Figure 6: Auto CAD Representation of ROW Offset from Railroad to Roadway
