Orleans and Jefferson Parishes

Stormwater BMP Guidance Tool: A Stormwater Best Management Practices Guide for Orleans and Jefferson Parishes

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Guidance tool for two parishes (county-level), not a binding design ordinance. No uniform WQv; cites City of New Orleans 10-year/24-hour and Jefferson Parish 10-year peak-match as local examples. SWMM/HSPF are evaluation tools, not required software.

Fields not found in document: design_criteria.required_hydrologic_hydraulic_software

Other manuals in Louisiana: City of Baton Rouge / East Baton Rouge Parish

Document Metadata

Jurisdiction level

county

“Guide for Orleans and Jefferson Parishes”
Title Page

State

Louisiana

“funded by a federal grant administered by the Louisiana Department of Environmental Quality (LDEQ)”
Acknowledgements

Version / edition

October 2010

“October, 2010”
Title Page

Adoption / effective date

2010-10

“October, 2010”
Title Page

Last revised date

2010-10

“Bayou Land RC&D iv October 2010”
Acknowledgements footer

Relationship to state manual

independent

“Bayou Land contracted Geosyntec Consultants to develop the guidance manual.”
Acknowledgements

Design Criteria

Design storm return periods (years)

10-year, 100-year

“Jefferson Parish requires that post-development runoff may not exceed that of the pre-construction state for the 10-year return event.”
Section 2.5.3 Local Regulations

Water quality volume method

No single parish-wide water quality volume is mandated. Guidance notes other cities require first-inch rainfall capture or matching pre-construction runoff volume, but recommends a minimum volume-reduction goal of matching average annual predevelopment evapotranspiration for Orleans/Jefferson redevelopment constraints. BMP sizing uses a water quality design volume; design storm depth can be back-calculated from that volume (d = V × 12 / [C × A × 43560], C = 0.05 + 0.9 × imp). Performance is evaluated via percent volume capture, with continuous simulation (e.g., EPA SWMM) preferred for accurate estimates.

“A number of cities in the United States require the collection of a specific volume of runoff such as the first inch of rainfall... A reasonable minimum goal for volume reduction would be to match the average annual predevelopment evapotranspiration volume for the site.”
Section 2.1.1 Volume Reduction Objective

Peak flow calculation method(s)

Rational Method, Unit hydrograph methods, SCS curve number method, SCS Type III dimensionless hyetograph (New Orleans area), Continuous simulation (SWMM, HSPF)

“Design flow rates are typically determined using unit hydrograph, rational method, or SCS curve number approaches for computing peak flow rates from the drainage area.”
Section 4.1, Flow-Based BMPs

Required hydrologic/hydraulic software

Not found in document

No evidence cited

Approved BMP categories

Site Design BMPs, Biofiltration BMPs (Rain Gardens/Bioretention, Vegetated Swale Filter, Vegetated Filter Strip), Permeable Pavement and Media Filtration BMPs (Porous Asphalt/Concrete/Pavers, Gravel Trenches, Sand Filters), Building BMPs (Cistern/Rain Barrel, Planter Box, Green Roof), Retention and Detention BMPs (Constructed Treatment Wetland, Wet Retention Basin, Dry Extended Detention Basin)

“3.1 Site Design BMPs... 3.2 Biofiltration BMPs... 3.3 Permeable Pavement and Media Filtration BMPs... 3.4 Building BMPs... 3.5 Retention and Detention BMPs”
Table of Contents / Chapter 3