On-site Storm Water Management Principles

Total Site Area (TSA) of any zoned lots will consist of development (impermeable areas), vegetative areas and on-site storm water management facilities.

Landscape Areas (LA) or design components of the landscape code become micro storm water management facilities.

Design Storms (DS) of one (1) inch of rainfall will require a 12” detention of a minimum of 3630 square feet (60.24’ x 6.24’) in size per acre or 8.3% of TSA to capture and infiltrate the water volume. (TSA x 0.083 ) (43560/12=3630. SR 3630= 60.24’ x 60.24’)

A Permeability Ratio (PR) between total site area and permeable open space of at least 30 percent. (TSA x OS= 30%)

Capture Rate (CR) of storm water shall be 30% of the Design Storm (DS =1”x 0.30)

Street and Side Buffers for storm water management, planting and screening comprising 20 percent of total site area. (TSA x .20)

Street Yard Buffers (SYB) and Rear Buffers (RB) of a minimum of 78 percent of required front or rear yard set back depth. (SYB X .78 and RSB x .78)

Total Side Buffer Width (SBW) to meet zoning standards not to exceed minimum of 20 percent of property width (PW X .20)

Vehicular Use Area (VUA) used for cars, planting and storm water management shall contain a minimum of 12 percent permeable planted area. (VUA X .12)

Street Wall (SW)  planting areas sized for building façade enhancement and roof top run off collection of a minimum width of 2/10 the height of the building. (SW= BH X .20)

Stream Bank Buffers (SBB) or Water Front Yards (WF) of a minimum depth of 50 percent of stream width. ( SW x .50) (WF x .50)

Storm water BMP’s recommended by the EPA consisting of bio-swales, planted buffers, grassed swales, sand filters, micro-detentions, infiltration trenches, irrigation cisterns, storm water chambers, porous paving, preserved forest floor, protected wetlands and constructed wetlands.

Site Design based upon low impact development strategies to achieve the proper relationship between Landscape Areas, Impermeable Areas and On-site Storm Water Management facilities.

Minimum Tree Canopy (TC) set by local zoning code shall be 30% of the development site after fifteen years or seventeen (17) replacement Class A trees (30-50’canopy size) per acre as replacement trees for trees removed for construction.

Protected trees for which a Tree Remove Permit is required are comprised of the following species and sizes set forth in the Tree Preservation Ordinance.

Parking Lot Detentions (PLD) 12” deep shall be one (1/12) twelfth the size of the UVA. (UVA x 0.083) with a containment perimeter the length (L) of the UVA.

Relevant formulas include:

• 1 Acre = 43560 SF
• 1 CY= 27CF
• 1 CF=7.48 Gallons
• 1 CY=202 Gallons   
• 1 CY=5454 Gallons
• 12 SF of DS = 1 CF  
• 432 SF of DS = 1 CY
• 1 AF=43560 CF
• 1 AF=325,851 Gallons

Definitions

Bioretention  A storm water BMP or constructed wetlands with controlled water levels, slopes, grades, inflows, outflows and vegetated planting that provide ecological services.

Buffer Yard  A planted landscaped area usually at the side or rear of development sites which are provided to separate and partially obstruct the view of adjacent land uses or properties.

Canopy Area  The total area of the site covered by tree canopy measured in square yards or acres which may be actual or projected after thirty year period of growth.

Constructed Wetland  A natural looking designed storm water storage or filtering facility with minimal slope, low elevations and limited littoral shelf depth between six (6) inches and eighteen inches (18) and not exceeding forty-eight (48) inches in which natural occurring, but artificially planted, wetland facultative plants are introduced to filter, slow and clean moving storm water that passes through the facility.

Critical Root Zone  The area of tree roots within the crown drip line. This zone is generally defined as a circle with a radius extending from a tree's trunk to a point no less than the furthest crown drip line.

D.B.H.  (Diameter-at-breast-height)  A standard measure of tree size, (for trees existing on site) and is a tree trunk diameter measured in inches at a height of 4 ½ feet above the ground.

Design Components  Sections of a landscape ordinance that make reference to specific part of a site’s geography, building lot or development property that must be designed using standards, specifications or technical requirements specified in this ordinance.

