Stormwater BMP Effectiveness and the BMPTRAINS Model
Pinellas County Stormwater Management Manual Training
Workshop
BASIC PRINCIPLES FOR LOADING AND REMOVAL
• Loading depends on runoff and land use characteristics• Runoff depends on rainfall and land use characteristics• Removal depends on runoff loading and performance of BMPs • Thus must have reasonable estimates for
• Rainfall• Runoff• Concentrations of pollutants in the runoff• Performance of BMPs and LIDs as individual units and in combination with others• Cost of the BMPs and LIDs.
RAINFALL CHARACTERISTICSPINELLAS COUNTY HISTORICAL DATA
• A predictor of the future is the past
• Rainfall data are based on an evaluation conducted by Harper and Baker (2007) for FDEP which is summarized in the document titled “Evaluation of Current Stormwater Design Criteria within the State of Florida” A extension of the original work done by FDEP in the 1970s.
• Study included an evaluation of rainfall characteristics throughout the State, including• Rainfall depths• Rainfall variability• Inter-event dry periods
METEOROLOGICAL MONITORING SITES
- DATA OBTAINED FOR 1971-2000
- 160 SITES TOTAL- 111 SITES IN FLORIDA
- 49 SITES IN PERIMETER AREAS
- OVERALL ANNUAL MEAN DEVELOPED FOR EACH
SITE
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Available Meteorological Data
- Rainfall isopleths were developed for 1971 – 2000 based
on the annual mean values
- Florida rainfall is highly variable ranging from ~ 38 – 66 in/yr,
depending on location
- Average Annual updated using up to 2014 is about 51inches and is used as rainfall in BMPTRAINS*
Average Annual Florida Precipitation 1971 – 2000
*Not available in any other models:Available from www.stormwater.ucf.edu free of charge
ESCAMBIA COUNTY AVERAGE ANNUAL RAINFALL
- Expanded view plots are available in BMPTRAINS
for the entire State
-
SIMILAR METEOROLOGICAL ZONES
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APALACHICOLA
AVON PARK
BOCA RATON
BRANFORD
BROOKSVILLE
CLEWISTON
CRESTVIEW
CROSS CITY
DAYTONA BEACHDELAND
DOWLING PARK
FORT MYERS
GAINESVILLE
GRACEVILLE
HOMESTEAD EXP STN
INGLIS
JACKSONVILLE
KEY WEST
KISSIMMEE
LAKELAND
LAMONT
LEESBURG
LIGNUMVITAE KEY
LYNNE
MARINELAND
MELBOURNE
MIAMI
MOORE HAVEN LOCK 1
NICEVILLE
ORLANDO
PANACEA
PANAMA CITY
PARRISH
PENSACOLA
RAIFORD
ST LEO
ST LUCIE NEW LOCK 1
ST PETERSBURG
TALLAHASSEE
TAMIAMI TRAIL 40 MI
TAMPA
VENUS
VERNON
W PALM BEACH
WOODRUFF DAM
50 0 50 100 Miles
N
EW
S
Clusters1
2
3
4
5
- Cluster analysis used to identify areas with similar
annual rainfall/runoff relationships (C values on an average annual basis)
- Analysis identified 5 significantly different
areas
-
ZONE 4
RUNOFF GENERATION
• Runoff generation is a function of:• Precipitation
• Volume and Intensity• Inter-event dry periods
• Soil types• Land cover
• Understanding all relationships is essential to quantifying runoff
Annual Runoff coefficients (C values) function of rain and ground conditions
• Runoff coefficients reflect the proportion of rainfall that becomes runoff under specified conditions and on annual basis.
• CN are used to reflect the runoff conditions.• Annual simulations using 45 sites in Florida.
.
