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DAB 103 - Drainage Basin Planning Study

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There are four levels of drainage planning.

The initial plan is the Drainage Basin Planning Study (DBPS), which is governed by broad general framework goals.

Next is the Master Development Drainage Plan (MDDP) which provides greater hydrologic and hydraulic detail as well as adhering to the requirements of the Drainage Basin Planning Study. A Master Development Drainage Plan is typically the first drainage submittal required for a comprehensive development plan.

In addition to an MDDP, each new development must provide a Preliminary and Final Drainage Report. Each of these levels of drainage planning is defined as follows.

 Drainage Basin Planning Study

A Drainage Basin Planning Study is an engineering and planning study of a drainage basin which is tributary to a major receiving stream. A DBPS shall show the conduits, channels, natural drainage courses, detention reservoirs, easements, culverts and all other hydraulic facilities required to control surface waters from the 100-year event within said basin and to carry such waters to points of insignificant impact. Subbasins shall be delineated.

The study shall include an estimate of the cost of said drainage facilities, the computation of such cost may include the expense of the study. The drainage fee is intended to represent the equitable share of the cost of drainage facilities to be constructed and is expressed in dollars per acre. 

The estimated cost per acre of providing said facilities shall generally be determined within each drainage basin by dividing the number of developable acres within the basin into the total cost of improvement. City participation in funding shall be determined by the City Council and shall consider recommendations by the Storm Drainage Board. This per acre cost shall be known as the unit drainage fee. This unit drainage fee concept is described in the City’s Subdivision Policy Manual. 

Master Development Drainage Plan

A snapshot of the drainage basins in the southwestern part of the CityFigure 1: A snapshot of the drainage basins in the southwestern part of the City.

 A Master Development Drainage Plan will be prepared for developments within any drainage basin. The purpose of the MDDP is to complete drainage planning for the pro-posed development before embarking on individual phases. 

Site requirements including public improvement for the development will be identified in the MDDP. The MDDP must identify hydrology and hydraulics of existing/proposed drainage ways and appurtenant structures that are within or  effect a proposed development.

This hydrology should be compatible with the DBPS. Changes proposed by the MDDP, must be analyzed within the context of the DBP to determine impact on downstream users.

The MDDP must describe the general treatment of drainage ways, including safety and maintenance. The plan outlines the protection of public facilities, such as bridge crossings and utilities, and the protection of private property adjacent to the banks of the drainage ways.

Rights-of-Way requirements must be delineated on the plans for all drainage ways, storage facilities and other drainage structures. A Master Development Drainage Plan shall be required for any phased development greater than 10 acres prior to approval of land annexation, or preliminary plat/plan. 

Preliminary Drainage Report

The purpose of a Preliminary Drainage Report (PDR) is to identify and propose specific solutions to drainage problems that would occur as a result of that portion of the development considered for platting. Detailed analysis of drainage basin hydrology and hydraulics is required.

Alternative solutions to drainage problems shall be noted and the capacity of drainage facilities on and off-site shall be evaluated. Specific improvement, including open channels, storm sewers, grading, site stabilization, catch basins, culverts and other improvements will be located and sized to meet requirements of the initial and major drainage system.

See the City’s Subdivision Policy Manual for submittal requirements.

A snapshot of the drainage basins in the northeastern part of the City.

Figure 2: A snapshot of the drainage basins in the northeastern part of the City.

Final Drainage Report

The purpose of a Final Drainage Report (FDR) is to analyze all drainage features of the proposed platted development in the detail necessary to complete construction plans for all project drainage structures, including grading, streets, and off-site facilities, as applicable.

Terminology

Hydraulics

A branch of engineering that focuses on the practical problems of collecting, storing, measuring, transporting, controlling, and using water.

Hydrology

Hydrology is involved with the distribution, circulation and occurrence of all waters on the Earth. It studies water's effects on Earth's atmosphere and surface and the properties of water. It includes the study of flood plains, ground and surface water runoff and precipitation.

Additional Information

Engineering Development Review