Project Location
The Upper Santa Cruz River RiskMAP project follows the Santa Cruz River. It starts just upstream (south) of the Santa Cruz County Line and ends at Interstate 19. See the map below.
Project Description
The Upper Santa Cruz River RiskMAP project is a cooperative effort with the Federal Emergency Management Agency (FEMA) and utilizes the latest HEC-RAS computer riverine model developed by the Hydrologic Engineering Center of the U. S Army Corps of Engineers. The program is a 2-dimensional model that more accurately computes flow depths, velocities and areas of inundation. The current FEMA Flood Insurance Rate Map (FIRM) data for the Santa Cruz River is based on computer punch card technology and does not accurately reflect flood flow distribution. The RiskMAP products are not replacing the FIRM data or the current effective floodway delineations.
On July 17, 2018, there was a change the Scope of Work for the project to extend the modeling downstream to Interstate 19. The scope change also included revising the hydraulic model by upgrading to the newer version of the U. S Army Corps of Engineers HEC-RAS hydraulic program (version 5.05). The revisions produced slightly different results than the products previously shown on this website. Please contact the District if you need to view or obtain a copy of the initial product (12.3 Giga Bytes).
The Santa Cruz River was analyzed for the following discharge-flow return frequencies.
|
10-year
|
10%
|
15,570
|
|
25-year
|
4%
|
24,750
|
|
50-year
|
2%
|
33,750
|
|
100-year
|
1%
|
45,000
|
|
500-year
|
0.2%
|
100,500
|
Project Schedule
| LiDAR and Aerial Photography |
August 15, 2015 |
Explanation of LiDAR |
| RiskMAP report |
Completed
|
|
| Stakeholders Meeting |
January 25, 2018 |
Town of Sahuarita Mayor and Council Office |
| Sahuarita Town Council presentation |
February 26, 2018 |
Town of Sahuarita Mayor and Council Office |
| Public Open House |
March 13, 2018 |
Town of Sahuarita Mayor and Council Office |
|
Change order to extend the mapping north to Interstate-19
|
December 19, 2018
|
Upgraded the riverine computer model to HEC-RAS Vs 5.05 and extended the model downstream to Interstate-19
|
|
Project Completion
|
March 26, 2019
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The project was approved to be used as “Best Available Data”. This means District staff will compare the RiskMap data to the Flood Insurance Rate Map information and make regulatory decisions based on the greatest flood risk.
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The federal grant expired April 21, 2018.
Products
This project will create a report and flood hazard maps for five different flood frequencies. A copy of the Technical Data Notebook report (100 MB) on the Upper Santa Cruz RiskMAP Project is available for review.
There are five sets of 22 maps showing the flood risks along the upper Santa Cruz River for the 10-, 25-, 50-, 100-, and 500-year events. Go to the Maps tab to view the maps.
Flood Depth Maps
Click on the map number below to view the Flood Depth maps.
100-Year Flood Comparison Maps
Floodplain administrators are required to use is the 1% chance flood for permit regulations, according to local floodplain ordinances and state statutes. The 1% chance flood is often referred to as the 100-year flood. Although this RiskMAP project does not involve revising the Flood Insurance Rate Maps (FIRMs) approved by FEMA, they are an additional tool that floodplain administrators can use to assess flood risks and hazards. The most common question will be “What is the difference between the floodplains shown on the FIRMs and areas of inundation shown on the Flood RiskMAPs?" By clicking on the map below, users will be able to see the FIRM AE and AO flood zones and Floodway for the Santa Cruz River on top of the 100-year Flood RiskMAPs. Please note this comparison does not extend into Santa Cruz County and that the FIRMs do not show the 100-year limits inside Tohono O’Odham tribal lands.
Click on the map number below to view the Floodplain Comparison maps.
Videos
The District generated a map video showing depths and flow paths for the 100-year (1% annual probability) data. The MP4 video is a little under 3 minutes long and shows color coded flow depths and moving velocity vectors. Due to their size, you may be required to download the video and play it locally from your device.
Documents
Reports, Frequently Asked Questions and other documents will be placed here as they become available. Below are the currently available documents.