Annual Runoff Coefficients (depth of runoff from rainfall in a period of time)
DIRECTLY CONNECTED IMPERVIOUS AREAS (DCIA)
Annual runoff estimation is the sum of events using separate DCIA and remaining area runoff. Example: Residential area with A type soils, 1/3 acre lots , 30% DCIA, fair grass cover:
DCIA = 30%CN pervious = 49CCN = 64
* Reference: CN method, see Hydrology, Wanielista, et.al, 1997, page 155
DCIA = 30%CN pervious = 49Do not useCCN
R does notExceed 0 until P > 1.12 inches*
At P = 1.12 inchesR= 0.3 x 1.12 = 0.34 inch And of course RunoffFor all rainfalls less than1.12 based on the DCIA*
DIRECTLY CONNECTED IMPERVIOUS AREAS (DCIA)• DCIA includes all impervious areas from which runoff discharges directly into
the drainage system during small events.• Does not include swales as DCIA or any other BMP from which a significant
(generally >4 inches) water volume is abstracted. • Disconnected if the storage (surface and ground) provides capture of
almost all rainfall events; as examples:• Intentional depression storage between parking areas ½ foot water
depth and 2 feet of select media at a water storage capacity of 0.25 = 12 inches calculation is (0.5’+2’x 0.25)x12
• Separation of at least 10 feet for overland flow in Type A soils and slope<5%
• Pervious pavements with sufficient reservoir storage to exceed 4 inches.• Separation of at least 20 feet for overland flow in other than Type A soils.
• NOTE: BMPTRAINS will adjust runoff volumes when BMPs are used. • AND WHY 4 inches? 4 inches retention results in captures > 99% volume.
Comparison of State-Wide Annual C Values forA Hypothetical Residential Development
DCIA = 40%Non-DCIA CN = 70
O.396
O.358
O.365
O.372
O.379
SUMMARY RUNOFF CONDITIONS
• Like rainfall, runoff in Florida is highly variable, depends on• Impervious area
• Direct relationship between runoff and impervious percentage• Non-DCIA CN value (soils and cover crop)
• Exponential relationship between CN value and runoff• Characteristics of rain events
• BMPTRAINS Model is the only one that calculates annual C value and runoff volume based on site and rainfall characteristics characteristics of the project site.
HOW DO WE CALCULATED THE LOADINGS
• Runoff concentrations are commonly expressed in terms of an event mean concentration (EMC):
• An annual EMC value is generally determined by evaluating event values over a range of rainfall depths and seasons• Generally estimated based on field monitoring• Usually requires a minimum of 7-10 events collected over a range of conditions
• Annual mass loadings are calculated by:
EMC = pollutant loading
runoff volume______________
Annual mass loading = annual runoff volume x EMC
HISTORY OF FLORIDA EMC DATABASE• The original database was developed by ERD in 1990 in support of the Tampa Bay
SWIM Plan• A literature review was conducted to identify runoff emc values for single land use
categories in Florida• Approximately 100 field studies were identified
• Each study was evaluated for adequacy of the data, length of study, number of monitored events, completeness, and monitoring protocol
• Selection criteria• Monitoring site included a single land use category – most difficult criterion• At least 1 year of data collection; minimum of 5 events monitored in a flow-weighted fashion• Wide range of rainfall depths and antecedent dry periods included in monitored events• Seasonal variability included in monitored samples
• 59 studies were selected for inclusion in the data base for post development• Values were summarized by land use category and includes runoff from all sources, ie
roof tops included in commercial and residential areas.• First known compilation of EMC data for Florida• EMC values calculated as simple arithmetic means
FLORIDA DEVELOPED LAND STUDIES IN EMC DATA BASE
LAND USE NUMBER OF FIELD SITES
Single Family Residential 17
Multi-Family Residential 6Low Intensity Commercial 9High Intensity Commercial 4Industrial 4Highway 15Parks/open space 4
• Runoff EMC values are available for a wide range of land use categories in Florida• Urban land uses• Natural land uses
• Estimation of annual runoff loadings requires• Estimation of annual runoff volume• Runoff EMC value which reflects ground cover runoff characteristics
• Any calculations should be based on user input data for• Location• Annual rainfall• Project physical land and soil characteristics• Pre/post Land use and cover
SUMMARY OF EMC AND LOADINGS
B Y : C L AR K H U L L , E R I C L I V I N G S T O N AN D M AR T Y W AN I E L I S T A
QUESTIONS, REMARKS AND DISCUSSION
2017Pinellas County
Pinellas County Stormwater Management Manual Training
Workshop
HOW DO WE ASSIGN EFFECTIVENESS TO THE LID BMPS IN THE COUNTY STORMWATER MANUAL?
