Thesis (Ed.D.) -- Teachers College, Columbia University, 1991. / Typescript; issued also on microfilm. Sponsor: John P. Allegrante. Dissertation Committee: Bernard Gutin. Includes bibliographical references (leaves 171-185).

Bioretention cells (also known as rain gardens) are a Low Impact Development (LID) method for sustainable stormwater management. An increasingly popular form of urban stormwater infrastructure, bioretention cells use an engineered, vegetated-soil-system to both reduce quantity and enhance quality of stormwater. The ability of bioretention systems to remove common pollutants from urban stormwater runoff, and reduce runoff volume through evapotranspiration, in a temperature climate during plant senescence were assessed in this full scale field-based study. Stormwater run-off simulations were conducted for 5-, 10-, and 25-year return period storm events at a field site in Victoria, British Columbia, Canada. Tests were run on both, a vegetated cell planted with a mix of Betula nigra, Betula nana, and Salix lutea, and a control cell with turfgrass. Influent and effluent field parameters were recorded for pH and dissolved oxygen (DO), in addition to lab analyses conducted to quantify COD, TN, TON, TP, ortho-phosphate, and TSS removal from the stormwater. Water quality and hydrologic performance were results were compared between the vegetated and control cell using a Wilcoxon Signed Rank Test. In addition, hydrologic results were correlated with daily Evapotranspiration (ET) and meteorological station data using Spearman’s Rho Correlation. The vegetated cells were more effective (p value < 0.05) at retention of water volume, DO, COD, and orthophosphate, when compared to the control. Strong correlations (p value < 0.05) were found between the retention of water volume, and each of ET, maximum temperature, average temperature, minimum temperature, and average wind, for only the vegetated cells. / Graduate

Virginia's new stormwater regulations involve the use of the Runoff Reduction Method (RRM), which requires the product of the peak flow rate and runoff volume (Q*RV) from the one-year storm event in the post-development condition to be reduced to eighty percent of the pre-development Q*RV to protect against channel erosion. This study models different bioretention cell sizes in a developed watershed in Blacksburg, Virginia to determine the "performance" at both the sub-watershed and watershed levels. In addition, models of "optimal" bioretention cells sized to meet the RRM for each sub-watershed are evaluated. A direct relationship is determined between the size of the cell required to meet the RRM and the sub-watershed's Natural Resources Conservation Service (NRCS) curve number. However, the required size for some of the cells is much larger than those typically seen. With the RRM applied for all of the sub-watersheds, the resulting hydrograph at the watershed outlet has a lower peak than the pre-development condition. / Master of Science

Despite the runoff reduction efficiencies recommended by various regulatory agencies, minimal research exists regarding the ability of vegetated swales to simultaneously convey and reduce runoff. This study assessed the effect water quality swales distributed among upstream sub-watersheds had on watershed hydrology. The study was also posed to determine how certain design parameters can be dimensioned to increase runoff reduction according to the following modeling scenarios: base, base check dam height, minimum check dam height, maximum check dam height, minimum infiltration rate, maximum infiltration rate, minimum Manning's n, maximum Manning's n, minimum longitudinal slope, and maximum longitudinal slope. Peak flow rate, volume, and time to peak for each scenario were compared to the watershed's existing and predevelopment conditions. With respect to the existing condition, peak flow rate and volume decreased for all scenarios, and the time to peak decreased for most scenarios; the counterintuitive nature of this result was attributed to software error. Overall, the sensitivity analysis produced results contrary to the hypotheses in most cases. The cause of this result can likely be attributed to the vegetated swale design and modeling approaches producing an over designed, under constrained, and/or over discretized stormwater management practice. / Master of Science

This study uses the Natural Resources Conservation Service (NRCS) TR-55 method to quantify the increase in stormwater runoff volume from infill residential redevelopment, or mansionization, in a 34-acre residential subwatershed of Fairfax County, Virginia. Analysis of 10 redeveloped lots in the subwatershed showed an average increase in impervious cover from 8% to 28% after redevelopment, resulting in an average increase in runoff volume of 18% for the 10-year, 24-hour storm. From 1997 to 2009, the total impervious cover in the subwatershed increased from 18% to 25%, resulting in a calculated 6% increase in runoff volume. Low Impact Development (LID) techniques were modeled as retrofits in the subwatershed to mitigate the increase in runoff volume. Measures modeled include bioretention basins, infiltration trenches, amended soils, permeable pavement, and cisterns. Results indicate that placing bioretention basins or infiltration trenches on 0.5% of the subwatershed or amending 20% of the open space with soil composts would reduce the runoff volume back to the 1997 quantity for the 1-year, 24-hour storm. / Master of Science