Design Manual  A companion document to a landscape code which is prepared to summarize the technical language of a landscape code or tree regulations and the administrative procedures involved with preparing landscape design and storm water plans, seeking building permits, tree removal permits, land alteration permits, and conditional use of property.   The (Design Manual) also means the 2000 Maryland Storm Water (Design Manual) Volumes I & II that serves as the official guide for storm water management principles, methods, and practices contained within this code.

Design Storm (DS)  The first flush of a five year design storm or one (1) inch of rainfall in twenty-four hours which ever is greater that will be used to size all storm water BMPs

Detention  The temporary storage of storm water runoff in a BMP with the goals of controlling peak discharge rates and providing gravity settling of pollutants.

Detention Area  An area designed for the temporary storage of a determined quantity of water that will infiltrate in, evaporate out or be consumed by plant materials consistent with natural processes.

Detention Pond (Dry Pond)  A facility that provides storm water quantity control by containing excess runoff in a detention basin, then releasing the runoff at allowable levels.

Developed Site Area Open Space  The gross site area of any lot, building site or mapped segment of a multi-project tract for which a project is being planned, built or renovated.

Discharge  Flow of surface water in a stream or canal or the outflow of groundwater from a flowing artesian well, ditch, or spring. Can also apply to discharge of liquid effluent from a facility or to chemical emissions into the air through designated venting mechanisms.

Discharge Area  The outflow point of water from a project site or drainage basin on a development site.

Disconnected Roof Top  Is a term used to note that rain falling on a roof  is ‘disconnected’ from site run off by capturing it at the base of buildings.

Drainage area  An area contributing runoff to a single point measured on a horizontal plane, which is enclosed by a ridge line or drainage barrier such as a building.

Dry Well  Vertical French drains that can be drilled and filled with porous materials that will absorb storm water in areas with low water table levels. These are particularly useful to collect rain water off of roof tops and paved parking surfaces.

Facultative Plants  Native plants likely to occur in wetlands or non-wetlands (estimated probability 34%-66%) but are not necessarily recognized indicators of either wetland or upland conditions. 

Filtration  A water treatment process for removing solid (particulate) matter and other pollutants from water by means of porous media such as sand, a man-made filter, of vegetation

French Drains (infiltration trenches) (infiltration columns) Decoratively designed excavated trenches or drilled columns between six (6) inches and forty-eight (48) inches depth filled with sand and gravel to promote underground storage and infiltration of a defined minor amount of storm water.

Foundation Wall Planting Area  A proscribed area of ground of a certain length and width immediately adjacent to a building wall that separates the building from a parking lot or vehicular use area and is planted with vegetation.

Frontage (Public Street)  The horizontal distance between the side lot lines measured at a point where the side lot lines intersect the street right-of-way. All sides of a lot that abuts a street shall be considered frontage. On curve-linear streets, the arc between the side lot lines shall be considered frontage.

Ground Cover  The material planted in such a way as to form a continuous cover over the ground that can be maintained at a height not more than twelve inches.

Habitat Protection Areas (HPA)  An area identified on an approved site plan containing native vegetation, natural features or unique habitat which will remain undisturbed and capable of infiltrating storm water when the property is fully developed.

Hydro-zone  A portion of the landscaped area having plants with similar water needs that are served by one irrigation valve and a set of heads with the same schedule of water flow and timing.

Improved Soils (filtration media)  Columns of soil in twelve (12) inch lifts composed a surface growing medium composed of sand, sandy loam topsoil and organic matter over a porous base consisting of sand, fine aggregates, medium aggregates, and course aggregate. This improved soil mix is used to replace excavated slowly impermeable clays and silty clays for the purpose of increasing ground percolation rate.

Infiltration  The penetration of water through the ground surface into sub-surface soil. The technique of applying large volumes of waste water to land to penetrate the surface and percolate through the underlying soil.

Infiltration Trenches (French Drains)  Linear excavations of a designed width, depth and volume that are backfilled with irregular sized stone and sand capable of absorbing and infiltrating storm water into sandy substrata.

Irrigation Cisterns  Above ground or below ground rainwater harvesting and storage vessels in which roof water or parking lot water or domestic grey water is stored, filtered and mechanically pumped through an underground irrigation system with a GPM flow rate sufficient for the purpose of sprinkling lawn grass or shrubs beds for the purpose of disposal and horticultural service.

Irrigation system  A device or combination of devices having a controller, tap in, hose, pipe, valves, head or other features connected through which water, or a mixture of water and chemicals, is drawn and applied for residential or commercial purposes.