Many reduce the volume of runoff, thus reduce TMDL1. Reduce impervious areas: These reduce the area from which there is discharge
and thus reduce the stormwater volume and the amount of mass discharged.2. Pervious pavements: Storage in reservoir resulting in a reduction in the volume
of discharge which reduces the pollutant loading.3. Bioretention areas: promotes infiltration resulting in a reduction in volume
discharge and pollutant loadings.4. Swales: transport and infiltrate stormwater, thus a reduction in volume of
discharge and pollutant loadings.5. Vegetated greenroofs, promotes evapotranspiration and thus a reduction in the
volume of discharge and pollutant loadings.
THREE LID RETENTION OPTIONS PERVIOUS PAVEMENTS, SWALES, AND RAIN GARDENS
All three together
Note: greenroofs also retain about 0.1 inch of water per inch of media depth
Street and Parking Lot Depression Areas or Rain Gardens
• An evaluation of the efficiency of retention practices was conducted by Harper and Baker (2007) for FDEP which is summarized in the document titled “Evaluation of Current Stormwater Design Criteria within the State of Florida”
• Based on a continuous simulation of runoff
RETENTION EFFICIENCYWITH APPLICATION TO PERVIOUS PAVEMENTS AND BIO-RETENTION
Bioretention area in pervious parking lotat Central Office Complex
Modeled Dry Retention Removal Efficiencies
Source: Harper and Baker (2007) - Appendix D
Tables were generated of retention efficiency for each meteorological zone in 0.25 inch intervals from 0.25 - 4.0 inches - 16 separate tables per zone
NDCIA 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0 55.0 60.0 65.0 70.0 75.0 80.0 85.0 90.0 95.0 100.0
30.0 94.00 94.20 92.10 88.80 84.80 80.50 76.30 72.40 68.60 65.20 62.00 59.10 56.40 53.90 51.70 49.50 47.60 45.80 44.10 42.6035.0 91.10 92.30 90.70 87.70 84.00 79.90 75.90 72.00 68.40 65.00 61.90 59.00 56.30 53.90 51.60 49.50 47.60 45.80 44.10 42.6040.0 87.80 90.00 88.90 86.40 82.90 79.10 75.30 71.50 68.00 64.70 61.60 58.80 56.20 53.80 51.50 49.40 47.50 45.70 44.10 42.6045.0 84.00 87.20 86.80 84.70 81.60 78.10 74.50 70.90 67.50 64.30 61.30 58.60 56.00 53.60 51.40 49.40 47.50 45.70 44.10 42.6050.0 79.90 84.00 84.30 82.70 80.10 76.90 73.50 70.20 66.90 63.90 61.00 58.30 55.80 53.50 51.30 49.30 47.40 45.70 44.10 42.6055.0 75.60 80.40 81.40 80.40 78.20 75.40 72.30 69.20 66.20 63.30 60.50 57.90 55.50 53.20 51.10 49.20 47.30 45.60 44.00 42.6060.0 71.30 76.50 78.10 77.60 75.90 73.60 70.90 68.00 65.20 62.50 59.90 57.40 55.10 53.00 50.90 49.00 47.20 45.60 44.00 42.6065.0 67.10 72.40 74.40 74.50 73.30 71.40 69.10 66.60 64.10 61.60 59.20 56.90 54.70 52.60 50.60 48.80 47.10 45.50 44.00 42.6070.0 63.00 68.10 70.30 70.80 70.20 68.90 67.00 64.90 62.70 60.50 58.30 56.10 54.10 52.10 50.30 48.60 46.90 45.40 43.90 42.6075.0 59.20 63.70 65.90 66.70 66.60 65.70 64.40 62.70 60.90 59.00 57.10 55.20 53.30 51.50 49.80 48.20 46.70 45.20 43.80 42.6080.0 55.80 59.40 61.40 62.30 62.40 61.90 61.10 59.90 58.60 57.10 55.50 53.90 52.30 50.70 49.20 47.80 46.40 45.00 43.80 42.6085.0 52.70 55.20 56.70 57.50 57.70 57.60 57.10 56.40 55.50 54.50 53.30 52.10 50.80 49.60 48.30 47.10 45.90 44.70 43.60 42.6090.0 49.70 51.10 52.00 52.50 52.80 52.80 52.60 52.20 51.70 51.10 50.30 49.60 48.70 47.90 47.00 46.10 45.20 44.30 43.40 42.6095.0 46.70 47.10 47.40 47.50 47.60 47.60 47.50 47.30 47.10 46.80 46.50 46.20 45.80 45.40 44.90 44.50 44.00 43.50 43.00 42.6098.0 44.90 44.90 44.80 44.80 44.70 44.70 44.60 44.50 44.30 44.20 44.10 44.00 43.80 43.60 43.50 43.30 43.10 42.90 42.70 42.60
