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Author: Brantley Allison Thames Publisher: ISBN: Category : River sediments Languages : en Pages :
Book Description
Urbanization causes flow and sediment regime changes, which leads to alterations in the bed sediment characteristics and degradation of the ecological habitat. Evidence shows that changes in the characteristics of streambed sediment occur in urbanized watersheds; however a link between urbanization and changes in streambed sediment is not well established in the literature. Limited support in the literature does suggest that urbanization is linked to a decline in the diversity of algae, invertebrate, and fish populations. Relationships between urbanization and bed sediment characteristics were explored by three studies using the AnnAGNPS and CONCEPTS models. AnnAGNPS is a GIS-based sediment delivery model with land erosion rates determined by the revised Universal Soil Loss Equation (RUSLE) and sediment yield rates determined by the Hydrogeomorphic USLE (HUSLE) for watersheds primarily dominated by agricultural land use. CONCEPTS is a sediment transport and channel adjustment model that routes sediment input from AnnAGNPS and sediment inputs from channel bed and bank erosion. Both models were developed by the United States Department of Agriculture -- Agricultural Research Service (USDA ARS). The research objectives for this project included: 1) conducting a sensitivity analysis of the AnnAGNPS and CONCEPTS models to evaluate the significance of various model inputs that incorporate the mosaic of urban land use and require field measurements for the non-urbanized and urbanized subwatersheds, 2) producing and executing several combinations of model run simulations with altered runoff and erosion from the hillslope using the entire AnnAGNPS-CONCEPTS modeling couple to simulate varying levels of urbanization, and 3) evaluating AnnAGNPS model results of 15 urban and non-urban subwatersheds ...
Author: Brantley Allison Thames Publisher: ISBN: Category : River sediments Languages : en Pages :
Book Description
Urbanization causes flow and sediment regime changes, which leads to alterations in the bed sediment characteristics and degradation of the ecological habitat. Evidence shows that changes in the characteristics of streambed sediment occur in urbanized watersheds; however a link between urbanization and changes in streambed sediment is not well established in the literature. Limited support in the literature does suggest that urbanization is linked to a decline in the diversity of algae, invertebrate, and fish populations. Relationships between urbanization and bed sediment characteristics were explored by three studies using the AnnAGNPS and CONCEPTS models. AnnAGNPS is a GIS-based sediment delivery model with land erosion rates determined by the revised Universal Soil Loss Equation (RUSLE) and sediment yield rates determined by the Hydrogeomorphic USLE (HUSLE) for watersheds primarily dominated by agricultural land use. CONCEPTS is a sediment transport and channel adjustment model that routes sediment input from AnnAGNPS and sediment inputs from channel bed and bank erosion. Both models were developed by the United States Department of Agriculture -- Agricultural Research Service (USDA ARS). The research objectives for this project included: 1) conducting a sensitivity analysis of the AnnAGNPS and CONCEPTS models to evaluate the significance of various model inputs that incorporate the mosaic of urban land use and require field measurements for the non-urbanized and urbanized subwatersheds, 2) producing and executing several combinations of model run simulations with altered runoff and erosion from the hillslope using the entire AnnAGNPS-CONCEPTS modeling couple to simulate varying levels of urbanization, and 3) evaluating AnnAGNPS model results of 15 urban and non-urban subwatersheds ...
