Stormwater Management Plan, Page 2
Planning and Capital Projects
A decade ago, Tulsa faced up to its need for $500 million 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 has under construction 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.
Planning
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.
Capital projects
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.
Tulsa's Stormwater Management Plan, Page 3