NDCIA 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0 55.0 60.0 65.0 70.0 75.0 80.0 85.0 90.0 95.0 100.0
30.0 95.60 96.40 95.60 94.10 92.10 89.60 86.80 83.90 81.00 78.10 75.30 72.70 70.10 67.70 65.40 63.30 61.20 59.30 57.40 55.7035.0 93.50 94.90 94.50 93.20 91.30 89.00 86.30 83.50 80.70 77.90 75.10 72.50 70.00 67.60 65.40 63.20 61.20 59.30 57.40 55.7040.0 91.00 93.10 93.00 92.00 90.30 88.10 85.70 83.00 80.20 77.50 74.90 72.30 69.80 67.50 65.30 63.10 61.10 59.20 57.40 55.7045.0 88.10 90.90 91.30 90.50 89.10 87.10 84.80 82.30 79.70 77.10 74.50 72.00 69.60 67.30 65.10 63.00 61.10 59.20 57.40 55.7050.0 85.00 88.40 89.20 88.80 87.60 85.90 83.80 81.50 79.00 76.50 74.10 71.70 69.30 67.10 65.00 62.90 61.00 59.10 57.40 55.7055.0 81.70 85.70 86.80 86.80 85.90 84.50 82.60 80.50 78.20 75.90 73.50 71.20 69.00 66.80 64.80 62.80 60.90 59.10 57.40 55.7060.0 78.40 82.60 84.10 84.40 83.90 82.70 81.10 79.20 77.20 75.00 72.80 70.70 68.60 66.50 64.50 62.60 60.80 59.00 57.30 55.7065.0 75.00 79.30 81.10 81.70 81.50 80.70 79.40 77.80 76.00 74.00 72.00 70.00 68.00 66.10 64.20 62.30 60.60 58.90 57.30 55.7070.0 71.70 75.90 77.90 78.70 78.70 78.20 77.30 76.00 74.40 72.70 71.00 69.10 67.30 65.50 63.80 62.00 60.40 58.80 57.20 55.7075.0 68.70 72.50 74.40 75.40 75.60 75.30 74.70 73.70 72.50 71.10 69.60 68.00 66.40 64.80 63.20 61.60 60.10 58.60 57.10 55.7080.0 65.90 69.00 70.80 71.70 72.10 72.10 71.70 71.00 70.10 69.00 67.80 66.60 65.20 63.90 62.50 61.10 59.70 58.30 57.00 55.7085.0 63.50 65.70 67.10 67.90 68.30 68.30 68.10 67.70 67.10 66.40 65.50 64.60 63.60 62.50 61.40 60.30 59.10 58.00 56.80 55.7090.0 61.20 62.40 63.20 63.80 64.10 64.20 64.10 63.90 63.60 63.20 62.70 62.10 61.40 60.70 59.90 59.10 58.30 57.40 56.60 55.7095.0 58.70 59.10 59.40 59.60 59.70 59.70 59.70 59.70 59.50 59.40 59.10 58.90 58.60 58.20 57.90 57.50 57.10 56.60 56.20 55.7098.0 57.50 57.50 57.50 57.50 57.50 57.40 57.40 57.30 57.20 57.10 57.00 56.90 56.80 56.60 56.50 56.40 56.20 56.00 55.90 55.70
Percent DCIA
Percent DCIA
Mean Annual Mass Removal Efficiencies for 0.75-inches of Retention for Zone 4
Mean Annual Mass Removal Efficiencies for 0.50-inches of Retention for Zone 4
Retention Depth Required for 80% RemovalState-wide Average
RETENTION EFFECTIVENESS FUNCTION OF DEPTH: EXAMPLE 1.5 INCHES CAPTURE
0
10
20
30
40
50
60
70
80
90
100
0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00
Trea
tmen
t effi
cien
cy(%
):
Retention depth (inch):
Efficiency Curve: System Efficiency (N $ P) CAT 1:System Efficiency (N $ P) CAT 2: System Efficiency (N $ P) CAT 3:System Efficiency (N $ P) CAT 4:
Going from a residentialArea to a multifamily areawith net improvement andsandy soils, need 68% TN and 77% TP removal.
