Land Development Characteristics (Module 6) Robert Pitt and Celina - - PowerPoint PPT Presentation

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Land Development Characteristics (Module 6)

Robert Pitt and Celina Bochis

Department of Civil, Construction and Environmental Engineering The University of Alabama Tuscaloosa, AL 35487

Example of 1 m monochromatic aerial photograph (USGS photo) Example of high resolution color satellite image (Google)

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Summary of Measured Areas

• Totally connected impervious areas: 25.9 acres

– parking 15.3 acres – roofs (flat) 8.2 acres – streets (1.2 curb-miles and 33 ft wide) 2.4 acres

• Landscaped/open space 15.4 acres
• Total Area 41.3 acres

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Residential Area Source Areas

1.07 Undeveloped area 0.57 Streets 3.96 1.75 2.21 Subtotals 2.68 1.07 1.61 Landscaped areas 0.10 0.04 0.06 Sidewalks 0.27 0.12 0.15 Driveways 0.91 0.52 0.39 Roofs Total area Small lots Large lots Area (acres) Total area: 5.60 acres

Jefferson Co. MS4 Monitoring Sites Birmingham, AL Little Shades Creek Jefferson Co, AL

Little Shades Creek Subwatersheds

5218 2589 585 951 676 417 Total 1207 621 164 199 153 70 All other 82 42 7 17 8 8 Commercial 109 58 13 38 School/ church 87 27 13 47 Multi-family 122 94 8 20 Town homes 3611 1747 401 676 448 339 Single family Total All

• thers

4 3 2 1 Area (acres)

Field Data Collection

• Delineation of the watersheds and neighborhoods
• Single land use neighborhood surveys: 6 to 12 per study

area land use to determine the variability of the development characteristics

• Site Inventory had 2 parts:

– Field data collection – Aerial photographic measurements of different land covers

• Each site had at least two photographs taken:

– one as a general view – one as a close-up of the street texture

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Field Inventory Sheet Prepared for Each Neighborhood

When in the field we look for:

• 1. Roof types (flat or pitched)
• 2. Roof connections (connected,

disconnected)

• 3. Pavement conditions and

texture (smooth, interm., rough)

• 4. Storm drainage type

(grass swales, curb and gutters, and roof drains)

Village Creek Site (SWMA 002) Birmingham, AL Characteristics of Land Development in Rocky Ridge

100 100 100 100 100 Total 38.67 9.4 76 84.82 89.19 Pervious Areas 1.14 9 6.2 4.7 Impervious areas draining to pervious areas 60.19 90.6 15 8.98 6.11 Directly connected imperviousness Office parks Strip commercial High density Medium density pre 1960 Low density

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Little Shades Creek Watershed

Average Land Cover Distribution

High Density Residential (6 houses/acre)

TIA = 25% DCIA = 15% TR-55 = 52 - 65% TIA = 20% DCIA = 15% TR-55 = 25-52% TIA = 10% DCIA = 6.7% TR-55 = 20-25% TIA = 61% DCIA = 60% TR-55 = 85% TIA = 67% DCIA = 64% TR-55 = 85%

Little Shades Creek Watershed

Variation in Land Cover Distribution

Little Shades Creek and Jefferson Co. Drainage Areas: TIA by Land Use

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Little Shades Creek and Jefferson Co. Drainage Areas: DCIA by Land Use

Average Percent Directly Connected Impervious Area

85 71 COM 72 50 IND 65 23 APARTMENTS 23 5 LDR (< 2 units/ac) 39 11 MDR (2-6 units/ac) 52 21 HDR (> 6 units/ac) TR – 55

(using interpolation)

Local Conditions Land Use

• TR- 55 assumes all impervious areas to be directly connected to the

drainage system

• Overestimation of impervious cover for local conditions

Curb Length vs Land Use

1 mile = 1.6 km 1 ac = 0.4 ha

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Relationship between basin development, riparian buffer width, and biological integrity in Puget Sound lowland streams. (From May, C.W. Assessment of the Cumulative Effects of Urbanization

• n Small Streams in the Puget Sound Lowland Ecoregion:

Implications for Salmonid Resource Management. Ph.D. dissertation, University of Washington, Seattle. 1996.

Poor Fair/Good Good/Excellent Aquatic Life Biodiversity Highly Unstable Unstable Stable Channel Stability Damaged 26–100% Imperviousness Impacted 11– 25% Imperviousness Sensitive 0 – 10% Imperviousness Urban Steam Classification

Figure and Table from Center of Watershed Protection

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1 10 100 Directly Connected Impervious Area (%) Rv Sandy Soil Rv Silty Soil Rv Clayey Soil Rv

Good Fair Poor

Relationship between Directly Connected Impervious Areas, Volumetric Runoff Coefficient, and Expected Biological Conditions

WinSLAMM v 9.2 Output Summary

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Poor 0.29 12 21 67 5120

RES Little Shades Creek

Poor 0.61 3.4 61 36 228

COM ALJC 012

Poor 0.30 7.9 28 64 133

Resid. Med. Dens. ALJC 010

Poor 0.37 12 34 54 102

Resid. High Dens. ALJC 009

Poor 0.51 7.3 53 40 721

IND ALJC 002

Poor 0.67 2.8 72 25 341

IND ALJC 001

Expected Biological Conditions of Receiving Waters Vol. Runoff Coeff. (Rv) Disconnected Impervious Areas (%) Directly Connected Impervious Areas (%) Pervious Areas (%) Area (ac) Major Land Use Watershed ID

Flow-Duration Curves for Different Stormwater Conservation Design Practices

20 40 60 80 100 120 140 0.1 1 10 100

% Greater than Discharge Rate Discharge (cfs) Top Set: No Controls Swales Bottom Set: Biorentention Swales and Bioretention Pond and Bioretention Pond, Swales and Bioretention

Flow Duration Curves are Ranked in Order of Peak Flows

Middle Set: Pond Pond and Swales

Cost Effectiveness of Stormwater Control Practices for Runoff Volume Reductions

Swales and Bioretention Pond and Bioretention Bioretention Pond, Swales and Bioretention Pond Pond and Swale Swale

10 20 30 40 50 60 70 80 20 40 60 80

Max % Runoff Reduced $/1000 cu. Ft Reduced

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Example of Stormwater Control Implementation

fair poor poor poor poor

Expected biological conditions in receiving waters (based on Rv)

0.03 0.03 0.03 0.07 n/a

Unit Removal Costs for Runoff Volume ($/ft3)

67% 58% 10% 1.4% n/a

% Reduction of Total Runoff Volume Discharges

0.20 0.26 0.54 0.60 0.61

Runoff Coefficient (Rv)

2456 1974 404 118

Annualized Total Costs ($/year/ac) Pond, Swales and Bioretention Bioretention Only Swales Only Pond Only No controls

• Site ALJC 012
• Area 228 acres = 92.3 ha
• Bioretention devices give the greatest reduction in runoff volume discharged
• The biological conditions improved from “poor” to “fair” due to stormwater controls
• These graphs illustrate the relationships between

the directly connected impervious area percentages and the calculated volumetric runoff coefficients (Rv) for each land use category (using the average land use characteristics), based on 43 years of local rain data.

• Rv is relatively constant until the 10 to 15% directly

connected impervious cover values are reached (at Rv values of about 0.07 for sandy soil areas and 0.16 for clayey soil areas), the point where receiving water degradation typically is observed to start.

• The 25 to 30% directly connected impervious levels

(where significant degradation is observed), is associated with Rv values of about 0.14 for sandy soil areas and 0.25 for clayey soil areas, and is where the curves start to greatly increase in slope.