Rooftop to River
The Tulsa Program
Tulsa's floodplain and stormwater program includes three key goals:
This section highlights major program elements used to achieve those goals.
In general, Tulsa growth is welcomed -- so long as it will not flood or cause flooding elsewhere.
Beyond the 100-year standard*
Experience showed that the National Flood Insurance Program's minimum standard is insufficient for Tulsa. Therefore, the city's regulations exceed NFIP's standard in several important ways, highlighted below.
Ultimate watershed urbanization.
Runoff generally becomes deeper and faster, and floods become more frequent, as watersheds develop. Water that once lingered in hollows, meandered around oxbows, and soaked into the ground now speeds downhill, shoots through pipes, and sheets off rooftops and paving.
Insurance purposes require the NFIP floodplain maps to be based on existing watershed development.
But unless plans and regulations are based on future watershed urbanization, development permitted today may well flood tomorrow as uphill urbanization increases runoff. Tulsa enforces the NFIP minimum regulations and maps, to retain eligibility for federal flood insurance.
In addition, the city enforces its own more extensive maps and regulations, which are based on ultimate watershed urbanization as forecast in the comprehensive plan.
Floodplains are only part of flood-management considerations. Water gathers and drains throughout entire watersheds, from uplands to lowlands. Each watershed is an interactive element of the whole. A change at one place can cause changes elsewhere, whether planned or inadvertent. Therefore, Tulsa goes above and beyond the floodplain in its regulatory program, extending its regulations watershed-wide.
Stormwater detention. One way to avoid increased flooding downstream from new development is to provide stormwater detention basins throughout watersheds.
New or substantially improved developments must detain the excess stormwater on site -- unless they are exempted in master plans or allowed to pay a fee in lieu of on-site detention. Water from detention basins is released slowly downstream.
In-lieu fees are allocated for regional detention facilities. In most instances, the city has found regional detention basins to function more satisfactorily than smaller, scattered on-site facilities.
Valley storage. Flood water cannot be compressed. It requires space. Encroachments into a channel or floodplain can dam, divert, or displace flood waters. So Tulsa requires compensatory excavation if a development -- including a flood control project -- would reduce valley storage. Preserving or recreating floodplain valley storage is a keystone of the city's program.
Freeboard. NFIP regulations require finished floors of new development to be at or above the base flood elevation, based on existing watershed conditions. Tulsa includes freeboard as another margin of safety, requiring finished floors to be at least 1 foot above the regulatory flood elevation, based on ultimate watershed urbanization.
Erosion and sedimentation. Erosion and sedimentation rob hillsides of valuable topsoil, dam lowlands, clog streams, and pollute rivers. Builders must control site erosion from new development.
Permits and performance standards
Tulsa requires a watershed development permit to be issued before developing, redeveloping, building, excavating, grading, regrading, paving, landfilling, berming, or diking of any property within the city. There are five types of watershed development permits: floodway, floodplain, stormwater drainage, stormwater connection, and earth change permits. Individual residential lots outside the floodplain are exempted.
Tulsa's regulations are based on adopted floodplain maps (both Tulsa and NFIP), watershed-wide master drainage plans, and development permits based on specific performance standards.
PLANNING AND CAPITAL PROJECTS
A decade ago, Tulsa faced up to its need for half a billion dollars in corrective flood projects. The city had been built, over decades, without much of a drainage system, and the result was disastrous. The task appeared overwhelming.
Since then, Tulsa has completed or underconstruction more than $200 million in capital plans and projects, including $80 million in federal funds.
The capital program includes structural, nonstructural and multi-objective projects. By combining techniques, flood hazards have been reduced for thousands of Tulsans.
More than $300 million in flood-reduction projects are still needed. Tulsa's program is still under way, and will be for years, to correct drainage problems that were created over many decades.
The backbone of Tulsa's stormwater management system is its master drainage planning. The planning process involves extensive citizen participation, including hundreds of public meetings over the past decade.