Impervious Surface  Land area covered by a surface treatment such as concrete, asphalt, paving, building slabs or compacted stone that hinders the ability of the underlying soils to percolate water.

Landscape  Any combination of living plants (such as turf grass, ground cover, shrubs, vines, hedges, or trees) and nonliving landscape material (such as rocks, pebbles, sand, mulch, walls, fences, or decorative paving materials) that are designed for practical drainage or aesthetic effects.

Landscape Architect  Professionally educated and licensed designer who is authorized to provide landscape architecture design services that include the preparation of landscape plans, irrigation plans, on site storm water management plans, specifications, estimates project management services and provide expert testimony in regards to site development and compliance with municipal landscape regulations.

Landscape Code  Created as a result of a landscape ordinance to set forth design components and technical standards as well as responsibilities which are included within a municipal zoning ordinance.

Landscape Plan  The preparation of graphic and written criteria, specifications, and detailed landscape plans to arrange and modify the effects of natural features such as plantings, ground and water forms, circulation, walks, irrigation, landscape lighting, erosion control, site drainage and other features to comply with the provisions of a community landscape code. Prepared and sealed by registered landscape architects to comply with the provisions of the (Unified Development Code).

Landscape Strips  Is a planted landscaped area of a proscribed width and length which separates any two use areas on development site.

Micro-detention (Rain Garden) (Rain Groves)  A shallow circular or informally designed depression less than twenty-four (24) inches deep that is natural or designed with vegetative coverage, improved soil structure, improved percolation rates that can be used to capture, and slowly infiltrate minor storm water amounts directly into sub soils.

Mulch  Nonliving; organic or synthetic materials customarily used in landscape design to allow infiltration, retard erosion and retain moisture.

Native Plant Community  A natural association of plants dominated by one or more prominent native plant species growing in its natural habitat and under natural drainage conditions.

On-site Storm water Management  The design, arrangement and construction of natural systems augmented with structures and devices that can be used to control storm water within an immediate development site while retaining a proscribed percentage of site storm water.

On-site Storm water Storage System  One, or combination of, micro-detention depressions (rain gardens), planted buffers, French drains, sand filters, vegetated swales, porous paving, underground storage chambers, pipes, vaults irrigation cisterns or other fixed containers used, or designed to be used, for capture and infiltration of on-site storm water.

On-site Storm Water Management Plan  A set of drawings or other documents submitted by a Landscape Architect, Civil Engineer or Architect as a prerequisite to obtaining on-site storm water management facilities approval. This plan contains all of the information and specifications pertaining to on-storm water management and non-structural storm water best management practices.

Open Space  The unoccupied portion of a lot or building site that is open to the sky.

Open Space Ratio (OSR)  The gross area of all pervious area on a site divided by the lot area. It may also be a proscribed percentage of open space and pervious area as set forth in community landscape codes.

Outdoor Storage Area  Sometimes called lay down areas, these spaces are uncovered areas used for storage of equipment, materials, goods, and supplies including the keeping of automobiles, trucks, boats, trailers, buses, and lawn and garden equipment which are not enclosed within building walls. Under some conditions can also be used for storm water management.

Parking Bay A defined number of parking stalls separated by interior landscape islands, plantings, storm water catchments or shade trees.

Parking Lot Detentions  Decoratively and functionally designed level to nearly level planted areas between an average depth of twelve (12) inches and thirty six  (36) inches that may be used for multiple purposes including overflow event parking, storm water infiltration or ornamental plantings of trees, shrubs, grasses and or other ground cover plants to detain, infiltrate and transpiration of minor storm water flows from vehicular use areas.

Permeable Pavement  An area of a vehicular use area paved with material that permits water infiltration into the soil.  Permeable pavement may consist of any porous surface materials that are installed, laid or poured.

Permeability Ratio (PR)  The ratio of the development foot print to the total of all open space, planted spaces, permeable soils and un-built upon land capable of infiltrating water through porous paving or natural soils.

Pervious Area  The area of a development site remaining after the area of structures, paved vehicular use areas, and impervious site service areas, access ways, contiguous pedestrian pavement system or are subtracted. Impervious surfaces are just the opposite.

