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

Land Development Characteristics (Module 6) Robert Pitt and Celina Bochis Department of Civil, Construction and Environmental Engineering The University of Alabama Example of 1 m monochromatic aerial photograph (USGS photo) Tuscaloosa, AL 35487 Example of high resolution color satellite image (Google) 1

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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 4

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Residential Area Source Areas Area (acres) Large Small Total lots lots area Roofs 0.39 0.52 0.91 Driveways 0.15 0.12 0.27 Sidewalks 0.06 0.04 0.10 Landscaped 1.61 1.07 2.68 areas Subtotals 2.21 1.75 3.96 Little Shades Creek Streets 0.57 Jefferson Co, AL Undeveloped 1.07 area Jefferson Co. MS4 Monitoring Sites Total area: 5.60 acres Birmingham, AL Little Shades Creek Subwatersheds Field Data Collection Area (acres) 1 2 3 4 All Total • Delineation of the watersheds and neighborhoods others Single 339 448 676 401 1747 3611 • Single land use neighborhood surveys: 6 to 12 per study family area land use to determine the variability of the Town 0 20 8 0 94 122 development characteristics homes Multi-family 0 47 13 0 27 87 • Site Inventory had 2 parts: – Field data collection School/ 0 0 38 13 58 109 church – Aerial photographic measurements of different land covers Commercial 8 8 17 7 42 82 All other 70 153 199 164 621 1207 • Each site had at least two photographs taken: – one as a general view Total 417 676 951 585 2589 5218 – one as a close-up of the street texture 6

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 Low Medium High Strip Office density density pre density commercial parks 1960 Directly 6.11 8.98 15 90.6 60.19 connected imperviousness Impervious 4.7 6.2 9 0 1.14 areas draining to pervious areas Pervious Areas 89.19 84.82 76 9.4 38.67 Total 100 100 100 100 100 7

Little Shades Creek Watershed Average Land Cover Distribution TIA = 61% TIA = 20% DCIA = 60% High Density Residential (6 houses/acre) DCIA = 15% TR-55 = 85% TR-55 = 25-52% TIA = 67% TIA = 10% DCIA = 64% DCIA = 6.7% TR-55 = 85% TR-55 = 20-25% TIA = 25% DCIA = 15% TR-55 = 52 - 65% Little Shades Creek Watershed Little Shades Creek and Jefferson Co. Variation in Land Cover Distribution Drainage Areas: TIA by Land Use 8

Average Percent Directly Connected Little Shades Creek and Jefferson Co. Impervious Area Drainage Areas: DCIA by Land Use Local TR – 55 Land Use Conditions (using interpolation) HDR (> 6 units/ac) 21 52 MDR (2-6 units/ac) 11 39 LDR (< 2 units/ac) 5 23 APARTMENTS 23 65 COM 71 85 IND 50 72 • 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 9

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Figure and Table from Center of Watershed Protection Urban Steam Sensitive Impacted Damaged Classification 0 – 10% 11– 25% 26–100% Imperviousness Imperviousness Imperviousness Relationship between basin development, riparian buffer width, Channel Stable Unstable Highly Unstable and biological integrity in Puget Sound lowland streams. (From Stability May, C.W. Assessment of the Cumulative Effects of Urbanization Aquatic Life Good/Excellent Fair/Good Poor Biodiversity on Small Streams in the Puget Sound Lowland Ecoregion: Implications for Salmonid Resource Management. Ph.D. dissertation, University of Washington, Seattle. 1996. Relationship between Directly Connected WinSLAMM v 9.2 Output Summary Impervious Areas, Volumetric Runoff Coefficient, and Expected Biological Conditions 1 0.9 0.8 Poor 0.7 0.6 Fair Good Rv 0.5 0.4 0.3 0.2 0.1 0 1 10 100 Directly Connected Impervious Area (%) Sandy Soil Rv Silty Soil Rv Clayey Soil Rv 11

Expected Directly Vol. Major Area Pervious Disconnected Biological Watershed Connected Runoff Land (ac ) Areas Impervious Conditions of Coeff. ID Impervious Receiving Use (%) Areas (%) (Rv) Areas (%) Waters ALJC 341 25 72 2.8 0.67 Poor IND 001 ALJC IND 721 40 53 7.3 0.51 Poor 002 Resid. ALJC High 102 54 34 12 0.37 Poor 009 Dens. Resid. ALJC 133 64 28 7.9 0.30 Poor Med. 010 Dens. ALJC 228 36 61 3.4 0.61 Poor COM 012 Little 5120 67 21 12 0.29 Poor Shades RES Creek Flow-Duration Curves for Different Cost Effectiveness of Stormwater Control Stormwater Conservation Design Practices Practices for Runoff Volume Reductions 140 Flow Duration Curves are Ranked in Order of Peak Flows 80 120 70 Pond Top Set: No Controls Swales 100 60 $/1000 cu. Ft Reduced Discharge (cfs) 50 80 Pond and Swale 40 Middle Set: Pond, Swales 60 Pond Pond and and Bioretention Pond and Swales Swale Bioretention 30 Swales and 40 Bioretention Bioretention 20 Bottom Set: Biorentention 20 Swales and Bioretention 10 Pond and Bioretention Pond, Swales and Bioretention 0 0 0.1 1 10 100 0 20 40 60 80 % Greater than Discharge Rate Max % Runoff Reduced 12

Example of Stormwater Control Implementation • These graphs illustrate the relationships between the directly connected impervious area Pond, percentages and the calculated volumetric runoff No Pond Swales Bioretention Swales and controls Only Only Only coefficients (Rv) for each land use category (using Bioretention Annualized Total Costs the average land use characteristics), based on 43 0 118 404 1974 2456 ($/year/ac) years of local rain data. Runoff Coefficient (Rv) 0.61 0.60 0.54 0.26 0.20 • Rv is relatively constant until the 10 to 15% directly % Reduction of Total Runoff n/a 1.4% 10% 58% 67% Volume Discharges connected impervious cover values are reached (at Unit Removal Costs for Rv values of about 0.07 for sandy soil areas and 0.16 n/a 0.07 0.03 0.03 0.03 Runoff Volume ($/ft 3 ) for clayey soil areas), the point where receiving Expected biological water degradation typically is observed to start. conditions in receiving waters poor poor poor poor fair (based on Rv) • The 25 to 30% directly connected impervious levels • Site ALJC 012 (where significant degradation is observed), is • Area 228 acres = 92.3 ha associated with Rv values of about 0.14 for sandy soil • Bioretention devices give the greatest reduction in runoff volume discharged areas and 0.25 for clayey soil areas, and is where the • The biological conditions improved from “poor” to “fair” due to stormwater controls curves start to greatly increase in slope. 13