Stormwater runoff from urban and urbanizing areas poses a serious threat to water quality, and unless managed properly will impede efforts to restore the Chesapeake Bay.Water quantity, as well as quality, must be considered, and Low Impact Development(LID) is an innovative stormwater management approach that addresses both. LID seeks to mimic a site's predevelopment hydrologic regime by retaining and treating stormwater at the lot level using small, cost-effective landscape features.The purpose for this study was to identify and rank impediments to the implementation of LID in the Virginia portion of the Chesapeake Bay watershed. This was accomplished by going to LID workshops and distributing a survey to stakeholders in attendance. The survey asked respondents to rank the following impediments to the implementation of LID: site-specific & non-structural, property owner acceptance, pollutant removal benefit, development rules, lack of education, maintenance considerations, flooding problems, and cost. Lack of education was ranked as the most important impediment, with development rules following close behind. Pollutant removal benefit was ranked the least important impediment. A second purpose was to assess whether there is a relationship between a county's growth rate and adoption of Better Site Design principles (BSD) and LID. A Code and Ordinance Worksheet was used to evaluate the development rules of 13 counties (6 high growth, 3 medium growth and 4 low growth) within Virginia's portion of the Chesapeake Bay Watershed. The scores from the worksheets were used to determine if the amount of growth pressure experienced by a county influenced the degree to which they incorporated BSD and LID in their local development codes. Statistical testing revealed that the relationship between growth pressure and score on the Code and Ordinance Worksheet was moderate, at best.

Gävle kommun har planer på att exploatera Gävle stad söderut. Planerna finns enligt översiktsplanen Gävle Stad 2025 för bland annat områdena Järvsta och Ersbo. Dessa områden avvattnas mot Järvstabäcken. Detta examensarbete är en utredning av Järvstabäckens avrinningsområde med hänsyn till avrinningsområdets beskaffenhet, klimatförändringar och planerad exploatering. Utifrån dessa faktorer analyseras riskpunkter för översvämning inom avrinningsområdet. Utredningen av avrinningsområdet har genomförts via fältbesök, litteraturstudier och modellering i MIKE FLOOD.   Problematiken kring avrinningsområdet ligger i att Järvstabäcken redan är högt belastad. Med utökade exploateringsområden för bostäder och handelsområden i Hemlingby och Järvsta förväntas Järvstabäcken belastas ytterligare. Ersbo industriområde förväntas även påverka dagvattenflödena då mer andel hårdgjorda ytor tas i anspråk vid utökat handelsområde i kombination med planerad snötipp på industriområdet. Snötippen förväntas påverka flödet under smältperioden.   Riskpunkter för översvämningar återfinns i lågpunkter och passager under E4, Södra Kungsvägen, Upplandsleden och Bomhusvägen. I dessa punkter bör fördröjning av dagvattnet anläggas för att öka kontrollen över flödena och minska risken och kostnaderna för återställande av byggnader och infrastruktur vid översvämning. Riskpunkter i anslutning till befintlig bebyggelse och planerade bostadsområden bör prioriteras för utredning. / Gävle municipality's plans to exploit the city to the south are under the general plan for the areas Järvsta and Ersbo, these areas are dewatered to Järvsta stream. This thesis is an investigation of the Järvsta stream regarding flood risk areas within the basin with consideration to the planned development areas. Investigation of the catchment area has been carried out through field visits, literature studies and modeling with MIKE FLOOD. The problem with Järvsta stream is that it is already heavily loaded. With increased development areas for housing and commercial areas in Hemlingby and Järvsta expected Järvsta stream to be even more loaded in case of extreme rainfall. Ersbo industrial area is also expected to affect surface water flows, hence higher proportion paved surface in combination with the planned landfill for snow in the industrial area expect to impact the flow frequencies. The landfill for snow in Ersbo affects the flow frequencies during the melt period. Risk Points of flooding is found in low points and passages under E4, Södra Kungsvägen, Upplandsleden and Bomhusvägen. These points should delay stormwater to increase control over flows and reduce the risk of flooding and cost of restoration of the buildings and infrastructure. Risk points adjacent to the existing residential areas and planned residential areas should be prioritized for investigation.

