An ordinance amending Chapter 15.64 of the Metropolitan Code pertaining to low impact development practices, no adverse impact design, and associated incentives.

WHEREAS, an extensive rain event that began on May 1, 2010, caused widespread flooding throughout the area of the Metropolitan Government of Nashville and Davidson County; and

WHEREAS, the flooding resulted in substantial and tragic harm to citizens and catastrophic damage to their property; and

WHEREAS, the Metropolitan Government of Nashville and Davidson County desires to reduce the probability of its citizens being impacted by flooding during future storm events; and

WHEREAS, the Metro Council has previously limited development in the floodway and flood plain; and

WHEREAS, Low Impact Development (LID) is a comprehensive land planning and engineering design approach intended to maintain and enhance the natural hydrologies of urban and developing watersheds; and

WHEREAS, Green Infrastructure, which is an approach to stormwater management that incorporates approaches and technologies that promote infiltration, evapotranspiration and the capture and reuse of stormwater, is a primary component of LID; and

WHEREAS, LID and Green Infrastructure approaches to stormwater management are attractive and cost-effective ways to reduce the risk of flooding and enhance water quality, thereby preventing and reducing risk to human life and property; and

WHEREAS, based on the recommendations of the Mayor’s Green Ribbon Committee on Environmental Sustainability, it is a priority of the Mayor’s Office of Environment and Sustainability to increase the utilization of LID techniques on all new or significantly redeveloped sites in Nashville; and

WHEREAS, Title 15 of the Metropolitan Code of Laws grants the Department of Water and Sewerage Services the authority to promulgate and enforce rules and regulation for the implementation of Green Infrastructure techniques to address stormwater issues associated with private development.


Section 1. Chapter 15.64 of the Metropolitan Code is hereby amended by deleting Section 15.64.120 in its entirely and substituting with the following new Section 15.64.120:

15.64.120 Construction that may increase degree of flooding prohibited.

All construction, whether by private or public action, shall be performed in such a manner as to:

A. have no material increase in the degree of flooding in its vicinity or in other areas whether by flow restrictions, increased runoff or by diminishing retention capacity;

B. have no adverse impact for site design including, but not limited to, no rise in the 100 year base flood elevations on any project or development located in a documented floodplain as a result of development;

C. meet such other requirements as may be determined by the Department of Water and Sewerage Services.

The Department of Water and Sewerage Services shall promulgate regulations consistent with this section.

Section 2. Section 15.64.160 of the Metropolitan Code is hereby amended by designating the existing provisions as subsection A. and adding the following new subsection B.:

“B. Not later than August 1, 2011, the department shall develop a new volume of its Stormwater Management Manual to address best practices, incentives and implementation strategies for green/low impact stormwater infrastructure and infill development (the “LID Manual”). Such LID Manual shall be consistent with the requirements of this chapter and shall include, at a minimum, provisions addressing the following:
1. Management of floodplain development including the use of wetlands, floodplain storage, and environmental features;
2. The concept of “no adverse impact” for site design;
3. Removing barriers to the utilization of LID in existing Metro Codes and Departmental Standard Operating Procedures;
4. “In-lieu of” programs that might increase overall LID utilization on development projects within Nashville and Davidson County; and
5. Minimum floor elevation requirements for residential and nonresidential development.”

Section 3. The department shall establish a stakeholder committee to assist in development of the LID Manual. The stakeholder committee shall include, but not be limited to, professional engineers, environmental structural design professionals, department employees, a representative of the Mayor, and three members of the Metropolitan Council appointed by the Metropolitan Vice Mayor. All meetings of such committee shall be open to the public and advertised in accordance with the Tennessee Open Meetings laws. The department shall provide monthly progress reports to the Metropolitan Council until the LID Manual is complete.

Section 4. The provisions of Section 15.64.170 of the Metropolitan Code are hereby deleted in their entirely and substituted with the following:

“No new structure shall be constructed within the floodway. Notwithstanding the foregoing, a structure located in the floodway as of the effective date of this ordinance may be maintained and may be repaired in the event of a casualty loss not exceeding 50% of appraised value of improvements on the property, provided that no such existing structure located in the floodway shall be enlarged or expanded beyond its existing height or building footprint.”

Section 5. This Ordinance shall take effect from and after its enactment, the welfare of The Metropolitan Government of Nashville and Davidson County requiring it.

Sponsored by: Darren Jernigan, Mike Jameson, Jim Forkum, Jason Holleman


Introduced: November 16, 2010
Passed First Reading: November 16, 2010
Referred to: Public Works Committee
Substitute Introduced: December 7, 2010
Passed Second Reading: December 7, 2010
Passed Third Reading: December 21, 2010
Approved: December 22, 2010