Planted Storm Water Buffers  Decorative and functionally planted buffers as defined in the Landscape Code for street yard, side yard and rear yard buffers as may be required. Buffers that are used to infiltrate minor storm flows must be designed shall have the minimum width dimension of twenty (20) feet with inflow and overflow capability.

Porous Paving  Any natural, mineral, precast, poured in place, decorative stone or other surface material appropriately designed with percolation capability to increase the permeability ratio (PR) of any development site.

Preserved Forest Floor  Any preserved and protected remnant forested area or tree grove over one thousand (1000) square feet.

Preserved Wetlands  Natural drainage detentions that are heavily vegetated that are preserved and maintained on development sites to capture, detain, filter and infiltrate storm water prior to its introduction to a surface water body.

Protected Tree  A tree of a certain size, species, age or character which can not be removed from a development site without a tree removal permit.

Protective Barrier Plantings   Low evergreen shrub plantings a minimum width of thirty-six (36) inches that are used to prevent human accidental access to storm water facilities detaining or retaining more than six (6) inches of rain water. 

Rain Gardens  Small irregular depressions or concave land forms under 20 feet in diameter that can be constructed and planted within grassed lawns or un-paved areas that can be used to infiltrate storm water.

Rain Grove  A circular or irregular depression or concave land form over 40 feet in diameter that that is planted with wetland tolerant trees or wetland understory plants that can be used to detain or trap storm water.

Reclaimed Water or Grey Water  Captured run off from roof tops and irrigation cisterns are considered reclaimed water.

Retained Natural Wetlands (Grasses Wetlands) (Treed Wetlands)  Any natural drainage area, swale, marsh or swamp consisting of existing or supplemental jurisdictional wetland plants protected by Federal law.

Retention  The process of collecting and holding surface and storm water runoff with no surface outflow. The amount of precipitation on a drainage area that does not escape as runoff.

Retention Pond (Wet Pond)  A facility that treats storm water by utilizing a permanent pool of water to remove conventional pollutants from runoff through sedimentation, biological uptake and plant filtration.

Run Off  That part of precipitation, snowmelt, or irrigation water that runs off the land into streams or other surface water. It can carry pollutants from the air and land into receiving waters.

Right-of-Way  A strip of ground dedicated by the project developer for public use, title to which shall rest in the public for the purpose stated in the dedication. The most common right-of-way is for public streets but may include storm water management facilities and street side tree plantings.

Sand Filters  Designed and constructed flow through sand lens of a designed and calculated size and dimension where natural subsoil have been removed and replaced with sands and gravels capable of absorbing minor flows of natural rain water.

Secondary Elevation  A building wall used for drive through service and its immediate  planted area.

Sediments  Soils, sand, and minerals washed from land into water, usually after rain.

Shrub  A woody perennial plant differing from a perennial herb by its persistent and woody stems, and from a tree by its low stature (generally obtaining a height less than eight (8) feet) and its habit of branching from the base.

Sight Triangle  A triangular area formed by a diagonal line connecting two (2) points, located on intersecting right-of-way lines (or a right-of-way line and the curb or a driveway).

Sign Monument Zone  An area of a site dedicated or permitted to the erection of a permanent sign or sign cluster often lighted and planted with low brightly colored seasonal flowers.

Site Capture Rate (CR)  The obverse of run off and shall mean a percentage of the design storm that is captured, filtered, cleaned, infiltrated, evaporated, harvested, transpirated or stored on site with the use of the designed storm water BMPs.

Storm Water BMP (storm water best management practices)  Measures, or designed facilities that involve the use of vegetation or soil based strategy, practice, technology, process or program, or other method intended to capture, infiltrate, evaporate, transpire, and control storm water on individual development sites.

Stream Bank Buffer (Riparian Buffer)  A preserved natural vegetated buffer or reconstructed vegetative buffer of a proscribed width, use, and character along the edge of a scenic river, natural stream, bayou, pond or lake directly connected to drinking water storage facilities or  natural fresh systems of the State of Louisiana or of the United States.

Street Tree Planting Area  The street tree planting area is the area of a development site that lies between the street right-of-way line and the edge of the street curb parallel to the street.  This land is publicly owned but is often used for street tree planting, public utilities and street maintenance but can be used for storm water management. It may also include public space within the center of boulevard medians fronting development sites.

