Tuesday, May 28, 2013

Check your risk on the new flood map

Posted By on Tue, May 28, 2013 at 4:33 PM

Flood_cover_image.png

For the average home or business owner, the Preliminary Flash Flood Risk Analysis for the Waldo Canyon Burn Scar — also known as the inundation study — is by far the most interesting piece of information to be released about our flood risk since the fire.

This isn't a study full of complex ideas — it's a map. Based on early assumptions about the burn, the map shows how water and debris would spread in a 10-year flash flood. Areas shaded green would be under less than two feet of water. Those in yellow would see two to four feet. The red areas would have more than four feet of water.

Flash flooding happens very quickly, making it extremely dangerous. Experts are urging residents to locate their homes and businesses on the map and make emergency plans if their structures are threatened.

If you live in Colorado Springs, the best place to look at the map is here. There's a large searchable map, but it can be difficult to use. It's likely easier to click on the link that corresponds with your area.

If you live in the county, check here for your map.

The inundation study is continuing and will produce much more detailed and accurate information in the coming months. These maps are considered preliminary, and are intended to give citizens a better idea of their personal risk. The city will be holding meetings with residents to discuss the maps and emergency planning.

The following information is from the city:

In an effort to ensure Colorado Springs residents are aware of potential flash flooding scenarios, we are sharing the initial findings of the Preliminary Flash Flood Risk Analysis for the Waldo Canyon Burn Scar. These findings are only preliminary and the final report is anticipated to be complete and released to the public by the end of July.

Purpose
• El Paso County, the City of Colorado Springs, the State of Colorado Water Conservation Board, and El Paso County Regional Building funded a flash flood study to determine the potential impacts that a 10-year rain storm (1.75” of rain in one hour) over the Waldo Canyon Burn Scar would have along Fountain Creek (Sand Gulch to 31st street), Camp Creek, North Douglas Creek and South Douglas Creek.
• The study was conducted by Matrix Design Group, located in Colorado Springs.
• The first phase of the Flash Flood Risk Analysis for the Waldo Canyon Burn Scar involved initial mapping of the potential flash flood risk areas for the select watersheds mentioned above.
• This information is being provided to the public so they can make appropriate preparations for a flood event. A goal of this study is to prepare initial flash flood mapping to inform local residents of at-risk areas as quickly as possible before the normal mid-summer rainy season begins. The burnt soil could rapidly shed rainfall and is expected to result in larger and more frequent flash flooding. Due to the desire to expedite the release of this information, project stakeholders elected to use readily available, published hydrology values to create this initial map.
• The second phase of the study will involve more detailed evaluation of post-fire flood hydrology and hydraulics for some of the study boundaries. Hydrologic modeling will be developed for ½”, ¾”, 1”, 1½” and 2” rainfall events that may occur within a one hour period. This phase will be released by the end of July.

How Residents Can Access the Flood Study Map
Mapping for the Preliminary Flash Flood Risk Analysis for the Waldo Canyon Burn Scar is available for the public at www.Springsgov.com/floodinfo. Residents can enter their street address and view where their property is in relation to the at-risk areas for flash flooding. Residents should read the disclaimer on the map to help them understand the parameters of the study and how they should interpret the information.

How residents can determine their flood risk using the interactive maps
Two maps have been made available on the www.springsgov.com /floodinfo website.
•The “Waldo Canyon Fire: Post Fire Flood Risk Map Viewer (FEMA)” provides an illustration of the FEMA 100-year flood plain boundaries. These boundaries are used to determine recommendations for flood insurance though the Federal Government.
• The “Preliminary Flash Flood Risk Analysis for the Waldo Canyon Burn Scar” gives the results of the initial study flash flooding inundation areas along the creek drainages below the burn scar. This new data provides estimates of places where water may overflow the channels, sometimes moving into residential and business locations. This data contains additional information regarding the use of the maps in a disclaimer.

Flash Flood Map Disclaimer
Based on initial study results this map shows approximate areas of potential flash flooding expected from a single rain event of 1.75 inches in a one hour period occurring over the drainage basins affected by the Waldo Canyon Fire. A rain event this severe has about a 10 percent chance of occurring each year. These areas were determined assuming debris in flood waters cause blockage at street crossings. Limits and depths are approximate as a wide variety of storms can produce much greater or much less of a flood risk zone. This information is not intended for flood insurance purposes or to replace established FEMA floodplains. Individual property owners are solely responsible for determining their risk level and taking appropriate actions to ensure their own safety and protect property. This is the best information available as of May 15, 2013 and is subject to revision upon release of final study results.

Assumptions
The new Flash Flood Risk map shows areas with a potential for flash flooding along the creeks and spillways. Depths less than 2 feet deep are displayed as green, 2 — 4 feet deep in yellow, and greater than 4 feet deep is red. While this is preliminary information, our intent is to provide residents and businesses with the best information we currently have in order to be prepared as we approach the summer rainy season.

The hydrology used was developed by the Department of the Interior National Interagency Burned Area Emergency Response team (BAER). Before the fire was fully contained a BAER team was evaluating the burned area for threats to life and property due to post-fire flooding and erosion.

City to Engage Residents Directly
The City of Colorado Springs Office of Emergency Management will host two preparedness meetings for businesses and residents along the waterways for North and South Douglas creeks as they have newly-identified areas at-risk for flash flooding.

The meetings will specifically address potential impacts on North and South Douglas creeks. Residents in the newly identified at-risk neighborhoods will receive a postcard invitation by mail to attend one of the preparedness meetings. The public is encouraged to review the maps at www.springsgov.com/floodinfo to determine their flood risk. The preparedness meetings are open to the public.

Residents - North and South Douglas Creeks
Tuesday, June 4
6-8:30 p.m.
Front Range Alliance Church
5210 Centennial Blvd

Businesses - North and South Douglas Creeks
Thursday, June 6
1-3 p.m.
El Paso County Citizens Service Center, Room 1020
1675 West Garden of the Gods Rd

WARSSS Study v. Preliminary Flash Flood Risk Analysis for the Waldo Canyon Burn Scar. The Preliminary Flash Flood Risk Analysis for the Waldo Canyon Burn Scar, as well as the Waldo Canyon Fire Watershed Assessment of River Stability and Sediment Supply (WARSSS) study from Wildland Hydrology were commissioned to determine the areas of greatest concern for flooding from the Waldo Canyon Burn Area.
• The WARSSS study predicts where sediment and debris will come from the Waldo Canyon burn scar and identifies methods to stop it.
• The Waldo Canyon Burn Scar Flash Flood Preliminary Risk Analysis, which will be completed by the end of July 2013, provides an initial assessment of where water will most likely flow as the waterways meet with populated areas.

Current flash flood mitigation efforts for Colorado Springs
The city is investing $8.8 million dollars in flash flood mitigation efforts related to the Waldo Canyon Fire to rebuild/restore the existing downstream concrete channels. In addition, $8.2 million in Emergency Watershed Protection Funds will be used in the burn area for construction projects that will lessen the amount of debris entering downstream drainage facilities. This includes debris catchment facilities (large holes), debris fences, aerial mulching and seeding.

Estimated Damage and Likelihood of New Flood Event Occurring
This model is based on a flood scenario that has a 10 percent chance of occurring annually. It included several factors that could vary based on the extent and areas of flash flooding. Therefore, it may cause little to no damage, or significant damage. In the interest of ensuring our community has the best information available, the City of Colorado Springs is sharing these initial findings for residents to make informed decisions about their property and safety.

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