Result using BMPTRAINS80% removal for 1.5 inchDepth of treatment.
EXAMPLE OUTPUT GREENROOF DESIGN(USING BMPTRAINS SCREEN CAPTURE)
2 inches of cistern storagePinellas County location With 51 inches of rain /year
45
50
55
60
65
70
75
80
85
90
95
0.50 1.50 2.50 3.50 4.50Re
tent
ion
effic
ienc
y (%
):
Retention depth (inch):
Efficiency Curve (N $ P) Sys Eff (N $ P) CAT 1 Sys Eff (N $ P) CAT 2
Sys Eff (N $ P) CAT 3 Sys Eff (N $ P) CAT 4
SAVE THE SWALES
GRAPH TO AID IN SPACING80% Capture
5% slope
Downstream Upstream
PROGRAMMING OF EQUATIONS( AN EXAMPLE)
EXAMPLE OUTPUT SWALE DESIGN(SCREEN CAPTURE FROM BMPTRAINS)
REMOVE MORE TN & TP FROM SURFACE DISCHARGES
• Add Biosorption Activated Media (BAM)to the discharge of an LID, such as from rain gardens (depression areas), in swale blocks, and the discharge from wet detention ponds.
• Already being used in greenroofs, which specify the use pollution control media.
AVAILABLE BAM ANDCAN ALSO USE OTHERS AS APPROVED
DESCRIPTION OF MEDIA
Media and Typical Location in BMP Treatment Train MATERIAL TSS REMOVAL EFFICIENCY
TN REMOVAL EFFICIENCY
TP REMOVAL** EFFICIENCY
B&G ECT (ref A) Expanded Clay2
A first BMP, ex. Up-Flow Filter in Baff le box and Tire Chips1
a constructed w etland# (USER DEFINED BMP) 70% 55% 65% 96 in/hrB&G OTE (ref A,B) Organics8
Up-flow Filter at Wet Pond or Dry Basin Outflow Tire Chips1
(FILTRATION) Expanded Clay4 60% 45% 45% 96 in/hrB&G ECT3 (ref C) Expanded Clay4
After Wet Detention using Up-flow Filter Tire Chip1 60% 45% 45% 96 in/hr
SAT (ref D) Sand3
A first BMP, as a Dow n-flow Filter (FILTRATION) 85% 30% 45% 2 in/hrB&G CTS (ref E,F) Clay6
Dow n-Flow Filters 12" depth*** at w et pond or dry basin Tire Crumb5
pervious pave, tree w ell, rain garden, sw ale, and strips Sand7 & Topsoil9 90% 60% 90% 1.0 in/hrB&G CTS (ref E,F) Clay6
Dow n-Flow Filters 24" depth*** at w et pond or dry basin Tire Crumb5
pervious pave, tree w ell, rain garden, sw ale, and strips Sand7 & Topsoil9 95% 75% 95% 1.0 in/hr
PROJECTED TREATMENT PERFORMANCE * TYPICAL OPERATING
LIMITING FILTRATION RATE
(in/hr)
COMPUTATIONAL AIDS
• FDEP Harper Report (FDEP, 2007) addressing Florida conditions and average annual conditions, and is site specific, uses look up tables, does not address series and parallel configurations
• Computer Programs• SMADA, stormwater management and design aids.• SWMM , primarily hydraulic and peak flow oriented with additions for pollution control.• State Manuals, like from Virginia, New Hampshire, D.C., Colorado, Texas, etc. • Municipal Manuals, like from Orange, Duval and Pinellas Counties, Nashville, etc.• Proprietary usually regional and for one or a few BMPs separately.• None address BMP placement in series or parallel.• None or very limited calculations for TMDL, some event based.• BMPTRAINS, application of FDEP Harper Report of 2007 with evaluation and
performance data for new BMPs since 2017
RETENTION EFFICIENCY CALCULATIONS• Calculation of runoff in the BMPTRAINS model uses the tabular retention
efficiency relationships developed by Harper and Baker (2007) – App. D
NOTE: There are 80 of these tables.
