Jefferson County Council Work Session Highlights GIS Growth and Possible Stormwater Policy Changes

Council members heard updates on the county’s mapping system before turning to drainage, flooding, and whether local stormwater rules may need to be modernized.

By The Jefferson Review

HILLSBORO — The Jefferson County Council used its June 1 work session to take a closer look at two issues that touch residents across the county: the county’s growing GIS mapping system and ongoing concerns about stormwater, drainage patterns, erosion, and flooding.

The meeting opened with an update from County Assessor Bob Boyer and GIS Coordinator Sandy Koss, who outlined years of work behind Jefferson County’s Geographic Information System, commonly known as GIS. Later in the meeting, council members turned their attention to stormwater, where comments from Council Chair Tim Brown and Vice Chair Charles Groeteke appeared to point toward the possibility of future changes to the county’s stormwater policies.

No final action was taken at the work session, but the discussion showed that stormwater remains a growing concern for the county, especially as heavier rainfall events, older subdivisions, drainage patterns, and development pressures continue to collide.

County GIS System Continues to Grow

Boyer introduced Koss, noting her long service with the county and her professional GIS designation. Koss has worked in the Jefferson County Assessor’s Office for 32 years and has helped guide the county’s mapping system through several major phases.

Koss explained that Jefferson County originally built its GIS system in-house, digitizing 871 mylar maps rather than outsourcing the project. She said that approach allowed the county to control costs. Around 2010, a $65,000 grant helped the county create an enterprise GIS system, allowing departments such as Planning and Zoning, Public Works, and the Assessor’s Office to work from shared geographic data instead of separate databases.

According to the presentation, the county’s total in-house investment at that stage was about $133,000, compared to an estimated $500,000 if the county had outsourced the work.

Koss also reviewed more recent upgrades. Beginning in 2019, the county started a quality control project to improve the accuracy of parcel lines across more than 100,000 parcels. The first phase covered roughly 70,000 parcels, while the second phase covered the remaining 36,000. The project also included rights-of-way, original lots, blocks, and other base map elements used throughout the GIS system.

In 2024, the county upgraded outdated GIS servers and software for about $12,000 and migrated GIS web applications, including the public property viewer, for an additional $8,500.

Koss said the GIS system now serves as a core enterprise tool for the county. More than 200 county employees use it daily, and the public-facing property viewer receives more than 1,000 users per day. The system is also integrated with other county programs, including permit-related software.

The county also continues to use EagleView aerial imagery, with flights conducted every two years since 2008. Koss said each flight costs about $125,000, with outside agencies contributing around $50,000 toward that cost.

The public GIS tools include the property viewer, FEMA flood information, school district lookups, trustee property sale maps, map galleries, and other applications. Koss said the county also maintains internal GIS viewers for departments such as Public Works, Elections, and the Assessor’s Office.

Council Members Ask About Usability

Council members also discussed how residents and elected officials use the property viewer.

Councilman Bob Tullock raised concerns that finding council district information appeared to take more steps than it did in earlier versions of the system. He said he recently tried to look up whether a resident was in his district while attending an event, but found the newer process more difficult and time consuming.

Koss explained that the information is still available, but users now have to turn on certain layers, such as county council districts, under the voting districts and elections section. She said the interface changed in part because of updates to Esri’s GIS platform.

Koss also said the county could create a simplified application focused specifically on county council districts, with the relevant layers already turned on by default. That type of tool could make it easier for residents and council members to quickly look up a property and determine which district it falls in.

Boyer said the GIS system has become much more than a parcel map. He described GIS as a type of “file cabinet” for county information, with the potential to store property photos, sketches, public works inventory, bridges, signs, storm sewer information, and other data.

Boyer said the county is working with the administration and Esri on a roadmap that could eventually move GIS out of the Assessor’s Office and into its own department. He said that could better serve multiple departments and improve efficiency countywide.

Councilman Billy Crow thanked Boyer and Koss for the work, saying he uses the GIS maps multiple times a day and appreciates how simple and useful the system has become.

Stormwater Discussion Turns Toward Policy

After the GIS presentation, the council shifted to stormwater.

Groeteke introduced the topic by saying stormwater remains a major issue for many Jefferson County residents. He said the county’s current stormwater regulations were established around 2012 and suggested that the county may need to look at updates.

That comment, along with later discussion from Brown, signaled that the council’s chair and vice chair may be opening the door to potential changes in county stormwater policy. While no ordinance was introduced and no vote was taken, the work session clearly placed stormwater standards, drainage patterns, and water velocity on the council’s radar for future consideration.

Mike Cook, who was invited to speak on the issue, told council members that the county’s current stormwater code does not require a dedicated or cleared 100-year conveyance path. In other words, while current plans may show ditches, swales, and other conveyance systems, they do not necessarily show where water will go when a storm exceeds the system’s capacity.

Cook said that makes it difficult to predict overland flow during major storm events.