Syfte: Fokus på dagvattenhantering är viktigt eftersom översvämnings- och föroreningsrisker blir allt mer förekommande på grund av klimatförändringar och urbanisering med en ökad andel hårdgjorda ytor. Vid exploatering vill kommuner utnyttja befintliga diken istället för att bygga nya ledningssystem, därmed kan de behöva samverka med markavvattningsföretag. Syftet med studien är att underlätta samarbetet mellan markavvattningsföretag och kommuner för att undvika översvämningar och föroreningar som förändring av stad och klimat kan medföra. Målet är att identifiera faktorer som kan förbättra samverkan mellan markavvattnings-företag och kommuner. Metod: Studien utgår ifrån en fallstudie som består av kommuner som har samverkat med markavvattningsföretag. De datainsamlingsmetoder som använts för att besvara frågeställningarna är litteraturstudier och semistrukturerade intervjuer med kommuner som har erfarenhet av sådana samverkansprocesser; Linköping och Norrköping. Resultat: De faktorer som kan förbättra samverkan är framförallt kommunikationen mellan parterna för att finna ömsesidiga nyttor och att uppdatera registren över markavvattningsföretag. Fallstudien har visat att förbättring av samverkan kan uppnås genom rådgivningsstöd från en transparent aktör. Norrköpings kommun önskar bland annat en enkel handbok som är framtagen av någon myndighet för att få det transparent och som är anpassad för aktörer med mindre kännedom kring processen. Fallstudien har även påvisat att markavvattningsföretag är en intressent som har hög angelägenhet att påverka projekt samtidigt som de har makt att styra projektets tidsaspekt. Dessa är projektets nyckelintressenter som är viktiga aktörer för projektets helhet och som måste prioriteras, hållas informerade och nöjda för att underlätta samverkan. För att upprätthålla en hållbar stadsutveckling behöver översvämnings- och föroreningsrisker minskas för att skydda naturresurser och bevara den biologiska mångfalden. Öppna diken mildrar belastningen på avloppssystemen som i sin tur minskar risker för översvämningar och främjar biologisk mångfald. Konsekvenser: Kännedom om betydelse av användandet av öppna diken är nödvändigt för att upprätthålla hållbar stadsutveckling. Det saknas uppgifter i registren över markavvattningsföretag eftersom de inte är uppdaterade. Det kan därmed bli ett detektivarbete för kommuner att komma fram till rätt person. Denna problematik medför även att en del markavvattningsföretag saknar kännedom om dess roll i projekten. Det finns dessutom ingen myndighet att rådfråga i dessa samverkansprojekt. Begränsningar: Det var endast kommuner med erfarenheter av dessa projekt som inkluderades i undersökningen eftersom frågeställningarna krävde viss kännedom om markavvattningsföretag. Det var även lämpligt att endast ta hänsyn till faktorer som berör samverkansprocessen, utan att studera övriga påverkande aspekter såsom jordens permeabilitet eller växters vattenupptag eftersom detta inte påverkar studiens utfall. / Purpose: Focus on stormwater management is important because water pollution and flood risks are increasingly anticipated effects of climate change and urbanization. In case of urban growth areas, municipalities want to exploit the existing ditches rather than install new pipes. Here cooperation with agricultural drainage organizations may be required. This study contains exposition of key factors to facilitate such cooperation’s to support sustainable urban development. The purpose of this study is to facilitate the cooperation between agricultural drainage organizations and municipalities in order to avoid flooding and pollution which urbanization and climate change can result in. The objective is to identify factors that can help improve cooperation between agricultural drainage organizations and municipalities. Method: The study was carried out as a case study of municipal cooperation with agricultural drainage organizations. Data was collected from literature studies and semi-structured interviews with municipalities with previous such experiences; Linköping and Norrköping. Findings: The factors that can improve cooperation are foremost communication between both parties in order to find mutual benefits and to keep the registers over agricultural drainage organizations updated. This case study has shown that improvement of collaboration can be achieved through counseling support from a transparent actor. Norrköping Municipality wishes for a simple handbook accessible even to actors with little to no prior knowledge about the process. The case study has also shown that agricultural drainage organizations are stakeholders who have a high interest in influencing projects while also having the power to control the project's time aspect. These are the key stakeholders of the project, who are important players for the project as a whole and who must be prioritized, kept informed and satisfied to facilitate collaboration. To maintain sustainable urban development the risks of flooding and water pollution need to be minimized to protect biodiversity. Open ditches mitigate the load on drainage systems which reduces the risk of flooding and support biodiversity. Implications: Knowledge of the importance in using open ditches is necessary to maintain sustainable urban development. There is data missing in the registers over agricultural drainage organizations since they are not updated. This results in difficulties for municipalities when trying to reach the correct person. This problem also results in some agricultural drainage organizations missing knowledge of their part in projects. There is also no authority to consult in these cooperative projects. Limitations: The study does not consider other aspects beside the cooperation between municipalities and agricultural drainage organizations. Only municipalities with prior experience of working with agricultural drainage organizations were questioned as the questions required certain knowledge about these processes. It was also appropriate to only consider factors that affect the cooperative process without studying other affecting aspects like the permeability or water uptake of plants since this does not affect the results of the study.