MODELS THAT CONSIDER LID BMPsHOWEVER AVERAGE ANNUAL REMOVAL (TMDL) NOT ADDRESSED
Stormwater Model / BMPs
Ret
entio
n B
iore
tent
ion
Dry
Dete
ntio
n
Swal
e
Gre
en R
oof
Filte
r Str
ip &
B
uffe
rPe
rmea
ble
Pave
men
t
Sand
Filt
er
Wat
er
Har
vest
ing
Wet
Det
entio
n
Bui
lt W
etla
nd
Rai
n G
arde
n
Exfil
tratio
n
Jordan/Falls Lake Model x x x x x x x x x x
BMP SELECT Model x x x x x x x xClinton River SET x x x x x x x xVirginia Runoff
Reduction x x x x x x
DES Simple Method Pollutant Loading x x x x x x x x x x
Colorado x x x x x x x xD.C. Green x x x x
SMADA x x x xBMPTRAINS x x x x x x x x x x
WHAT WOULD BE NEEDED TO DESIGN EFFECTIVE STORMWATER BMP TREATMENT TRAINS AND QUANTIFY LOAD
REDUCTIONS?• Current “presumptive BMP design criteria” do not achieve high
level of treatment needed for discharges to impaired water bodies – need LID BMPs to expand toolbox
• Must be able to quantify the pre-development stormwater loadings
• Must be able to quantify the post-development stormwater loadings
• Must be able to quantify and demonstrate effectiveness of each BMP, including LID BMPs, in treatment trains
• AND.. Calculate relative costs of various BMP combinations
WHY BMPTRAINS MODEL
• Model developed in cooperation with DEP, WMDs, consultants, and DOT• Model is in the public domain• Model incorporates the latest information relative to designing stormwater
treatment systems in Florida:• Florida annual rainfall by zones and location• Includes local watershed soil and cover conditions• Statewide Event Mean Concentrations• Statewide stormwater BMP effectiveness data • Latest LID BMP effectiveness data• Stormwater LID BMP design criteria (developed for Statewide
Stormwater Rule)
USE OF THE BMPTRAINS MODEL
• Evaluates whether a project is meeting Net Improvement• Evaluates site planning/BMP treatment train options• Evaluates load reduction of BMP treatment train options• Evaluates costs of BMP treatment train options• Used to evaluate ERP/BMP options for projects in Lee
County, Pinellas County• Used to evaluate BMP options for St. Joe Sector Plan in
Bay County • Used to evaluate LID options in ERP aps to DEP & WMDs• Used by FDOT and their consultants
SUMMARY
• The LID BMPs in the Pinellas County LID Manual provide new tools that reduce the volume and pollutant loading of stormwater discharges.
• The five highlighted LID BMPs in the Manual reduce the volume of stormwater discharge thereby reducing stormwater pollutant loadings. Pervious pavements and rain gardens function as storage with infiltration areas. The volume of runoff decreases when the impervious area is reduced or is disconnected
using pervious areas for pre-treatment. Greenroof storage adds to evapotranspiration, thus reduces discharge volume. Swales partly infiltrate, and usually are part of the transport drainage system.
• Efficiencies of LID BMPs and BMP treatment trains vary throughout the State due to variability in rainfall and runoff characteristics. Site specific data is available for Pinellas County.
• Computational aids should simplify and validate the calculations for a project site. BMPTRAINS model satisfies all requirements for a reasonable prediction of performance.
B Y : C L AR K H U L L , E R I C L I V I N G S T O N AN D M AR T Y W AN I E L I S T A
QUESTIONS, REMARKS AND DISCUSSION
2017Pinellas County
Pinellas County Stormwater Management Manual Training
Workshop
Characteristics of Rainfall Events at Selected Meteorological Sites
- Rainfall is highly variable in the number of “small” and “large” events -This impacts both runoff generation as well as treatment system
performance efficiency
Bra
nfor
d
Cro
ss C
ity
Ft.
Mye
rs
Jac
kson
ville
Key
Wes
t
Mel
bour
ne
Mia
mi
Orla
ndo
Pen
saco
la
Tal
laha
ssee
Tam
pa
Perc
ent o
f Ann
ual R
ainf
all E
vent
sLe
ss T
han
1 in
ch (%
)
80
82
84
86
88
90
92
94 B
ranf
ord
Cro
ss C
ity
Ft.
