Agenda Date: 10/20/2026
Subject:
Title
Resolution 77-2026: Approving the Intergovernmental Agreement with Urban Drainage and Flood Control District D/B/A Mile High Flood District regarding development of a district-wide flood risk assessment
Body
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From: |
James L. Becklenberg, City Manager |
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Prepared by: |
Brent Soderlin, Director of Public Works & Utilities |
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Sarah White, Water Resources Manager |
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Presentations: |
N/A |
PURPOSE:
Approval of an Intergovernmental Agreement (IGA) between the City of Littleton and Urban Drainage and Flood Control District D/B/A with Mile High Flood District (MHFD) to develop a district-wide flood risk assessment.
LONG-TERM OUTCOME(S) SERVED:
Safe Community; High-Quality Governance; Sustainable Community with Natural Beauty
DISCUSSION:
Floodplain management promotes public health, safety, and welfare by permitting the movement of water during storm events, minimizing flood loss and damage. Watershed planning is an important way to help protect people and property against flooding, erosion, and stormwater quality problems. These plans contain a strategy and work plan to identify flood risk management projects, guide new land development projects and identify high risk areas. The City of Littleton has adopted 13 major drainageway master plans and a flood management program to provide regulation for their implementation.
Floodplain regulations are currently established with a binary description “in or out” of the special flood hazard area (SFHA aka 1% annual chance flood or “100-year floodplain”). Properties within the SFHA are required to comply with certain floodplain regulations as established by FEMA and the Colorado Water Conservation Board and further adopted by the City of Littleton Municipal Code. However, flood risk is not that simple, making it difficult to communicate risk and prioritize flood mitigation projects. While prioritization can already be challenging within a single watershed, it becomes even more difficult across watersheds and city boundaries, where projects are compared without a consistent framework and prioritization is often based on anecdotal evidence.
MHFD in collaboration with the City of Littleton and other local jurisdictions are proposing the participation in the MHFD Flood Risk Program Foundational Data project. This project’s goal is to supplement the existing “in or out of the floodplain” regulations, by creating additional models to show the graduated flood risk using reliable, repeatable methods. The Program is not intended to modify regulatory floodplains or create new regulatory designations. Instead, it will build the foundational modeling tools and data that could support future mapping or revisions to local regulations. While there are many applications for high-resolution flood information, the program implementation focuses on the following aspects:
• Creating a shared, district wide flood data system. The data building process will be thoroughly reviewed by MHFD and all partner jurisdictions.
• Improving how flood mitigation projects are prioritized. The new data will help compare projects more fairly and improve transparency in spending decisions.
Phase 1 of the project (District-wide modeling + risk assessment) will occur over the next three years. Work begins in late 2026 and is expected to finish in 2029. Phase 1 is estimated to cost $4.9 million. MHFD will cover 50% of the project costs and is seeking a 50% match from each local government partner. Costs are prorated based on watershed characteristics, including size, development, hydraulic structures, stream length, storm drains, and calibration gauges.
The total matching funds request for Littleton is $30,900, a 1.2% cost share. The fund request will be split into 2 billing years, $10,000 in 2026 and $20,900 in 2027.
BACKGROUND:
City-wide flood models, such as the City and County of Denver’s Flo-2D modeling have been explored previously and have been implemented to great success. Denver has utilized this data to create their Urban Flood Risk Area map, which is intended to supplement existing floodplain maps by also showing expected flood depths along the areas that were studied, allowing residents, developers, and other users better understand the potential flood risk with certain areas of the city, beyond the “in or out of the floodplain” designation.
Older models often only consider major waterways and ignore local stormwater flooding resulting in significant gaps within the data. In addition, the framework used to create these older models may also vary from one watershed to another, making it impossible to combine existing models into one consistent city-wide picture. Stormwater doesn’t follow city boundaries, therefore coordination with other jurisdictions is critical to ensure the results of these models are both accurate and up to date with any recent developments that may impact the floodplain. This can make consistency in recordkeeping difficult when many jurisdictions are only concerned with keeping their own information up to date, rather than considering the greater watershed and looking at any upstream or downstream impacts.
MHFD plans to address these challenges by enacting a portfolio-management approach of the collected data, which considers the full District and/or local government jurisdictions, rather than individual watersheds, which includes local storm flooding. In addition, MHFD has developed a programmatic framework to ensure consistency across all flood models that will be used for data collection as a part of this effort. This framework marks a shift in watershed modeling methodologies from the historical models that are currently used by MHFD for regulatory purposes.
A smaller pilot project was completed in Goldsmith Gulch between 2024 and 2025. Per MHFD’s results from the pilot, the new modeling framework more closely matched observed flooding conditions while old methodologies consistently overestimated peak flows and produced earlier, sharper peaks. While the conservative assumptions associated with older methodologies can support regulatory compliance, they frequently lead to overdesign and inflated mitigation costs.
With promising results observed within the Goldsmith Gulch Pilot Study and lots of applications for high resolution flood data, MHFD is promoting this study district wide.
Major drainageway plans will continue to be produced to help the city follow FEMA and State floodplain regulations. Flood Insurance Rate Maps produced by FEMA denote areas associated with the mandatory purchase requirement and additional regulations. This flood risk assessment model will supplement mapped SFHA to include flood risk across the entirety of the City of Littleton. Hazard information (depth, velocity, and flood force) will be intersected with people-proxy receptor datasets (population, buildings, roads, trails, and critical facilities) to develop graduated risk information across the city. The city will be able to use these hazard and risk metrics to identify mitigation projects across the city not just within the SFHA.
Prior Actions or Discussions
N/A
FISCAL IMPACTS:
Approval of this IGA authorizes the City of Littleton to contribute 1.2% cost share of $30,900.00. The fund request will be split into 2 billing years, $10,000 in 2026 and $20,900 in 2027.
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Funding Source |
Funding Amount |
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City of Littleton Account 4200-313-74210 |
$30,900 |
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MHFD CIP Match Funding |
$2,481,017 |
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Other participation jurisdictions |
$2,450,100 |
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Total |
$4,962,017 |
STAFF RECOMMENDATION:
Staff recommends approval of the IGA.
ALTERNATIVES:
If not approved, the city would not be able to contribute to a district-wide flood risk model.
PROPOSED MOTION:
Proposed Motion
I move to approve Resolution 77-2026 approving the Intergovernmental Agreement with Urban Drainage and Flood Control District D/B/A Mile High Flood District regarding development of a district-wide flood risk assessment.