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Floodproofing Guidance

City of Englewood

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DRAFT

DRAFT

The approach to the floodproofing study included:

  • Reviewing and documenting other past studies in the area

  • Providing supplemental calculations to bring the standard of data into more modern hydraulic and hydrologic modeling software

  • Walking the subject area

  • Surveying and talking to area residents and business owners

  • Soliciting input from homeowners

  • Researching reference documents and standards of practice related to floodproofing of homes

 

To find information related to the OSP update and hydraulic and hydrologic modeling for the area, click on the menu item OSP Update above. 

 

To read more about previous studies and the history of flooding in the area, click on the menu item History of Flood Studies above. 

The information provided below includes articles, links, documents, data, and maps to demonstrate what we learned from area residents and about properties within this area.

Overall Methodology

The subject floodproofing study included:

  • Preliminary site walks of all study basins (see Basin Map) 

  • Utilizing previous hydraulic models (TCB, 1999) to determine homes most likely to experience flooding

  • Site walks and/or field visits of individual homes

  • Estimation of flood damage risk and life-safety risk based on site walks and/or field visits

  • A citizen survey requesting information on flood occurrences at individuals homes, sent to over 4000 homes and email addresses within and around the study area (including, but not exclusive to, address, last occurrence of flooding, depth of flooding, damages incurred, historic flooding, etc.)

  • Letters sent to critical life risk homes advising immediate floodproofing of homes and describing applicable and optional techniques 

  • Phone calls and emails to critical life risk homes to set-up in-person meetings with Calibre and representatives of the City of Englewood

  • Research, review, and analysis of various floodproofing techniques, including FEMA, USACE, the City and County of Denver, the City of Aurora, and UDFCD

  • Development of schematic-level floodproofing options for individual and local floodproofing

  • Citizen meetings to present and share findings and floodproofing options

 

It should be noted that initial estimations during our preliminary investigations were used as a guide to help focus the study and were not intended as comprehensive evaluations of individual property risk. 

 

The scope of the subject study did not include detailed on-site inspections of the interior of each lot or the interior of each home. Therefore, conclusions were limited to what was visible from the streets and alleys.

 

Field Work & Field Data

The subject floodproofing study began with preliminary site walks of all study basins (see Basin Map above). Using previous hydraulic models from the 1999 TCB study as a guide to determine which homes might have experienced the most flooding, each house was visited (walk-by site visit) and an initial estimation of flood damage risk and life-safety risk elements were noted if visible from the street or alley.

 

It should be noted that this initial estimation was used as a guide to help focus the study, and was not intended as a comprehensive evaluation of individual property risk. The scope of the study did not include detailed on-site inspections of the interior of each lot or the interior of each home, so conclusions were limited to what was visible from the streets and alleys.

As a result of site walks:

  • A home was considered "Low Life Risk" if a basement was not present and the home was expected to experience low or no floodwaters. 

  • A home was considered "Moderate Life Risk" if either a basement was present with low risk of flooding or a basement was not present but moderate floodwaters were expected against the walls of the occupied areas.

  • A home was considered "High Life Risk" if a basement was present with no visible forms of egress (escape) or small, non-egress windows were present and high floodwaters were expected. 

  • A home was considered "Critical Life Risk" if a basement was present with an outdoor stairwell at or close to ground level as the only means of egress or if floodwaters exceeded 3 feet.

 

 

 

Utilizing the field data and data taken from citizen surveys (see Public Contact), homes were classified in a risk category, and each of the critical life risk homes were contacted individually with a letter recommending immediate flood-proofing of the home, describing techniques that might be applicable to their residence, and asking them to contact the City for assistance.

 

In addition, individual 'Critical Life Risk' properties were contacted to set up an in-person meeting, during which the project team further delineated the property flood risk. Further notes on these home visits can be found under Public Contact and on the Survey Results page.

This flowchart was developed as a quick at-a-glance tool to determine whether homeowners should implement floodproofing on their properties. This flowchart is meant to be a guidance document, and homeowners are encouraged to use their discretion and past experience to determine risk of flooding.

Click this button to navigate to a page dedicated to floodproofing techniques.

What does it mean to experience an

"X-Year Storm Event"?

An Analogy:

Think of a 5-year storm event as a cup with four white marbles and one red marble. If you randomly pick one marble out of five, the odds of you picking out the red marble is one out of five. If you replace the red marble and pick again, the odds of picking the red marble are still one out of five. But, you could in fact pick the red marble twice in a row. This is the same with the 5-year storm event. The odds of experiencing the 5-year storm are one out of five in a given year, but it could happen twice in a row, even in the same week.

The same is true for a 25-year, 50-year, or 100-year storm event. A 100-year storm event is like having 99 white marbles and one red marble. The odds of picking a red marble are one out of 100, but you could draw that red marble at any time, even twice in a row.

