Floodplain Management


Floodplain Management Program Notes
Bill DeGroot, P.E., Chief, Floodplain Management Program

Planning for the future

One of the first and best policy decisions of the District was to delineate and regulate 100-year floodplains based on projected future development of the watershed. I was reminded of this fact again recently when the 2000 census numbers were released and we found that Colorado had added a million people over the last ten years, with most of them landing in the District’s area.

Even though this makes all the sense in the world we still have lots of developers and their engineers insisting that they should only have to address the historic discharges. We constantly have to educate these folks that urbanization dramatically changes the watershed hydrologic regime, and those changes have to be accounted for in order to provide for the health, safety and welfare of our citizens and their customers. The surest way of doing that is to use future conditions hydrology.

Our preferred approach continues to be to stay out of the floodplain, thereby preserving its natural and beneficial values while minimizing the risk to new development. David Mallory’s cover story details examples of several successful developments where the developer has set aside open space along major drainageways, to the benefit of all concerned.

Another approach, which we have been putting into many of our recent master plans for developing areas, is regional detention. The advantages of regional detention are that you can own it, maintain it, and know that it will be there when needed. The major disadvantage is getting the funding to get it built by the time it is needed. More on this topic below.

The year in review

We continue to be just about maxed out on development referrals, and it is a constant struggle to assure that new development doesn’t increase the flood hazard potential within the District.

Our maintenance eligibility program continues to expand under David Mallory’s direction. He currently has over 200 separate projects somewhere in the process between design review and final acceptance of construction. Unfortunately, most projects, no matter how simple, require two, three or even four submittals.

Kevin Stewart continues to assure that we have the best possible flood detection system, and he continues to be in demand as an expert in this field (see his list of professional activities on page 20 and his column in this issue). If you check out our web site at www.udfcd.org you will also see Kevin’s handiwork.

Implementation efforts

One real challenge has been to implement portions of our master plans, particularly regional detention facilities, as development occurs. We have had some successes over the last couple of years that I would like to highlight.

The E-470 Public Highway Authority has helped build the first phase of detention ponds where their highway construction crossed East Toll Gate Creek and Tributary T to First Creek. They also constructed their crossing of Second Creek such that it is compatible with the plans for future implementation of a detention pond at that location. Finally, their plans for their final construction phase include borrow areas on Third Creek and Buffalo Run Tributary which will be converted to detention ponds. We’ve had some battles along the way but we do appreciate and acknowledge the Authority’s efforts.

We have negotiated an intergovernmental agreement (IGA) with Aurora, Denver, Gateway Regional Metro District and Town Center Metro District (Oakwood Homes) for implementation of the regional detention facilities called for in the upper First Creek master plan, including cost sharing for two of the facilities, Green Valley Ranch Golf Course Pond and Blue Grama Pond. The IGA calls for Town Center to construct the Green Valley Ranch pond in conjunction with golf course construction and to be reimbursed by the other parties. Even though the IGA is still in the signing process, Town Center went ahead and built the Green Valley Ranch pond. I appreciate their willingness to do that.

Perhaps the most gratifying project, however, was the construction of what we call Parkfield II Pond by American Realty Trust (ART) on the Rocky Mountain Arsenal (RMA). We have been trying for six years to negotiate intergovernmental agreements between Denver, the RMA, Commerce City, Adams County and the District for the implementation of the Irondale Gulch master plan.

Finally, everything came together in 2000 for this one facility. The US Fish and Wildlife Service (USFWS), ART and Denver signed the agreement and construction began. The key elements of the agreement are that the USFWS, acting on behalf of the RMA, allowed the facility to be built on the RMA; the project creates 6.9 acres of new wetlands, ART funded the project and built it; and Denver agreed to accept maintenance responsibility for the facility. Our involvement was to approve the facility for District maintenance eligibility. We expect Denver to request our maintenance assistance out of the Denver allocation of District maintenance funds.

With that success under our belts, we have begun preparation of an environmental assessment (EA) of the remaining master planned facilities proposed on the RMA. Our hope is to have an EA approved later this year, which will then allow us to implement these facilities over time as needed. ERO Resources/Sellards and Grigg is the consultant.

Finally, we completed an interim implementation plan for Third Creek. We know that implementation of the master plan will be a long time coming. In the meantime development of the upper watershed is underway, and the lower Third Creek facilities are very limited in their capacity. This plan will help us buy some time before the full master plan facilities will be required. HDR Engineering prepared the plan.

FEMA news

I continued to represent the National Association of Flood and Stormwater Management Agencies (NAFSMA) as an advisor to FEMA’s Technical Mapping Advisory Council. The council’s authorization expired in November. Its final report is being printed, and, along with FEMA’s proposed map modernization plan, offers great hope for future maps. However, until FEMA receives some significant funding source ($750 million over seven years), most of these recommendations will languish.

Our Cooperating Technical Communities (CTC) activities were fairly limited this year. In March we felt we had reached an agreement with FEMA to assume the review of requests for Letters of Map Change (LOMCs). In fact we even selected a consultant to assist us with that effort. However, at the last moment FEMA’s lawyers found something they didn’t like, and we have been unable to finish the deal.

We received a small grant from FEMA from funds allocated to CTCs. We used the funds to combine AutoCAD files from our Willow Creek Flood Hazard Area Delineation (FHAD) study and Douglas County GIS roadmap files using FEMA’s Digital Flood Insurance Rate Map (DFIRM) specifications. We used that experience to develop guidelines for our consultants to use on future FHADs to assure maximum compatibility with future DFIRMs. Our consultant was Merrick and Company.

A pet peeve

One of my pet peeves is developer engineers who look at a FIRM and if no floodplain is shown, declare their project to be free of flood hazards. Never mind the size of the channel on their site or the size of the tributary watershed. Never mind the fact that the Flood Insurance Study that created the FIRM is 20 years old and that the drainageway wasn’t studied then because it was way out in the boonies. And never mind that the District delineated the floodplain several years before. If it’s not on the FIRM, there is no hazard.

Lakewood City Engineer Jay Hutchinson has asked FEMA to put the following note on Lakewood’s FIRM and they have agreed to do so: "Local community floodplain management requirements may apply in areas other than specific zones shown on this Flood Insurance Rate Map. Contact the local community for specific requirements." Maybe it will help.

Master planning efforts

Somehow I ended up managing two difficult master planning projects, even though the District has a separate Master Planning Program. I’m certainly going to be more careful in the future so that that doesn’t happen again.

We have completed the Phase A portion of the master plan revision process for the lower portion of the First Creek watershed. We expect Commerce City and Adams County to select an alternative for preliminary design by the end of February, and the new master plan to be done by the fall. We have also been re-delineating the First Creek floodplain and delineating some tributary floodplains for the first time. Our consultant is Turner, Collie & Braden.

We have also completed the Phase A for the South Boulder Creek master planning effort. This is the District’s third attempt to prepare a plan that has a chance to be implemented. We should know by April if we have been able to devise an alternative acceptable to Boulder, Boulder County and the University of Colorado.  Our consultant is Taggart Engineering Associates.

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