Author: Benjamin Douglas Plumb Publisher: ISBN: Category : Bed load Languages : en Pages : 170
Book Description
Urbanization is known to change the hydrologic and sediment supply regimes of rivers, causing more frequent, flashier flood events (hydromodification) and a reduction and redistribution of sediment sources. Presently, the impact that these changes have on bedload transport in gravel-bed channels and the resulting impact on bed morphology remains largely unknown due to a lack of process based studies. A better understanding of how riverbed form and processes evolve with urbanization is critical as they are a primary factor in controlling stream stability, providing habitat for aquatic species and influencing flood elevations. Additionally, stream rehabilitation is becoming increasingly common in urban rivers and an understanding of how sediment transport dynamics change with the alterations common to urbanization is critical for a successful design. This thesis explores the impact of urbanization, which is the combination of hydromodification and alterations to sediment supply, on the morphodynamics (linkages between channel form and process) of bedforms in gravel-bed rivers. Specific objectives are: 1) to determine if detectable differences in bed morphology exist between rural and urban rivers in the same hydrophysiographic region; 2) to characterize the sediment transport dynamics of a highly urbanized channel; 3) to investigate the differences in geomorphically significant flows and sediment transport characteristics for different levels of watershed urbanization; and 4) to generalize field specific results using a mobile-bed laboratory flume to investigate the sediment transport characteristics for different levels of watershed hydromodification. Longitudinal profiles of 11 rural and 9 urban watercourses with pool-riffle dominated morphologies in the same hydrophysiographic region (Southern Ontario, Canada) were investigated using three objective bedform identification methods; zero-crossing analysis, bedform differencing technique and residual pool depth analysis, as well as visual field identification. Results indicate that urban rivers possess deeper pools and a more topographically variable bed. A field investigation was undertaken to characterize event-based sediment transport dynamics of a highly urbanized gravel-bed river over a three year period. Mimico Creek, located in Toronto, Ontario, Canada, is nearly fully urbanized and lacks significant stormwater management controls, therefore making it a representative study reach. Bedload transport was measured using both active and passive sampling methods to characterize the mobility and transport dynamics of the entire range of surface particles. During this time, over 10 floods were sampled ranging from the approximate threshold discharge to well over the bankfull discharge. Coarse particle mobility differed from that previously reported in literature for rivers with more natural flow regimes. A strong link was found between coarse particle mobility and the transport dynamics of finer material which tends to dominate the bedload. The measured bedload transport data were also used to calibrate a fractional sediment transport model which was combined with hydrometric data corresponding to different levels of watershed urbanization to perform a geomorphic work analysis. Urbanization is increasing the frequency, volume and time of competent discharge events (capable of performing work on the channel). Greater increases of intermediate discharge events were observed. Less urban streams are more influenced by larger discharge events, while urbanization is shifting the geomorphic significance to lower (but still competent) discharges. Inspired from the field observations, an unsteady flow laboratory experiment was conducted to provide more generalized results. Three land-use scenarios representing different levels of watershed urbanization were developed from measured hydrometric data. Results show that both unsteady bedload transport dynamics and resulting bed morphology change with different levels of urbanization. Shorter duration hydrographs (corresponding to urban conditions) possess higher transport rates, less pronounced bedload hysteresis loops and more topographic variability of the bed. A proposed parameter for evaluating the degree of hysteresis shows sediment transport is closely linked with falling limb dynamics. The key conclusion from the field, modeling and laboratory studies is that bedforms in gravel-bed rivers appear to be evolving to a state with more topographic variability. This variability is hypothesized to be additional form roughness to dissipate energy introduced due to hydromodification. These results are unique in literature and further our understanding of urban river processes.
Author: National Research Council Publisher: National Academies Press ISBN: 0309125391 Category : Nature Languages : en Pages : 611
Book Description
The rapid conversion of land to urban and suburban areas has profoundly altered how water flows during and following storm events, putting higher volumes of water and more pollutants into the nation's rivers, lakes, and estuaries. These changes have degraded water quality and habitat in virtually every urban stream system. The Clean Water Act regulatory framework for addressing sewage and industrial wastes is not well suited to the more difficult problem of stormwater discharges. This book calls for an entirely new permitting structure that would put authority and accountability for stormwater discharges at the municipal level. A number of additional actions, such as conserving natural areas, reducing hard surface cover (e.g., roads and parking lots), and retrofitting urban areas with features that hold and treat stormwater, are recommended.