Street Wall Planting Area  A space to be planted of a proscribed dimension attached to the building wall fronting a public street that may contain underground storage or cistern storage of roof runoff that may be reclaimed for beneficial use such as irrigation.

Street Yard  An area of a development site containing plant materials and or water management facilities with a defined depth attached to a front property or servitude line which lies between the street right-of-way line and the actual front wall line of the building facing a public street. A variant is the ‘preserved street yard’ in which native trees and shrubs or all trees of a proscribed size must be preserved.

Swales (grassed swales)  (bio-swales)  Decoratively and functionally designed and appropriately sloped surface conveyance channels between six (6) inches and forty-eight (48) inches depth planted with grasses, sedges, rushes or  facultative plants to slow, filter and transpire minor storm water flows on their way to the point of infiltration, storage or disposal.

Technical Standards  Criteria, requirements, and standards, usually specified in quantities, dimensions, sizes, qualities and performance outcomes and spelled out in a landscape code to guide designers in the proper landscape design of various parts of the development site, building lot or property. 

Total Caliper Inches (TCI)  Is a measurement of urban forest canopy on an existing development site prior to seeking a clearing or building permit. Also, can mean a measure or standard for trees to be planted to replace trees removed for construction.

Travel Lane  The main access way, one way or two ways, which serves as the organizing feature of a vehicular use area or parking lot. Related features include bays, stalls, islands, peninsulas, medians, standing areas, articulated cross walks, planters, bio-swales and drainage, irrigation and lighting features.

Tree Grove  A contiguous grouping of trees of various sizes and species living in a natural habitat.

Tree Protection Area (TPA)  Any portion of a site wherein are located numerous existing trees and other native plant materials which are proposed to be preserved during construction by the erection of a proscribed type of protective fencing.

Trees  Any woody self-supporting plant characterized by having a single or multiple trunk over ten (10) feet in heigh and shall be native or well adapted species as set forth in the book Odenwald, N. Turner, J., Southern Plants For Landscape Design, Claitor’s Publications, Baton Rouge, LA, latest edition.

Tree Class “A” is any woody plant that normally grows to an overall height of at least fifty (50) feet.

Tree Class “B” is any woody plant that normally grows to an overall height of at least twenty-five (25) feet.

Tree Class “C” is any woody, large shrub like plant, of a species which normally grows with multiple stems to an overall height between ten (10) and twenty-five (25) feet.

Underground Storm Water Storage Chambers  Manufactured receptacles or site built drainage facilities that are used for storm water management purposes.

Utility Service Area  An area, often a site service area that contains any surface mounted HVAC equipment, utility boxes, booster stations, switch boxes, irrigation controllers and transformers that are part of a site utility system.

Vehicular Use Area  All areas subject to vehicular traffic including access ways, driveways, loading areas, service areas, vehicular display areas and parking stalls for all types of vehicles. Common examples include parking lots, driveways, alleys, automobile display areas and interior streets on private development.

Vehicular Use Area Detention see Parking Lot Detention.

Vehicular Use Area Interiors  Shall consist of planting and storm water capture areas within islands, peninsulas, medians, vegetated swales and parking bays that are used to separate parking areas and travel lanes and to organize automobile and pedestrian travel.

Vehicular Use Area Screen  Any planting, wall or fence with a minimum opacity of 75% installed or growing to a minimum height of  thirty-six (36) inches for the purpose of screening views of parked cars front public streets or low intensity land uses.

Visual Screen  A physical obstruction, partially opaque, consisting of living plant material, natural or manmade construction material, or a combination thereof used to visually separate two areas of a building site or adjacent building sites.

Water Management Areas   Shall mean all parcels of the site set aside by this code in which on-site storm water facilities such as underground chambers, detentions, infiltrations, filters, detentions, preserved wetlands and habitats share space with landscaping. Water management areas shall be inspected monthly and annually and maintained and repaired as needed.

Watershed  The land area that drains into a stream; the watershed for a major river may encompass a number of smaller watersheds that ultimately combine at a common point. At the larger scale, East Baton Rouge Parish is the Lake Pontchartrain Basin (watershed) and one-third of the U.S. drains into the Atchafalaya Basin (watershed).

Wetland Plants  Plants normally growing within areas of saturated soils during a identifiable period of time each year and as recognized by the U.S. Army Corps of Engineers, New Orleans District in the document Wetland Plants of the New Orleans District, 1977.