Mye
rs
Jac
kson
ville
Key
Wes
t
Mel
bour
ne
Mia
mi
Orla
ndo
Pen
saco
la
Tal
laha
ssee
Tam
pa
Num
ber o
f Ann
ual R
ainf
all E
vent
s
100
110
120
130
140
150
160
Highest: 158 events in MiamiLowest: 104 events in Cross City
Bran
ford
Cro
ss C
ity
Fort
Mye
rs
Jack
sonv
ille
Key
Wes
t
Mel
bour
ne
Mia
mi
Orla
ndo
Pens
acol
a
Talla
hass
ee
Tam
pa
Mea
n An
tece
dant
Dry
Per
iod
(day
s)
0
1
2
3
4
5
6
Dry Season Wet Season
VARIABILITY IN INTER-EVENT DRY PERIOD
Variability in rainfall inter-event
times impacts:
- Runoff C values
- Recovery and performance efficiency of stormwater management systems, especially dry retention
4.40
2.27
3.96
3.03
4.143.92
3.59
4.87
5.63
3.36
3.73
4.65
1.42
FLORIDA EMC VALUESLand Use CategoryEMC (mg/l)
Total N Total PLow Density Residential1 1.645 0.27
Single Family 2.07 0.327
Multi-Family 2.32 0.520
Low Intensity Commercial 1.13 0.188
High Intensity Commercial 2.40 0.345
Light Industrial 1.20 0.260
Highway 1.52 0.200
Agricultural
Pasture 3.51 0.686
Citrus 2.24 0.183
Row Crops 2.65 0.593
Mining/Extractive 1.18 0.150
Range land/park land 1.15 0.055
Natural vegetative community 1.22 0.213
- Values reflect discharge concentrations without any
pre-treatment
NOTE: In BMPTRAINS, there is an overwriteto the these default concentrations and check with reviewers for overwrite conditions
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
LD R
es.
SF R
es.
MF
Res.
LI C
omm
.
HI C
omm
Indu
stria
l
High
way
Past
ure
Citr
us
Row
Cro
ps
Min
ing
Comparison of Typical Nitrogen Concentrations in Stormwater from Developed Lands
Typical natural
area conc.Tota
l Nitr
ogen
Con
c. (m
g/L)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
LD R
es.
SF R
es.
MF
Res.
LI C
omm
.
HI C
omm
Indu
stria
l
High
way
Past
ure
Citr
us
Row
Cro
ps
Min
ing
Comparison of Typical PhosphorusConcentrations in Stormwater from Developed Lands
Typical natural
area conc.
Tota
l Pho
spho
rus C
onc.
(mg/
L)
Monitored State Parks Used for Natural Area EMCs
Source: ERD, Orlando
SUMMARY OF FLORIDA UPLAND LAND USE CLASSIFICATIONS(SOURCE: FFWCC)
ClassificationArea
(acres)Percent of Total
Coastal Strand 15,008 0.1Dry Prairie 1,227,697 11.4
Hardwood Hammock/Forest 980,612 9.1Mixed Pine/Hardwood Forest 889,010 8.3
Pinelands 6,528,121 60.7Sand Pine Scrub 194,135 1.8
Sandhill 761,359 7.1Tropical Hardwood Hammock 15,390 0.1
Xeric Oak Scrub 146,823 1.4Totals: 10,758,155 100.0
Monitored natural areas include more than 92% of upland land covers in Florida
Land Type N Total N(µg/l)
Total P(µg/l)
Dry Prairie 12 2,025 184Marl Prairie 6 684 12
Mesic Flatwoods 30 1,087 43Ruderal/Upland Pine 5 1,694 162Scrubby Flatwoods 13 1,155 27Upland Hardwood 79 1,042 346
Wet Flatwoods 76 1,213 21Wet Prairie 23 1,095 15Xeric Scrub 3 1,596 156
Natural Land Use Runoff Concentrations
SCS CURVE NUMBER (CN)METHODOLOGY
• Common methodology used in many public and proprietary models, Ref: NRCS TR-55 document titled “Urban Hydrology for Small Watersheds”
• Curve numbers are empirically derived values which predict runoff as a function of soil type and land cover
• Can be used to predict runoff depths and volumes
• Runoff generation based on impervious area, soil types, and land cover