Author: Jie Liang Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Comprehending the response of microbial communities in rivers along urbanization gradients to hydrologic characteristics and pollution sources is critical for effective watershed management. However, the effects of complex factors on riverine microbial communities remain poorly understood. Thus, we established a bacteria-based index of biotic integrity (Ba-IBI) to evaluate the microbial community heterogeneity of rivers along an urbanization gradient. To examine the response of Ba-IBI to multiple stressors, we employed a Bayesian network based on structural equation modeling (SEM-BN) and revealed the key control factors influencing Ba-IBI at different levels of urbanization. The findings indicated that nutrients in water exerted the most significant direct impact on Ba-IBI (r = -0.563), with nitrogen loading, particularly ammonia nitrogen, emerging as the primary direct driver of microbial community heterogeneity in the Liuyang River basin. In addition, our study confirmed the substantial adverse effects of urbanization on river ecology, as urban land use had the greatest indirect effect on Ba-IBI (r = -0.460). Specifically, the discharge load from wastewater treatment plants (WWTP) was found to have a significant negative impact on the Ba-IBI of the entire watershed. In the low urbanized watersheds, rice cultivation (RC) and concentrated animal feeding operations (CAFO) are key control factors, and an increase in their emissions can lead to a sharp decrease in Ba-IBI. In moderately urbanized watersheds, the Ba-IBI tended to decrease as the level of RC emissions increased, while in those with moderate RC emissions, an increase in point source emissions mitigated the negative impact of RC on Ba-IBI. In highly urbanized watersheds, Ba-IBI was not sensitive to changes in stressors. Overall, our study presents a novel approach by integrating Ba-IBI with multi-scenario analysis tools to assess the effects of multiple stressors on microbial communities in river sediments, providing valuable insights for more refined environmental decision-making.
Author: National Research Council Publisher: National Academies Press ISBN: 0309082951 Category : Science Languages : en Pages : 449
Book Description
The Clean Water Act (CWA) requires that wetlands be protected from degradation because of their important ecological functions including maintenance of high water quality and provision of fish and wildlife habitat. However, this protection generally does not encompass riparian areasâ€"the lands bordering rivers and lakesâ€"even though they often provide the same functions as wetlands. Growing recognition of the similarities in wetland and riparian area functioning and the differences in their legal protection led the NRC in 1999 to undertake a study of riparian areas, which has culminated in Riparian Areas: Functioning and Strategies for Management. The report is intended to heighten awareness of riparian areas commensurate with their ecological and societal values. The primary conclusion is that, because riparian areas perform a disproportionate number of biological and physical functions on a unit area basis, restoration of riparian functions along America's waterbodies should be a national goal.
Author: Bruce L. Rhoads Publisher: Cambridge University Press ISBN: 1108173780 Category : Science Languages : en Pages : 544
Book Description
Rivers are important agents of change that shape the Earth's surface and evolve through time in response to fluctuations in climate and other environmental conditions. They are fundamental in landscape development, and essential for water supply, irrigation, and transportation. This book provides a comprehensive overview of the geomorphological processes that shape rivers and that produce change in the form of rivers. It explores how the dynamics of rivers are being affected by anthropogenic change, including climate change, dam construction, and modification of rivers for flood control and land drainage. It discusses how concern about environmental degradation of rivers has led to the emergence of management strategies to restore and naturalize these systems, and how river management techniques work best when coordinated with the natural dynamics of rivers. This textbook provides an excellent resource for students, researchers, and professionals in fluvial geomorphology, hydrology, river science, and environmental policy.
Author: Brantley Allison Thames
Author: Brantley Allison Thames
Author: Vijay P. Singh
Author: James F. Coles
Author: Benjamin Douglas Plumb
Author: Maqbool Ahmad
Author: National Research Council
Author: Jie Liang
Author: Dean C. Snidow
Author: National Research Council
Author: Bruce L. Rhoads