The stormwater retention pond is a best management practice used for the improvement of runoff water quality before it discharges into larger surface waterbodies. A vortex-type retention pond, called the Nautilus PondTM, is a new design approach for stormwater retention ponds that is expected to produce an internal flow pattern in the pond that is more conducive to removal of sediments from runoff. Since many existing stormwater retention ponds were originally designed only for flood control, most of the ponds are subject to large dead zones, severe short-circuiting and short retention times, which can limit sediment retention in the ponds. In this study, the robustness of the design of the Nautilus PondTM was evaluated by assessing its residence time distribution (RTD) characteristics, flow pattern and sediment deposition patterns under various conditions of flow in the pond. The study was carried out in two physical scale models of a simplified Nautilus PondTM: one with a scale ratio of 1:30.775 for an aspect ratio of 100:2, and the other with a scale ratio of 1:13.289 for a pond of 50:2 aspect ratio. The aspect ratio is the ratio of the pond diameter at its water surface (top width) to the depth of flow, 2 m at corresponding design flow rates, in the pond. First, the RTD characteristics and flow patterns in the ponds were investigated using tracer mass recovery and flow visualization tests allowing different times for steady flow development (flow development time) for the design flows corresponding to 4 m3/s in the 100:2 prototype pond and 1 m3/s in the 50:2 pond. Then, tracer tests were carried out at different flow rates to investigate its effects on the RTD characteristics in both model ponds. The deposition patterns of approximately 50 micron sediment particles (prototype size) were also observed. The best position of a berm around the pond outlet was determined for the 100:2 pond by comparing the RTD characteristics and the sediment deposition patterns in the pond for three different positions of the berm. The residence time distribution characteristics and the sediment deposition pattern were also assessed for the 50:2 pond with a berm placed in a position equivalent to the best position identified in the 100:2 pond tests. It was found that the RTD curves at design flow rates of 4 m3/s and 1 m3/s for different flow development times were very similar to each other for both pond aspect ratios; the flow development time was found to have little effect on the flow characteristics of the ponds. The average baffle factors, short-circuiting indices and Morril dispersion indices were 0.41, 0.20 and 4.1, respectively, for the 100:2 pond aspect ratio, whereas these were 0.23, 0.05 and 8.6 for the 50:2 pond. The flow rate was found to have a significant effect on the RTD characteristics of both ponds. There were multiple peaks in the RTD curves for the lower flow rates tested for the 100:2 pond. This was thought to be a result of the low inflow momentum and high aspect ratio of the pond. As the flow rate was increased, the residence time distribution curve had a single, lower peak. In both ponds, an increase of flow rate caused the baffle factor and short-circuiting index to decrease and the Morril dispersion index to increase indicating that the inflow spent a shorter time in the pond. The sediment deposition pattern tests in both ponds without the berm around the outlet showed that a higher quantity of sediments deposited in the outer peripheral region of 100:2 pond. The 50:2 pond deposited a small amount of sediment along the periphery due to the high velocity inflow jet and lower aspect ratio of the pond. The best position of the berm among those tested was found to be at the 60% of pond bed radius from the center. Though the RTD characteristics for the 100:2 pond with different berm positions were very similar to each other, the 100:2 pond with the berm position at 60% of pond bed radius deposited most of the sediments outside the berm. The RTD characteristics in both ponds showed significant improvement with a berm at the 60% of radius position compared to the ponds without a berm. This improvement was more significant for the 50:2 pond than for the 100:2 pond. Further, the sediment deposition pattern in 100:2 pond with berm at 60% of bed radius showed that the larger sized sediment particles mainly deposited outside the berm and the finer particles deposited inside the berm. The 50:2 pond did not show any significant difference in particle size distribution of the sediments deposited inside and outside of the berm.