Metoden för att avgränsa modellområdet i delavrinningsområden med homogena hydrologiska parametrar inför hydrauliska ledningsnätssimuleringar kan vara tidsödande. Olika metoder och tillvägagångssätt finns att tillgå, men kunskapen om hur valet av avgränsningsmetod påverkar simuleringsresultaten är begränsad.   I examensarbetet undersöktes hur fyra enkla avgränsningsmetoder, i jämförelse med två detaljerade metoder, påverkade en hydraulisk simulering av en regnhändelse på sex olika modelluppsättningar av spill- och dagvattennät. De detaljerade metoderna byggde på information om markhöjder i kombination med byggnaders placering, medan de enklare metoderna byggde på information om markhöjder respektive Thiessenpolygoner. Avgränsningsmetoderna testades för en dagvattenmodell, en kombinerad spill- och dagvattenmodell, och fyra spillvattenmodeller. Alla modellparametrar förutom de associerade med delavrinningsområdena (bidragande yta, koncentrationstid) hölls konstanta medan en regnhändelse med återkomsttid tio år och en maximal regnintensitet av 22,8 µm/s (82.1 mm/h) simulerades för varje avgränsningsmetod och modelluppsättning.    De olika metoderna gav upphov till skillnader i simulerat maximalt vattendjup i modelluppsättningarnas brunnar. De enklare metoderna tenderade att underskatta de simulerade vattendjupen och avvikelsen mot de detaljerade metoderna översteg 0,1 m, vilket utgjort en gräns för när avvikelsen får praktisk betydelse. Fler avvikelser erhölls uppströms i ledningsnätet och för modelluppsättningar med större avrinningsbildning. Inga entydigt upprepande förhållanden mellan metodernas påverkan på simuleringsresultaten mellan modelluppsättningarna fanns, varvid modellområdesegenskaper tros påverka effekten av vald avgränsningsmetod. Resultaten indikerade att det kan vara mer motiverat att använda enklare avgränsningsmetoder för spillvattenmodeller i förortsmiljö än för dagvattenmodeller i stadsmiljö, samt att metoder baserat på Thiessenpolygoner ger bättre överensstämmelse mot detaljerade metoder än de topografibaserade. / The method of delineating a model into sub-catchments with homogenous hydrological parameters, before performing hydraulic simulations, can be tedious work. Different approaches and methods for this purpose exist, but the understanding for how the choice of delineation method affects the modeling process and in the end the simulation results is limited.    This thesis explored how four simplified delineation methods, in comparison with two detailed methods, affected hydraulic simulation of a rain event on six different model set ups. The detailed methods were based on terrain analysis and property boundaries. The simplified methods were composed of twomethods based on terrain analysis of elevation models, and two methods based on Thiessen polygons. The delineation methods were applied on one stormwater model, one combined storm- and wastewater model, and on four wastewater models. All model parameters except for those associated with the sub-catchments (time of concentration, imperviousness) were kept constant as a scenario of a rain event with a return time period of 10 years and maximum intensity of 22.8 µm/s (82.1 mm/h) were simulated for every delineation method and model set up.   The different methods resulted in differences in simulated maximal water depth in the modelled manholes. The simplified methods tended to underestimate the water depth. Additionally, the deviation from the detailed methods exceeded 0.1m, which is a threshold value for when the deviations will be of practical importance. Greater deviations occurred upstream in the sewer system and for models with greater runoff volume. No unambiguous patterns were found between the methods and the model setups. Hence, the delineation methods cannot by themselves explain the observed deviation in the simulated water depths. The results indicate that it is more suitable to apply a simple method on a sewage model in a suburban area, than for a stormwater model in an urban area. In addition, the simplified methods based on Thiessen polygons showed more agreement with the detailed methods than the simple methods based on terrain analysis.