• Model incorporates two basic parameters:• Directly connected impervious area (DCIA)
• Percentage of impervious area with a direct hydraulic connection to the drainage system (0 – 100%)• Curve Number (CN)
• Measure of the runoff generating potential of the pervious areas (grass, landscaping, etc.) and impervious areas which are not DCIA (30 – 100)
HOURLY RAINFALL SITES USED FOR RUNOFF
MODELING
- 45 SITES TOTAL
- RUNOFF MODELING CONDUCTED FOR EACH RAIN
EVENT AT EACH SITE OVER AVAILABLE PERIOD OF
RECORD
Meteorological Sites Included in Runoff Modeling
C VALUES FOR VARIOUS COMBINATIONS OF CN AND DCIA IN PINELLAS COUNTY
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 10030 0.004 0.045 0.086 0.127 0.168 0.209 0.250 0.291 0.332 0.373 0.414 0.455 0.496 0.536 0.577 0.618 0.659 0.700 0.741 0.782 0.82335 0.007 0.048 0.089 0.129 0.170 0.211 0.252 0.293 0.333 0.374 0.415 0.456 0.497 0.537 0.578 0.619 0.660 0.701 0.741 0.782 0.82340 0.011 0.051 0.092 0.133 0.173 0.214 0.254 0.295 0.336 0.376 0.417 0.458 0.498 0.539 0.579 0.620 0.661 0.701 0.742 0.782 0.82345 0.016 0.056 0.096 0.137 0.177 0.217 0.258 0.298 0.339 0.379 0.419 0.460 0.500 0.540 0.581 0.621 0.662 0.702 0.742 0.783 0.82350 0.022 0.062 0.102 0.142 0.182 0.222 0.262 0.302 0.342 0.382 0.423 0.463 0.503 0.543 0.583 0.623 0.663 0.703 0.743 0.783 0.82355 0.030 0.070 0.109 0.149 0.189 0.228 0.268 0.308 0.347 0.387 0.427 0.466 0.506 0.546 0.585 0.625 0.664 0.704 0.744 0.783 0.82360 0.040 0.080 0.119 0.158 0.197 0.236 0.275 0.314 0.353 0.393 0.432 0.471 0.510 0.549 0.588 0.627 0.667 0.706 0.745 0.784 0.82365 0.054 0.092 0.131 0.169 0.208 0.246 0.285 0.323 0.362 0.400 0.438 0.477 0.515 0.554 0.592 0.631 0.669 0.708 0.746 0.785 0.82370 0.071 0.109 0.147 0.184 0.222 0.259 0.297 0.335 0.372 0.410 0.447 0.485 0.522 0.560 0.598 0.635 0.673 0.710 0.748 0.785 0.82375 0.096 0.132 0.168 0.205 0.241 0.277 0.314 0.350 0.387 0.423 0.459 0.496 0.532 0.568 0.605 0.641 0.678 0.714 0.750 0.787 0.82380 0.130 0.165 0.199 0.234 0.268 0.303 0.338 0.372 0.407 0.442 0.476 0.511 0.546 0.580 0.615 0.650 0.684 0.719 0.754 0.788 0.82385 0.182 0.214 0.246 0.278 0.310 0.342 0.374 0.406 0.438 0.470 0.502 0.534 0.566 0.599 0.631 0.663 0.695 0.727 0.759 0.791 0.82390 0.266 0.294 0.322 0.350 0.378 0.406 0.433 0.461 0.489 0.517 0.545 0.573 0.600 0.628 0.656 0.684 0.712 0.740 0.767 0.795 0.82395 0.429 0.449 0.469 0.488 0.508 0.528 0.547 0.567 0.587 0.606 0.626 0.646 0.665 0.685 0.705 0.725 0.744 0.764 0.784 0.803 0.82398 0.616 0.626 0.636 0.647 0.657 0.667 0.678 0.688 0.699 0.709 0.719 0.730 0.740 0.750 0.761 0.771 0.782 0.792 0.802 0.813 0.823
Percent DCIA
Zone 4Mean Annual Runoff Coefficients (C Values) as a Function
of DCIA Percentage and Non-DCIA Curve Number (CN)NDCIA
CN
Pensacola/Tallahassee
Curve Number
30 40 50 60 70 80 90 100
DCIA
0
10
20
30
40
50
60
70
80
90
100
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Runoff Coefficient
Key West
Curve Number
30 40 50 60 70 80 90 100DC
IA0
10
20
30
40
50
60
70
80
90
100
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Runoff Coefficient
Annual C Values as a Function of DCIA and non-DCIA Curve Number