1 Relationships Between Land Cover and Infiltration Rates in Urban Landscapes Bita Alizadehtazi, Kimberly DiGiovanni, Patrick L. Gurian, Franco Montalto Department of Civil, Architectural and Environmental Engineering, The Sustainable Water Resource Engineering oratory (SWRE ) Drexel University, Philadelphia, PA 19104 September 27, 2011
Outline 2 Introduction Research Objectives and Hypotheses Methods Experimental Analytical Results Conclusions ekisticsdesignstudio.com
Introduction Conventional Urban Green Spaces 3 Vegetated Courtyard Courtesy of USDA NRCS Backyard Urban Park
Conventional Urban Green Spaces (Cont.) 4 Tree Pits Courtesy of Tatiana Morin Courtesy of Tatiana Morin
Green Infrastructure Sites 5 Porous Pavers Porous Rubberized Safety Materials Porous Standard Porous Asphalt Concrete Courtesy of USDA NRCS
Green Infrastructure Sites (Cont.) 6 Bioretention
Research Goals 7 Determine whether different urban surfaces have statistically different infiltration rates Hypothesis1: Differences are significant Ascertain whether specific characteristics (bulk density, antecedent dry period, initial moisture content) significantly alter infiltration rates Hypothesis2: These parameters are less significant in determining infiltration rate than surface treatment
Experimental Methods 8 Perform infiltration testing on a diverse across section of urban green spaces Simulated rainfall rate (r, cm/min) r = [H1 H2] / T f H1 Runoff rate (rot, cm/min) ro t = V t / (457.30*t) H2 Infiltration rate (it, cm /min) i t = r ro t Van Es, H.M. and R.R. Schindelbeck (undated). Field Procedures and Data Analysis for the Cornell Sprinkle Rainfall Simulator. Instructions For Use and Instructions for Replacing Infiltrometer Tubes from the Cornell Precision Agriculture Website, http://www.css.cornell.edu/research/precisionag/infiltrometer.htm. Kean Goh, CDPR
Sites with Number of Tests 9 Sites Number of Tests Bioretention Facilities 50 Tree Pits (w/o guards) 20 Tree Pits (w/ guards) 18 Urban Parks 5 Backyards 4 Porous Asphalts 16 Porous Concrete 5 Porous Rubberized Safety Mat. 11 Porous Pavers 5 Vegetated Courtyards 5 Google Map
Analytical Methods Test whether range of measured values at each treatment type are normally distributed Q Q Plot Assess the significance of the differences between treatments Kruskal Wallis test Perform a sensitivity analysis (Spearman R) Bulk Density Antecedent Dry Period Initial Moisture Content 10
Methodology for Selecting Infiltration Rates from Experimental Data 11 Infiltration Data Bioretention Facility Location 1 Infiltration Rate Porous Asphalt Location 1 Infiltration Rate (cm/min) 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.00 0 10 20 30 40 50 60 70 Time (min) Infiltration Rate (cm/min) 0.60 0.50 0.40 0.30 0.20 0.10 0.00 0.10 0 5 10 15 20 Time (min)
Methodology for Selecting Infiltration Rates from Experimental Data 12 Infiltration Data Bioretention Facility Location 1 Infiltration Rate Porous Asphalt Location 1 Infiltration Rate (cm/min) 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.00 0 10 20 30 40 50 60 70 Time (min) Steady state value Infiltration Rate (cm/min) 0.60 0.50 0.40 0.30 0.20 0.10 0.00 0.10 Mean value 0 5 10 15 20 Time (min)
Results 13 Infiltration Data
Data Distribution (Q Q plots) 14 Bioretention Facilities Urban Parks Tree Pits (without guards) Tree Pits (with guards)
Data Distribution (Q Q plots) 15 Porous Rubberized Safety Material Porous Asphalt Porous Concrete Porous Pavers
Results 16 Nonparametric Kruskal Wallis Analysis Result: The distribution of infiltration are not the same across various of urban green spaces (H(9) = 48.503, p < 0.01) Reject the null hypothesis Mean Rank Porous Concrete Porous Rubberized Safety Materials Tree Pits (with guards) Backyards Vegetated Courtyards Bioretention Facilities Porous Pavers Porous Asphalts Tree Pits (without guards) Urban Parks 0 20 40 60 80 100 120 140 160
95% Confidence Interval for the Median Infiltration Rates 17 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0
Groups Based on 95% Confidence Interval of Median Infiltration Rates 18 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 High Unclear Middle Low
Sensitivity Analysis Correlation (Spearman R) 19 Initial Soil Moisture Content Bulk Density Antecedent Dry Hours r 0.189 0.200 0.060 Spearman's rho Sig. 0.209 0.183 0.489 r > 0.8 strong correlation r = 0.5 0.8 moderate correlation r < 0.5 weak correlation
Sensitivity Analysis (Scatter plots) 20
Conclusions 21 There is a statistically significant difference between the different treatments (Kruskal Wallis, p < 0.01) with the lowest mean rank of 32.6 for Urban Parks, and the highest mean rank of 135.6 for Porous Concrete Urban Parks, and Tree Pits (w/o guards) have the lowest infiltration performance. Vegetated Courtyards, Tree Pits (w/ guards), Porous Pavers, Backyards, Bioretention Facilities have the middle infiltration performance and Porous Concrete has the highest infiltration performance Porous concrete has the highest average infiltration rates and median performance and Urban Parks has the lowest Tree Pits without guards have the lower average infiltration rate than Tree Pits with guards Porous Rubberized Safety Material has the highest variability of any treatments There is no significant relationship between Bulk density, Initial Soil Moisture Content, Antecedent Dry Hours and Infiltration Rates.
Acknowledgment 22 Nandan Shetty Tatiana Morin Zachary Benedetto Evan Mason
23 Thank You