abstract: The rate of urbanization has been impacted by global economic growth. A strong economy results in more people moving to already crowded urban centers to take advantage of increased employment opportunities often resulting in sprawling of the urban area. More natural land resources are being exploited to accommodate these anthropogenic activities. Subsequently, numerous natural land resources such as green areas or porous soil, which are less flood-prone and more permeable are being converted into buildings, parking lots, roads and underground utilities that are less permeable to stormwater runoff from rain events. With the diminishing of the natural landscape that can drain stormwater during a rainfall event, urban underground drainage systems are being designed and built to tackle the excess runoff resulting from urbanization. However, the construction of a drainage system is expensive and usually involves massive land excavations and tremendous environmental disturbances. The option for constructing an underground drainage system is even more difficult in dense urban environments due to the complicated underground environments, creating a need for low footprint solutions. This need has led to emerging opportunities for low impact development (LID) methods or green infrastructures, which are viewed as an environmentally friendly alternative for dealing with stormwater runoff. LID mimics the pre-development environment to retain the stormwater runoff through infiltration, retention, detention and evaporation. Despite a significant amount of prior research having been conducted to analyze the performance of runoff volume reduction and peak flow decrement of various green infrastructures, little is known about the economic benefits of using LID practices. This dissertation fills the gap in the knowledge regarding the life-cycle-cost effectiveness of green infrastructure in current urban developments. This study’s two research objectives are: (1) Develop a life cycle cost calculation template to analyze the cost benefits of using LID compared to the traditional drainage system (2) Quantify the cost benefits based on the real-world construction projects A thorough literature review led to the data collection of the hydrological benefits of using LIDs in conjunction with overviewing three real-world construction projects to quantify the cost benefits of LIDs. / Dissertation/Thesis / Doctoral Dissertation Civil, Environmental and Sustainable Engineering 2019

Urbanization and increase of impervious areas impact stormwater runoff and can pollute receiving waters. Total suspended solids (TSS) are of particular concern as they can act as a transport agent for other pollutants. Moreover, the existence of the first flush phenomenon (FF), whereby the first stage of storm runoff is the most concentrated, can also have profound ecological effects on receiving waters. Understanding the various types of pollutants in watershed stormwater, their correlation with rainfall parameters (precipitation depth and previous dry days) and with TSS, and the existence of FF is crucial to the design of the most suitable structural best management practice (BMP) that can mitigate their harm. Personal Computer Storm Water Management Model (PCSWMM) is a well-known computer model that can simulate urban runoff quantity and quality and model BMPs. The use of PCSWMM to simulate the first flush phenomenon and to evaluate the effectiveness of structural BMPs has not been previously investigated for a large urban watershed with seriously polluted stormwater runoff. This research is concerned with the study of a framework for designing structural best management practices (BMPs) for stormwater management in a large watershed that is based on comprehensive analysis of pollutants of concern, rainfall parameters of influence, and the existence of FF. The framework was examined using the PCSWMM computer model in the St Anthony Park watershed, an urban watershed in St Paul, Minnesota with a large drainage area of 3,418 acres that discharges directly into the Mississippi River via a storm tunnel. A comprehensive study was undertaken to characterize the overall St. Anthony Park watershed stormwater quality trends for the period of record 2005-2013 for heavy metals, nutrients (ammonia and total phosphorus), sediment (TSS), and bacteria (E. coli). Stormwater was found to be highly contaminated as measured by exceedance of the Minnesota Pollution Control Agency (MPCA) water quality standards and as compared to data obtained from the National Stormwater Quality Database (NSQD). None of the examined parameters significantly correlated with precipitation depth. Concentrations of most heavy