The aim of this thesis is to examine and develop new techniques in stormwater Best Management Practices (BMP) for nutrient and erosion reduction and monitoring by incorporation of low impact green technologies and sensor networks. Previous research has found excessive nutrient loading of nitrogen and phosphorus species from urban stormwater runoff can lead to ecological degradation and eutrophication of receiving lakes and rivers (Fareed and Abid, 2005). In response, the Florida Department of Environmental Protection (FDEP) has set forth reduction goals as established in Total Maximum Daily Load (TMDL) reports to reduce nutrient loading and restore, or maintain, Florida water bodies to reasonable conditions. Often times current stormwater management practices are not sufficient to attain these goals and further improvements in system design are required. In order to reach these goals, affordable technologies designed for both nutrient reduction and monitoring of system performance to deepen and improve our understanding of stormwater processes are required. Firstly this thesis examines the performance of three types of continuous-cycle Media Bed Reactors (MBRs) using Bio-activated Adsorptive Media (BAM) for nutrient reduction in three retention ponds located throughout the Central Florida region. Chapter 2 examines the use of a Sloped and Horizontal MBRs arranged in a baffling configuration, whereas Chapter 3 examines the field performance of a Floating MBR arranged in an upflow configuration. Each MBR was analyzed for performance in reducing total phosphorus, soluble reactive phosphorus, total nitrogen, organic nitrogen, ammonia, nitrates + nitrites, turbidity and chlorophyll a species as measured from the influent to effluent ends of the MBR. The results of the experiments indicate that MBRs may be combined with retention ponds to provide "green technology" alternatives for inter-event treatment of nutrient species in urban stormwater runoff by use of recyclable sorption media and solar powered submersible pumps. Secondly the thesis focusses on three new devices for BMP monitoring which may be integrated into wireless networks, including a Groundwater Variable Probe (GVP) for velocity, hydraulic conductivity and dispersion measurements in a retention pond bank (Chapter 4), an affordable Wireless Automated Sampling Network (WASN) for sampling and analysis of nutrient flux gradients in retention ponds (Chapter 5), and finally an Arc-Type Automated Pulse Tracer Velocimeter (APTV) for low velocity and direction surface water measurements in retention ponds and constructed wetlands (Chapter 6). The GVP was integrated with other environmental sensing probes to create a remote sensing station, capable of real-time data analysis of sub-surface conditions including soil moisture, water table stage. Such abilities, when synced with user control capabilities, may help to increase methods of monitoring for applications including erosion control, bank stability predictions, monitoring of groundwater pollutant plume migration, and establishing hydraulic residence times through subsurface BMPs such as permeable reactive barriers. Advancement of this technology may be used by establishing additional sub-stations, thereby creating sensing networks covering broader areas on the kilometer scale. Two methods for velocity calculation were developed for the GVP for low flow (Pe < 0.2) and high flow (Pe > 0.6) conditions. The GVP was found to operate from a 26-505 cmd-1 range in the laboratory to within ±26% of expected velocities for high-flow conditions and effectively measure directional flow angles to within ±14° of expected. Hydraulic conductivity measurements made by the GVP were confirmed to within ±12% as compared to laboratory measurements. The GVP was found capable of measuring the dispersion coefficient in the laboratory, however turbulent interferences caused during injection was found to occur. Further advancement of the technology may be merited to improve dispersion coefficient measurements. Automated water sampling can provide valuable information of the spatial and temporal distribution of pollutant loading in surface water environments. This ability is expanded with the development of the WASN, providing an affordable, ease-of-use method compared to conventional automated water samplers currently on the market. The WASN was found to effectively operate by text activation via GSM cellular networks to an activation module. Propagation of the signal was distributed to collection units via XBee modules operating on point-to-point star communication using an IEEE 802.15.4 protocol. Signal communications effectively transmitted in the field during a storm event to within a range of 200 feet and collected 50 ±4 ml samples at synced timed increments. A tracer study confirmed that no mixing of samples occurs when a factor of safety of 2 is applied to flush times. This technology provides similar abilities to current market devices at down to 10% of the cost, thereby allowing much more sampling locations for a similar budget. The Arc-Type APTV is useful in establishing both low range horizontal velocity fields and expanding low range velocity measurements below detection ranges of mechanical velocity meters. Installation of a field station showed system functionality, which may be integrated with other environmental sensing probes for surface water testing. This may assist in nutrient distribution analysis and understanding the complex behavior of hydraulic retention times within wetland systems. The device was found to work effectively in both lab and field environments from a 0.02 – 5.0 cms-1 range and measure velocity within approximately ±10% of an acoustic Doppler velocimeter and within an average of ±10° of directional measurements. A drop in accuracy was measured for velocity ranges > 4.5 cms-1. The field station operated on 3G CDMA cellular network two-way communication by installation of a Raven cellular modem. Use of LoggerNet software allowed control and data acquisition from anywhere with an internet connection. This thesis also introduces brief discussions on expanding these "point" measurement technologies into sensing networks. Installation of sub-stations with communication protocols to one central master node station may broaden the sensing system into much larger kilometer-scale ranges, thus allowing large spatial analysis of environmental conditions. Such an integration into controllable sensing networks may help bridge the gap and add calibration and verification abilities between fine-resolution "point" measurements and large scale technologies such as Electrical Resistivity Tomography and satellite remote sensing. Furthermore, application of sensing networks may assist in calibration and verification of surface and groundwater models such as ModFlow, SVFlux and FEHM.