Understanding a

"STorm Event"

In order to quantify and identify flood problems within the study area, Calibre conducted a survey of local residents. The survey yielded a number of areas of concern, and Calibre provided additional one-on-one and public meetings to learn more about the flooding and to educate the public on residential flood proofing.

For more information, please visit the Survey Results page.

This interactive map shows key locations of flooding as determined by modeling, citizen input, and City records. It also includes images, comments about flooding, basin boundaries, and other relevant information.

These maps demonstrate the Areas of Probable Flooding and flood water depths in the basins included in this study. If you are a citizen or business owner in Englewood, these maps can help you determine your risk of flood at your home or property. The "Areas of Probable Flooding" Maps will show you where the Areas of Probable Flooding are within each basin. The "X-Year Depths" maps will show approximately how much inundation might be experienced at a property in a given storm. 

Note: A 100-year storm event does not necessarily occur exactly once every 100-years. Every year there is a chance that a 100-year storm could occur, regardless of the timing of the previous occurrence. Similarly, there is a chance that a 25, 10, or 5-year event could occur in any given year. For more information see "Understanding a Storm Event" above.

Public Contact

Citizen input was critical to the Calibre Team and the City of Englewood in establishing and identifying high risk flood areas. For this project, the public process included:

  • Citizen survey

  • 4000 emails, letters, and post cards to solicit feedback on residential flooding

  • One-on-one meetings with Critical Risk properties

  • Sitewalks of Critical Risk properties

  • Public meeting

  • Attendance at City Council meetings

 

Over 4000 email and letter surveys were sent to citizens within and around the study area. These surveys asked questions as to the extent of flooding occurrences at a residence, for example, address, last occurrence of flooding, depth (approximate) of flooding, damages incurred, and historic flooding issues. Just over 50 people responded to the mailed survey.

Once all of the houses in the study area were classified in a risk category, each of the critical life risk homes were contacted individually with a letter recommending immediate flood-proofing of the home, describing techniques that might be applicable to their residence, and asking them to contact the City for assistance.

Once these letters were sent out, individual homeowners/tenants that were considered to be in the 'Critical Life Risk' category were contacted via phone, letter, or email in order to set up an in-person meeting with members of the Calibre team and representatives from the City of Englewood. During these home visits, it was noted in further detail the risk that the property may be facing qualities of the property that protect against or increase flood risk, and possible solutions for the homeowner to consider. Further notes on these home visits can be found on the Survey Results page of this site. 

Calibre hosted a City-sponsored open house presentation to meet with the citizens of Englewood regarding local floodproofing. This open house included:

  • The opportunity to provide comments on maps of Englewood neighborhood maps

  • The opportunity to see the Calibre flood models and 2D updates to the existing model

  • A preliminary discussion of potential stormwater projects to reduce or eliminate flooding

  • Information and advice on various local and residential floodproofing techniques with images and schematic-level designs

 

In addition to the letters that were sent to critical risk homes, this study and the resulting website are available to all concerned citizens that would like to reduce flood impact to their homes.

Reported Flooding & Related Problems.PNG
north basins areas of probable.PNG

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This interactive map shows the Areas of Probable Flooding by storm event in the North Englewood and Yale Basins with the current City of Englewood infrastructure.

south basin areas of probable.PNG

This interactive map shows the Areas of Probable Flooding by storm event in the South Basin with the current City of Englewood infrastructure.

central basins areas of probable.PNG

This interactive map shows the Areas of Probable Flooding by storm event in the Central Basin with the current City of Englewood infrastructure.

5 year flood depths at buildings.PNG
10 year flood depths at buildings.PNG

This interactive map shows the approximate depth of flood waters at buildings within the study area in the 5-year storm event. If you are a citizen or business owner of a building impacted by the 5-year storm, your risk of flood inundation is very high, and your property is sure to be impacted by flooding. You should obtain flood insurance.

This interactive map shows the approximate depth of flood waters at buildings within the study area in the 10-year storm event. If you are a citizen or business owner of a building impacted by the 10-year storm, your risk of flood inundation is high, and your property is very likely to be impacted by flooding. You should obtain flood insurance.

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25 year flood depth at buildings.PNG
100 year flood depth at buildings.PNG

This interactive map shows the approximate depth of flood waters at buildings within the study area in the 25-year storm event. If you are a citizen or business owner of a building impacted by the 25-year storm, your risk of flood inundation is moderate, and your property is moderately likely to be impacted by flooding. You should obtain flood insurance.

This interactive map shows the approximate depth of flood waters at buildings within the study area in the 100-year storm event. If you are a citizen or business owner of a building impacted by the 100-year storm, your risk of flood inundation is lower, and your property is less likely to be impacted by flooding. However, your property is still at risk, and you should obtain flood insurance.

Published June 11th, 2019