metals, total phosphorus and TSS positively correlated with previous dry days, and most pollutants correlated positively with TSS, which provided a strong rationale for using TSS as a representative pollutant in PCSWMM and in examining BMP efficiency. Moreover, BMPs that targeted the particulate fraction in stormwater would be the most efficient in reducing stormwater pollution. A PCSWMM model was built based on the existing drainage system of the watershed, which consisted of inlet structures, manholes, pipes and deep manholes that connect the network pipes to a deep drainage tunnel discharging directly into Mississippi River. The model was calibrated and validated using recorded storm and runoff data. FF was numerically investigated by simulating pollutant generation and washoff. Using three different numerical definitions of FF, the existence of FF could be simulated, and was subsequently reduced by simulating extended dry detention ponds in the watershed. Extended dry detention ponds (EDDPs) are basins whose outlets are designed to detain stormwater runoff for a calculated time that allows particles and associated pollutants to settle. Extended dry detention ponds are a potential BMP option that could efficiently control both water quantity (by diverting initial volumes of stormwater, thus addressing FF) and quality (by reducing suspending pollutants, thus addressing TSS and co-contaminants). Moreover, they are the least-expensive stormwater treatment practice on a cost per treated unit area. Two location-based designs were examined. The first was an EDDP at the main outfall (OFmain), while the second was a set of seven smaller EDDPs within the vicinity of deeper manholes of the deep tunnel (distributed EDDPs). Distributed EDDPs were similar to the OFmain EDDP at reducing peak stormwater flow (52-61%) but superior in reducing TSS loads (20-25% for small particles and 43-45% for larger particles based on the particle sedimentation rate removal constant k) and in reducing peak TSS loads (67-75%). These efficiencies were obtained using the dynamic and kinematic wave routing methods, indicating that they could be used interchangeably for this watershed. The steady state routing method produced unrealistic results and was subsequently excluded from FF analysis. Finally, distributed EDDPs were superior to OFmain EDDP at eliminating FF per the stringent fifth definition (Δ > 0.2). This was true for small values of k. However, larger values of k and other FF tests (above the 45º no-flush line and FF coefficient b < 1) showed that BMP implementation overall failed to completely eliminate FF. This suggested that the extended time required by EDDPs to efficiently remove pollutants from stormwater via settling would compromise their ability to completely eliminate FF. In conclusion, a comprehensive framework was applied so as to better design the most efficient BMPs by characterizing the overall St. Anthony Park watershed stormwater pollutants, their correlation with rainfall parameters and with TSS, and the magnitude of FF. A cost-effective, rapid, and accurate method to simulate FF and study the optimal BMP design was thus implemented for a large urban watershed through the PCSWMM model.

The response of a karst aquifer to storm events is often faster and more severe than that of a non-karst aquifer. This distinction is often problematic for planners and municipalities, because karst flooding does not typically occur along perennial water courses; thus, traditional flood management strategies are usually ineffective. The City of Bowling Green (CoBG), Kentucky is a representative example of an area plagued by karst flooding. The CoBG, is an urban karst area (UKA), that uses Class V Injection Wells to lessen the severity of flooding. The overall effectiveness, siting, and flooding impact of Injection Wells in UKA’s is lacking; their influence on groundwater is evident from decades of recurring problems in the form of flooding and groundwater contamination. This research examined Class V Injection Wells in the CoBG to determine how Injection Well siting, design, and performance influence urban karst hydrology. The study used high-resolution monitoring, as well as hydrologic modeling, to evaluate Injection Well and spring responses during storm and baseflow conditions. In evaluating the properties of the karst aquifer and the influences from the surrounding environment, a relationship was established between precipitation events, the drainage capacity of the Injection Wells, and the underlying karst system. Ultimately, the results from this research could be used to make sound data-driven policy recommendations and to inform stormwater management in UKAs.