While many studies have evaluated the hydrologic effects of bioretention at the site level, few have investigated the role bioretention plays when distributed throughout a watershed. This study aims to assess bioretention's effects on an urbanized watershed using two modeled scenarios: one where runoff from many land uses was routed through the practice, and another in which only runoff from large impervious areas was routed. Peak flows, volumes, and lag times from these models were compared to the watershed's current and predeveloped conditions. Both scenarios provided reductions in peak flows with respect to existing conditions for modeled storm events, sometimes to levels below the predeveloped condition. Neither case was able to reduce volumes to predevelopment levels; the option to treat impervious areas had a negligible effect on runoff volume. Both cases were able to extend lag times from the existing development condition. Based on these results, bioretention appears to have the capability to improve watershed hydrologic characteristics. Furthermore, only treating impervious areas could be a viable alternative when funds or space are limiting factors. / Master of Science

This thesis contains two studies that explore different methods of visitor management in recreation. The management strategies studied here are both relatively indirect approaches intended to minimize the environmental and social impacts that visitors cause in protected areas. The Annapolis Rocks study focuses on visitors' evaluations of a site management strategy that shifted camping from a flat, open area to constructed side-hill campsites. A visitor questionnaire was administered before and after the treatment to determine visitors' ratings of importance and satisfaction for various campsite attributes. We found some evidence of visitor displacement but concluded that the site management strategy supported the intentions of the managers. The Leave No Trace study evaluates the effectiveness of the Trainer courses in improving the knowledge, ethics, and behavior of the participants and encouraging them to teach others in the community. This study employed pre-course, post-course, and follow-up questionnaires to evaluate the participants' short-term and long-term gains from the course. Trainer course participants showed significant short-term and long-term gains from the course, with a slight decline in the total gain four months after the course. The participants showed improvements in low-impact behaviors, suggesting that education is an effective visitor management strategy. These studies demonstrate that managers can be successful at controlling visitor impacts without relying on stringent regulations and enforcement. / Master of Science

This paper serves as a “kicking-the-tires” analysis of low impact developments as a method of stormwater management. Specifically, this paper examines the feasibility, benefit, and current practice of low impact developments in Austin, Texas. Merits, strengths, and weakness are comparatively determined primarily on the basis of the impact and efficiency of design, particularly relating to ability to handle water volume and potential to improve water quality. By examining case studies and “applied” examples the potential of low impact development application is considered for the expected, potential, and/or alleged benefits of low impact implementation. / text

Low impact development (LID), the practice of preserving and restoring natural water cycles in urban development, is considered the next step in stormwater management. Policy and governance play a strong role in the adoption of LID. There has been progress in implementing LID in the Greater Toronto Area but less progress in Southern Ontario in general. This research identifies barriers and opportunities to implementing LID in the context of policy and governance in Southern Ontario. The barriers, opportunities, and policy are identified using a focused literature review, then verified and further explored through key informant interviews. Data are synthesised to produce an Enhanced Governance Model (EGM) for implementing LID. The EGM is evaluated by key informants and further refined. Findings show that public education and provincial-level standards are fundamental to widespread adoption of LID. Five opportunities for jurisdictional integration in stormwater governance are identified and their implications discussed.

Groundwater dependent ecosystems (GDEs), including wetlands and river baseflow systems, are a topic of substantial scientific study. The degradation of GDEs due to urbanization has been well documented. An altered hydrologic regime, through increased impervious area resulting in a flashier hydrologic regime with lower troughs, higher peaks, and quicker changes, has been recognized as a main factor affecting ecological condition. Yet studies on GDEs rarely include a hydrologic modelling component. In this study, the conjunctive hydrologic model MIKE SHE was used to simulate the Lovers Creek subwatershed near Barrie, ON. The hydrologic regime was simulated for pre-development (natural), current (urbanized), and various low-impact development (LID) land use scenarios. The results were linked to the ecological condition via the TQmean metric, which has been used in the literature to relate the hydrologic and ecological conditions of streams. The highest percentage LID scenario restored, on average, 11% of the reduction in TQmean that occurred from pre-development to urbanized conditions, indicating that LID has the potential to protect GDEs in urbanized watersheds. It is expected that the effect of LID would be amplified if considered on a more local scale within a predominantly high density urban area. Recommendations for future modelling efforts to evaluate GDEs and represent LID are made.