<p>Många svenska kommuner har idag problem med överbelastade avloppsledningssystem. Det kan bland annat resultera i källaröversvämningar i närbelägna fastigheter, överbelastade reningsverk eller bräddningar till recipienten. För att motverka dessa effekter kan olika åtgärder vidtas. Åtgärderna kan vara olika lämpliga beroende på typ av område och kostnaderna för genomförandet kan variera kraftigt och ha olika miljöpåverkan. Detta innebär att det är viktigt att väga samman effektiviteten av olika åtgärder, deras miljöpåverkan, kundnytta och kostnad.</p><p>Syftet med examensarbetet var att med hjälp av ett hydrauliskt modelleringsverktyg (PCSWMM) studera ett antal typområden och ta fram en förenklad modell. Modellen ska enkelt kunna anpassas till olika områden och ge en översiktlig bild av situationen i områdets ledningssystem. Därmed kan eventuella överbelastningsproblem lokaliseras och en kostnadseffektiv lösning testas.</p><p>En hydraulisk modell utvecklades för Viksängsvägens avrinningsområde i Södertälje kommun. Det är ett äldre område med underdimensionerade ledningar vilket orsakar problem vid hård belastning. Effekten av olika åtgärder testades i modellen och en kostnadsanalys gjordes för att utreda vilken åtgärd som var mest kostnadseffektiv.</p><p>En grenad modell visade sig ge bäst beskrivning av Viksängsvägens avrinningsområde. Det var en förenklad modell som gick relativt snabbt att sätta upp för ett nytt område och som tog hänsyn till avrinningsvolym, ledningskapacitet och ledningssystemets struktur. Modellen kräver dock en del information om ledningssystemets uppbyggnad och de hårdgjorda ytornas fördelning över området.</p><p>Den åtgärd som rekommenderades för Viksängsvägens avrinningsområde var att bygga utjämningsmagasin i anslutning till Viksängsvägen. Detta för att kostnaden var relativt liten jämfört med andra åtgärder samt för de positiva effekter åtgärden har på miljön och människorna som bor och vistas i området.</p>

Många svenska kommuner har idag problem med överbelastade avloppsledningssystem. Det kan bland annat resultera i källaröversvämningar i närbelägna fastigheter, överbelastade reningsverk eller bräddningar till recipienten. För att motverka dessa effekter kan olika åtgärder vidtas. Åtgärderna kan vara olika lämpliga beroende på typ av område och kostnaderna för genomförandet kan variera kraftigt och ha olika miljöpåverkan. Detta innebär att det är viktigt att väga samman effektiviteten av olika åtgärder, deras miljöpåverkan, kundnytta och kostnad. Syftet med examensarbetet var att med hjälp av ett hydrauliskt modelleringsverktyg (PCSWMM) studera ett antal typområden och ta fram en förenklad modell. Modellen ska enkelt kunna anpassas till olika områden och ge en översiktlig bild av situationen i områdets ledningssystem. Därmed kan eventuella överbelastningsproblem lokaliseras och en kostnadseffektiv lösning testas. En hydraulisk modell utvecklades för Viksängsvägens avrinningsområde i Södertälje kommun. Det är ett äldre område med underdimensionerade ledningar vilket orsakar problem vid hård belastning. Effekten av olika åtgärder testades i modellen och en kostnadsanalys gjordes för att utreda vilken åtgärd som var mest kostnadseffektiv. En grenad modell visade sig ge bäst beskrivning av Viksängsvägens avrinningsområde. Det var en förenklad modell som gick relativt snabbt att sätta upp för ett nytt område och som tog hänsyn till avrinningsvolym, ledningskapacitet och ledningssystemets struktur. Modellen kräver dock en del information om ledningssystemets uppbyggnad och de hårdgjorda ytornas fördelning över området. Den åtgärd som rekommenderades för Viksängsvägens avrinningsområde var att bygga utjämningsmagasin i anslutning till Viksängsvägen. Detta för att kostnaden var relativt liten jämfört med andra åtgärder samt för de positiva effekter åtgärden har på miljön och människorna som bor och vistas i området.

Hydrology Modeling using HEC-HMS (Hydrological Engineering Centre-Hydrologic Modeling System) is accepted globally for event-based or continuous simulation of the rainfall-runoff operation. Similarly, Machine learning is a fast-growing discipline that offers numerous alternatives suitable for hydrology research's high demands and limitations. Conventional and process-based models such as HEC-HMS are typically created at specific spatiotemporal scales and do not easily fit the diversified and complex input parameters. Therefore, in this research, the effectiveness of Random Forest, a machine learning model, was compared with HEC-HMS for the rainfall-runoff process. In addition, Point gauge observations have historically been the primary source of the necessary rainfall data for hydrologic models. However, point gauge observation does not provide accurate information on rainfall's spatial and temporal variability, which is vital for hydrological models. Therefore, this study also evaluates the performance of satellite and radar precipitation products for hydrological analysis. The results revealed that integrated Machine Learning and physical-based model could provide more confidence in rainfall-runoff and flood depth prediction. Similarly, the study revealed that radar data performance was superior to the gauging station's rainfall data for the hydrologic analysis in large watersheds. The discussions in this research will encourage researchers and system managers to improve current rainfall-runoff simulation models by application of Machine learning and radar rainfall data.

Developments that have been taking place on Cal Poly campus over the years have altered the natural hydrology of the area. Stormwater management practices could help reduce the impacts of these developments. Computer models can help to design effective and economical stormwater management solutions at a watershed scale. As such, the objective of this study was to develop a stormwater management model for Cal Poly campus. The model was developed based on the utility data obtained from the university and other watershed data available from open sources. Field surveys were conducted to address some anomalies in the utility data, and streamflow monitoring was performed. The model was calibrated using the streamflow data measured during this study. The calibration effort significantly improved the prediction accuracy of the model. The calibrated model was then used to analyze the hydrologic performance of implementing LID systems for two projects that Cal Poly plans to build. Permeable Pavements (PPs) and Bioretention Cells (BRCs) were the LID types examined. The LIDs were evaluated based on peak flow and runoff volume reductions they would achieve. The potential reductions were compared for current conditions and the proposed project if LIDs were implemented, and for inflows to the LIDs and outflows from the LIDs. The results indicate that implementing a PP system for the proposed student apartment at the current H-1 and R-1 parking lots and a BRC system for the proposed engineering project facilities at the current H-2 parking lots will significantly reduce peak flow and runoff volume. Overall, the developed model will help the university with the traditional stormwater management practices such as flood control and to identify effective LID practices for future developments. Limitations of the current model and recommendations on how to improve the model are also discussed.

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.