I evaluated the effectiveness of plant roots to increase infiltration rates within stormwater bioretention facilities (SBFs), roadside planter compartments that filter stormwater. SBFs attenuate harmful effects of stormwater by reducing peak flow and retaining pollutants, with increased infiltration that improves both these functions. Researchers have shown that roots can increase infiltration within greenhouse, lab, field, and test SBF settings. However, no researchers have yet measured either the extent to which different root characteristics can increase infiltration or the variation in root characteristics and their effect on infiltration rates among plant assemblages within currently functioning SBFs. To determine if root-enhanced infiltration was occurring within SBFs, I hypothesized 1) there is a relationship between root characteristics and infiltration during late spring, and 2) seasonal root growth increases infiltration rates. Within Portland, OR, I measured infiltration rate from January 2014 to February 2015 and root characteristics from January-February (J-F) and May-June (M-J) 2014 in ten SBFs with "Elk Blue" rush (Juncus patens) and 1 or 2 trees of less than 8.4 cm stem diameter. During M-J, four root characteristics showed a positive relationship with infiltration rate, and two root characteristics showed a strong positive relationship with infiltration rate within the topsoil. Also, a relationship was shown between the increase (J-F to M-J 2014) in three root characteristics and the increase in infiltration rate. To determine if root morphology and infiltration rates differed among SBFs with two different dominant vegetation taxa (small and large root biomass), I hypothesized 3) Juncus patens and tree dominant assemblage (greater root biomass) exhibits greater infiltration compared to the Carex dominant assemblage, 4) the increase in infiltration rate and root characteristics from J-F to M-J is greater in the Juncus compared to the Carex assemblage, and 5) root surface area density (RSAD) within Juncus SBFs shows a positive relationship with infiltration rate in late spring. I measured infiltration rate from January 2014 to February 2015 and root characteristics from January-February (J-F) and May-June (M-J) 2014 among five large-root (Juncus and tree) and five small-root biomass (Carex sp) SBFs. Juncus SBFs showed greater values for three root characteristics during J-F and five root characteristics during M-J 2014 compared to Carex SBFs. Also, Juncus SBFs showed an increase from J-F to M-J 2014 for five root characteristics while Carex SBFs showed no root increase. Juncus SBFs showed a relationship with four root characteristics and Carex SBFs a showed relationship with one root characteristic and infiltration rate. This work strongly suggests plant roots increase infiltration, and thus the primary functions of SBFs. Different root characteristics appear to increase infiltration rate at different depths. Data also show larger-root biomass plants increase infiltration rate to a greater degree than smaller-root biomass plants. I recommend considering several site and facility characteristics when determining the potential for root-enhanced infiltration. When selecting plant species to enhance infiltration, I recommend using several criteria, determining root characteristic values at certain depths, considering installation approaches, and accounting for regional climate changes.

Decisions of adopting best management practices made on residential properties play an important role in reduction of nutrient loading from non-point sources into Lake Champlain and other waterbodies in Vermont. In this study, we use Bayesian belief network (BBN) to analyze a 2015 survey dataset about adoption of six types of green infrastructures (GSIs) in Vermont’s residential areas. Learning BBNs from physical probabilities of the variables provides a visually explicit approach to reveal the message delivered by the dataset. Using both unsupervised and supervised machine learning algorithms, we are able to generate networks that connect the variables of interest and conduct inference to look into the probabilistic associations between the variables. Unsupervised learning reveals the underlying structures of the dataset without presumptions. Supervised learning provides insights for how each factor (e.g. demographics, risk perception, and attribution of responsibilities) influence individuals’ pro-environmental behaviors. We also compare the effectiveness of BBN approach and logistic regression in predicting the pro-environmental behaviors (adoption of GSIs). The results show that influencing factors for current adoption vary by different types of GSI. Risk perception of stormwater issues are associated with adoption of GSIs. Runoff issues are more likely to be considered as the governments’ (town, state, and federal agencies) responsibility, whereas lawn erosion is more likely to be considered as the residents’ own responsibility. When using the same set of variables to predict pro-environmental behaviors (adoption of GSI), BBN approach produces more accurate prediction compared to logistic regression.

Stormwater runoff from developed land is a source of pollution and excessive flow to waterways. The most commonly employed practices for flow and volume control are stormwater ponds and basins (also referred to as detention and retention ponds). These structures can be effective at controlling peak discharge to water bodies by managing flow timing but are often ineffective at removing nutrients, particularly in dissolved forms. Pond morphology coupled with place-specific characteristics (like soil type and drainage area characteristics) may influence plant community composition in these water bodies. The interaction of physical, chemical, and biological elements in stormwater ponds may affect their water quality performance in more significant ways than previously understood. Floating treatment wetlands (FTW) are floating rafts of vegetation that can be constructed using a variety of materials and are an emerging technology aimed at improving the pollutant removal and temperature control functions of stormwater ponds. Previous studies with field research in subtropical and semiarid climatic regions found incremental nutrient removal improvement correlated with FTW coverage of pond surface area. However, data on their performance in cold climates is lacking from the literature. This dissertation presents data from a three-year study examining the performance of FTW on stormwater pond treatment potential in cold climate conditions and optimal vegetation selection based on biomass production, phosphorus (P) uptake, and root architectural characteristics that enhance entrapment functionality. To put the FTW pond performance data into context, results from a survey of seven permitted stormwater ponds in Chittenden County, Vermont and the ponds' associated variability in influential internal and external dynamics are also discussed. Pond morphology, drainage area land use, soil types, and biological communities are analyzed for correlative relationships to identify design factors that affect pond performance but are not controlled factors in stormwater system permitting.