Drainage Design Manual

The Mohave County Board of Supervisors approved and adopted BOS Resolution 2014-050 on May 19th, 2014, amending the existing Mohave County Drainage Design Manual for addressing drainage design and storm water mitigation associated with development projects under the Mohave County Land Division Regulations and Zoning Regulations.

The Drainage Design Manual is a “state-of-the-art” engineering manual that incorporates the most up-to-date and scientifically proven design methods. The addition of the Drainage Design Manual to the County’s design standards provides the technical basis for sound storm water management.

The Drainage Design Manual for Mohave County will also supplement the Land Division Regulations by providing minimum requirements and guidelines for addressing storm water issues associated with new and existing development. An additional purpose is to provide guidance and detail for implementation of the Flood Control District’s Floodplain Ordinance. It is intended that drainage studies, plans, design reports, construction drawings and accompanying drainage/floodplain use permit applications are prepared in accordance with the philosophies policies and minimum standards contained in the manual.

This will greatly enhance the quality and standardization of engineering submittals and expedite the review, permitting and approval process.

It is the intent of Mohave County to have a comprehensive storm water management program that protects the health, safety and welfare of its citizens, their property, and the environment.
 
The County's storm water management documents include the Mohave County Flood Control Ordinance (2023), the Mohave County Land Division Regulations (2021), the Mohave County Zoning Ordinance (2024) and the Drainage Design Manual for Mohave County (2022).

The purpose of the Drainage Design Manual for Mohave County (DDM) is to supplement the listed regulations and ordinances by providing additional criteria for addressing storm water issues associated with new and existing development. The DDM contains drainage philosophies, policies, and minimum technical standards. It is intended that drainage studies, plans, design reports, construction drawings and accompanying drainage/floodplain use permit applications, prepared in accordance with the DDM, will meet the minimum requirements of the governing ordinances and regulations. This manual provides a convenient source of technical information that is specifically tailored to the unique hydrologic, environmental and social character of Mohave County; and a consistent set of criteria that, when used by the local governing agencies and the land development community, will result in uniform drainage practices throughout the County.

The DDM is intended to be used in conjunction with the Drainage Design Management System (DDMS) for Windows software. This software is available to the citizens of Mohave County at no charge and has been tailored for use in Mohave County.

DDMS computer program referenced in the DDM is available below for download and installation.  Also available is an ESRI GIS shape file of the NRCS soils information for Mohave County watersheds and DDMS examples in PKZIP format that correspond with the examples in the DDM.  The example PKZIP files may be directly imported into DDMSW using the "File: Project Management: Import Project" option in DDMS.  Also available are ESRI Arc Info ASCII Grid files of the NOAA Atlas 14 point precipitation data.

• Drainage Design Manual (DDM) 3.1 (Updated 2022)
• Drainage Design Manual Appendices
  • Appendix E: Checklists
  • DDM Checklist 1: Drainage Design Report Checklist
  • DDM Checklist 2: Hydrology Specific Checklist
  • DDM Checklist 3: HEC-RAS Hydraulics Specific Checklist
  • DDM Checklist 4: Technical Data Notebook Checklist
• Drainage Design Manual Software (DDMS)(Version 4.5.0) 
  • DDMS Patch (Version 4.5.1)
  • DDMS Installation Instructions
• Soils Full DB (Full Database) 2018
• Soils SA1 DB 2018
• Soils SA2 DB 2018
• Soils SA3 DB 2018
• Soils SA4 DB 2018
• Soils SA5 DB 2018
• Soils LID DB 2018
• Soils Shape File Naming Convention Descriptions
• Rainfall Archive
• NOAA14 Maps DEM
• Mohave Rational Method Example Archive
• Mohave Unit Hydrograph Method Example Archive