Master drainage plans. Tulsa has completed master drainage plans for virtually all drainage basins. Each plan is a comprehensive, watershed-wide study of a drainage basin that documents existing floodplain information and recommends solutions for flooding and drainage problems.
A typical master drainage plan is developed within the context of the community, and so takes into account community values, existing conditions, goals and objectives, and future plans. The result is a plan for actions and projects, including costs and benefits.
City-wide master plan. In 1989, the city synthesized its various master drainage plans into one city-wide document, The City of Tulsa Flood and Stormwater Management Plan, 1990-2005. This city-wide plan ranks and prioritizes hundreds of recommended projects, to guide capital scheduling.
Priority-setting was challenging. Citizens in every watershed faced severe flooding problems. In general, priorities are based on hazard, cost, benefit, and feasibility.
Mingo Creek project. The 61-square-mile Mingo watershed drains the eastern one-third of the city but has accounted for two-thirds of Tulsa's flood damages in recent years. The U.S. Army Corps of Engineers and the city worked together in the late 1970s to develop a plan for Mingo flood control, which Congress authorized for construction in 1986.
The Corps estimates that the completed $143 million project will prevent $32 million in average annual flood damages. With an average annual cost of about $16 million, the Mingo project has a benefit-to-cost ratio of 2 to 1.
The local cooperation agreement signed by the city helped forge new legislation, written into the Water Resources Development Act of 1986, which also gives communities credit for past construction projects. The federal government recognized that before 1986 Tulsa had constructed some Mingo channels and detention basins that were compatible with the Corps project. The federal government agreed to give the city credit toward its local share plus reimbursement for the federal share of prior expenditures that pertain to the project. Tulsa has received $10 million in reimbursements and expects to receive about $10 million more.
Acquisition and relocation. Over the past 15 years, Tulsa has cleared more than 900 buildings from its floodplains. The largest clearance came after the 1984 flood, when more than 300 single-family homes and 228 mobile homes pads were acquired and cleared.
The city's floodplain program is gradually reducing its inventory of thousands of floodprone buildings. The city is also updating its post-flood mitigation plan to include acquisition and relocation recommendations for before, during, and after a flood.
Small capital projects. Many flooding and drainage projects throughout the city are localized but troublesome. They are addressed through small capital projects, generally less than $100,000 each. Every year, $700,000 is allocated from the utility fee for small projects. Some are also funded through long-range capital sources. Floodproofing.` In some instances flood damages to existing structures can be averted by spot flood-proofing, such as elevation of the existing structure on site, shields for windows and doors, and ring levees. Oklahoma law does not allow the city to spend public funds to floodproof individual structures, so currently the city's role is limited to technical assistance to private property owners.
Stormwater quality is of growing concern in municipal drainage management. Tulsa has geared up to meet new federal requirements for stormwater discharge NPDES permits (National Pollutant Discharge Elimination System permits). Tulsa's most serious problem with runoff quality was found to be sediment, which is being addressed through vigorous regulation of erosion from construction projects. The city is also emphasizing street sweeping, environmental monitoring, and stormwater laboratory services as part of its stormwater quality program.
MAINTENANCE AND OPERATIONS
City leaders clearly saw the need for better maintenance when the 1984 flood swamped debris-choked creeks and channels, clogged and collapsed sewers, and neglected pump stations. The resulting public and private costs were enormous.
The flood triggered a search for stable, continual maintenance funding. The answer came in 1986, when city fathers approved a drainage utility fee. Now maintenance is an essential element of Tulsa's program.
The contrast is telling:
The difference was the stormwater utility fee.
The maintenance program's first goal is to keep systems operating at full capacity.
The system includes hundreds of miles of surface channels and floodplains, thousands of miles of underground sewers, public detention basins, pump stations, roadside ditches, bridges, and the curbs and inlets along the street system.
The list of duties continues to expand, extending through turf control and tree planting, debris removal, emergency response during storms, and management of maintenance trails along drainageways.
Capricious climate makes Tulsa vulnerable to weather emergencies, particularly tornadoes, violent thunderstorms, and floods.