He gave the example of a new development in Imperial that generated 12 phone calls related to drainage concerns. Cook said the issue is not always what happens directly next door, but what happens when water picks up volume and moves through several yards or properties.

Brown asked what standard the county currently uses. Cook said the county’s systems are generally designed around a 15-year, 20-minute storm event for certain conveyance systems. When rainfall exceeds that level, he said, it becomes harder to say with accuracy where the water will go.

Cook also said it is not realistic to engineer for every possible storm. Instead, he suggested the county should look at ways to improve its standards by reviewing manuals and regulations from other regions and adopting what makes sense for Jefferson County.

Velocity, Erosion and Older Rainfall Data

A major part of the discussion focused on water velocity.

Cook said Jefferson County currently does not have a velocity requirement that clearly states what different conveyance systems can handle. For example, a grass swale, block-lined swale, concrete swale, or riprap-lined channel may each handle moving water differently.

Without clear velocity standards, Cook said, fast-moving water can damage swales, create erosion, burden homeowners associations, and affect downstream rivers, streams, and creeks.

Cook also pointed to the county’s existing rain tables, saying they are roughly 20 to 25 years old. He suggested the county consider moving toward updated Atlas 14 rainfall data to modernize its code and better reflect current rainfall patterns.

Groeteke asked who the county should look to for model regulations or guidance on velocity standards. Cook said there are other counties and jurisdictions that could be reviewed, and that the Public Works director could help evaluate which examples may fit Jefferson County.

That appeared to be one of the clearest next steps from the discussion: county staff will look at stormwater regulations from other jurisdictions and determine what may be useful for Jefferson County.

New Development Versus Older Subdivisions

The discussion also touched on whether new development is causing the county’s stormwater problems.

County staff indicated that newer developments with modern detention basins are generally performing better than older subdivisions that were built before stormwater controls were common. Many older neighborhoods have little or no stormwater infrastructure, which can lead to water moving from yard to yard during heavy rain.

At the same time, staff acknowledged that new impervious surfaces — such as roofs, streets, driveways, and parking lots — increase runoff volume during flash flood or sustained flood conditions.

The point made during the discussion was not that new development has no impact. Rather, newer developments with detention basins are usually metering water out more effectively than older developments, as long as storms remain within the design standards. In larger flash flood events, however, more rooftops and pavement still mean more runoff.

Brown noted that some ideas, such as bioretention, may reduce volume but come with major drawbacks. He said bioretention areas can be difficult and expensive to maintain, can become a burden for homeowners associations, and may not work well in areas where soil does not infiltrate water effectively.

Staff also said bioretention typically treats only the first inch or inch and a half of rainfall, meaning it would not solve the kind of large-scale flooding residents are seeing during major storm events.

Groeteke noted that the county had a bioretention area on campus in the past, but it did not remain active. Staff said those systems require constant maintenance and can fail quickly if they are not properly maintained.

Heavier Rainfall Adds Pressure

Council members also discussed how rainfall patterns have changed in the region.

Tullock raised concerns about flooding in House Springs, where residents who have lived in the area for decades say they do not remember water rising the way it does now. He referenced a constituent who showed video of a dry creek rising to 10 or 12 feet in less than 12 hours.

Staff said higher rainfall totals appear to be a major factor. According to the discussion, the St. Louis region averaged about 34 inches of rain annually 15 to 20 years ago, compared to about 42 inches now. Staff also said the region has received more than 50 inches of rain in three of the last five years.

Those conditions leave ground and creek beds saturated more often, which means even one or two inches of rain can cause creeks to rise quickly.

The council also discussed FEMA floodplain map changes, which have caused some residents to receive letters saying their property is now located in a floodplain. Staff said the county’s floodplain administrator cannot simply change those designations because they come from FEMA. Residents must go through FEMA’s process if they believe their property should be removed from the floodplain.

Another issue discussed was creek maintenance. Staff said it was once common for rock and gravel to be removed from creeks and used on county roads. Today, that practice is heavily restricted, and permits through the Army Corps of Engineers can be difficult and costly to obtain.

No Vote, But Policy Conversation Likely to Continue

The council did not vote on any stormwater changes during the work session. However, the tone of the discussion suggested that stormwater policy may return in some form.

Groeteke said the county may need upgrades to its stormwater legislation. Brown asked detailed questions about the current standards and later described Cook’s suggestions as potential next steps, while also cautioning that no single policy can eliminate flooding or runoff during extreme events.

The likely areas for future discussion include updated rainfall tables, clearer 100-year overflow mapping, velocity standards for conveyance systems, and model regulations from other counties.

The meeting ended with a brief discussion about future work sessions. It was suggested that the council may pause regular work sessions for the rest of the summer unless an urgent issue arises. Brown said if something comes up that needs discussion, council members can send it over and a work session can be scheduled.

For now, the stormwater conversation remains unresolved. But the June 1 work session made clear that flooding, erosion, drainage patterns, and the county’s existing stormwater rules are still very much on the council’s mind.