Overall responsibility during emergencies lies with the city-county Tulsa Area Emergency Management Agency; but in flood management, TAEMA shares its lead with Tulsa's Public Works Department.
Tulsa's emergency management goal is to reduce hazard and damage before, during and after storms.
Forecasting and warning
Flash floods require the earliest possible warnings. Tulsa's system works in cooperation with the National Weather Service, news media, TAEMA, and the City of Tulsa. A computerized ALERT system includes 39 rain, 19 stream, and seven detention gauges that report changes as they happen. The system is based on detailed basin inventories and includes a hydrologic program that develops stream and flood forecasts, to be released for appropriate action before flooding occurs.
Emergency response is triggered by the possibility of severe weather anywhere in the community. Response teams are guided by detailed plans and protocols -- and their extensive field experience during emergencies. The plans also identify critical facilities with hazardous materials, vulnerable occupants, and essential community functions.
Recovery and mitigation
Traditionally, recovery meant rebuilding as fast as possible. But recurring disasters have taught Tulsans that rebuilding in kind can mean reinvesting in disaster. Tulsa today emphasizes mitigation projects, which seek to make the response to each disaster reduce future losses. For example, hundreds of flooded homes have been relocated to dry sites. In addition, the city is updating its flood-hazard mitigation plans, to include actions to be taken before, during, and after a flood.
The city pushes public information and involvement to keep citizens aware that floods frequent Tulsa, requiring prudent preparation. Diverse information pieces include flood maps, brochures, news releases, fact sheets, reports, slide shows, videos, direct mailings, displays, speeches and presentations, roadway signs, and individual contacts -- anything and everything possible to get out the word. For example, the city mails periodic notices to floodplain occupants, warning them of hazards, offering them flood preparedness tips, and urging them to buy flood insurance.
Tulsa's stormwater ordinances include requirements that full information about flood hazards must be provided by property sellers to prospective buyers, and by landlords to tenants.
PUTTING IT ALL TOGETHER: ORGANIZATION AND FINANCE
After the 1984 flood, Tulsa leaders determined that the city's drainage program was scantily funded, poorly coordinated, and largely neglected. They termed stormwater the "forgotten utility." Creating a comprehensive program was a daunting challenge, beginning with the staff estimate that some $500 million was needed for high-priority flood control. As for the full range of maintenance and other needs, no one could hazard a guess.
By 1985, Tulsa had pulled all related functions together into a new Department of Stormwater Management. By 1986, the city had levied a new stormwater utility fee to finance it.
In three successful votes in 1985, 1987, and 1990, voters handily approved more than $135 million in capital sales tax and bond funds -- including local match for the $143 million Corps of Engineers project to tame Mingo Creek.
With a change in the form of city government in 1990, the stormwater program was merged into a new Public Works Department.
Today, the program continues to progress, institutionalized in Public Works, under the executive wing of Mayor M. Susan Savage. Citizen advice is provided by the Stormwater Drainage Advisory Board, which was created after the 1984 flood. Tulsa's City Council is responsible for legislation, policy, and budgets.
The fiscal foundation of Tulsa's program is the stormwater utility fee.
The fee was calculated by determining essential program requirements, then allocating the needed charges equitably to all homes and businesses. Residents of single-family homes pay $2.58 per month. Business owners pay the same amount for every 2,650 square feet of impervious surface on their properties.
The charge is based on the theory that stormwater runs off every property in the city; dwellers on both hillside and lowland contribute runoff. Since everybody helps create the need for a floodplain and stormwater program, everybody helps pay for it. The utility fee yields about $9 million annually. The largest share goes to maintenance. The balance goes toward management, planning, public education, small capital projects, and other uses.
The utility fee is not used directly for major capital projects. Major projects are financed, instead, by general obligation bonds, sales tax revenues, and -- when available -- federal funds. Similar sources are used for master drainage planning. Other funds include fees in lieu of detention and permit fees.
From Rooftop to River: Tulsa's Approach to Floodplain and Stormwater Management