The stream differences extend to the morphology of the banks. The contribution from the banks was greater at Six Mile Creek, where the banks are much steeper and have visible erosion surfaces that contribute sediment to the streams. The bank pins showed net erosion from the banks, which confirm observations made in the field that mass wasting events occurred frequently throughout the study period. This happened during the spring and summer, when the higher stream discharges would erode bank material. Due to the steepness of the banks at Six Mile Creek, the recession limbs of the hydrographs would rarely deposit sediment on the banks. This was not the case at Money Creek; the gentle slopes of the banks meant that when the stream was at bankfull, the water flowed onto the floodplain. In this scenario, when the waters receded and returned to baseflow, sediment was deposited on the stream banks. This was confirmed by the burying and subsequent rediscovery during fall of the bank pins at this stream. The difference in channel morphologies at these streams can potentially lead to interesting implications for the dynamics of sedimenttransport. While representing only one point in a spatially extensive watershed, steeper, eroding banks characterize a larger portion of Six Mile Creek (STREAMS, 2005).
nels has also been observed during large flood events on other streams (Guan et al., 2015). A comparison of the measured hydrographs and the physical and geometrical characteris- tics of the stream channels shows that, for the HOAL exper- iment, there is an extremely high flood wave transformation, with relatively low retention. This is partly due to the de- creasing longitudinal slope of the river bed, and partly due to the higher surface roughness of the natural stream channel. It shows that the transport capacity of the generated waves was exceeded and the amount of transported sediment decreases along the monitored course. In the Nuˇcice experiment, the flood wave transformation was considerably lower. However, we observed relatively significant water retention in the first experiment in September (see the section in the Results refer- ring to mathematical hydraulic modelling). We conclude that the transport capacity of the flood wave was exceeded dur- ing the HOAL experiment, and detached sediment from up- per, steeper parts of the experimental course was redeposited downstream, as in most of the natural streams monitored by Naden et al. (2016). By contrast, during our experiment in Nuˇcice, the transport capacity of the flood waves was not reached, either in September or March. The sediment con- centrations and also the fluxes therefore increased continu- ously throughout the section.
The Corps of Engineers defined the analytical methodology for calculating the design discharge using long term (>10 yrs) discharge frequency and sedimenttransport data for the formation of a sediment rating curve. The method makes use of the effective discharge for channel design, since this value has been shown to have more analytical qualities than analog reference reach dynamic equilibrium values (Doyle et al., 2007). The frequency of effective discharge in the Coastal Plain has not been adequately quantified, nor the accuracy of using bankfull flow as the dominant discharge. Streams frequently overtop their banks in the lowland areas and marshes, at a rate of a few times per year. Stream restoration requires a greater understanding of the relationship between the channel-forming discharge and recurrence interval flow patterns for future design work in the Coastal Plain (Doll et al., 2004). The link between recurrence interval, bankfull flow, and the effective discharge are highly debatable in lower coastal plain and tidewater regions.
al. 2006, Gurnell et al. 2006, Wharton et al. 2006), they constitute a significant store of fine sediment.
2.2.4 Storage within the channel
River channel beds are not generally considered a major depositional environment over geologic time-scales (Leeder 1999). However, significant fine sediment deposits can form in areas where water velocities and turbulence decrease, either naturally (e.g. downstream fining, fluvial lakes) or due to anthropogenic influences (e.g. dams, reservoirs, and weirs). In these areas, sedimentation can pose a significant problem to navigation, the functioning of engineering structures, as well as environment/human health because of contaminants (Mehta et al. 1989b, Luoma & Rainbow 2008, Droppo et al. 2009). In small streams they can still represent a significant temporary sink/source of fine sediment over shorter time periods (i.e. months or years). Estimates for the amount of fine sediment stored within the gravel beds of chalk rivers are 920 g m -2 for the River Frome, 1290 g m -2 for the River Lambourn, 1590 g m -2 for the River Piddle, and 2390 g m -2 for the River Tern (Collins & Walling 2007a, b). These represent 19 - 57% of the rivers’ annual fine sediment loads. When the deposits within aquatic macrophytes are included in the analysis, estimates of fine sediment storage increase significantly. Heppell et al. (2009) calculated fine sediment storage between 11.6 and 66.8 kg m -2 for the Bere Stream, and 0.9 and 23.5 kg m -2 in the River Frome. Storage was strongly correlated to the percent cover of macrophytes, and it is macrophyte cover which is responsible for the substantial temporal variations in fine sediment storage. For sediment stored within macrophytes, the permanence of the storage is tied to macrophyte stand dynamics. If the plants die back in the winter, leaving the sediment exposed to bed shear stress and turbulence, it will more likely to be transported away from the reach (Kleeberg et al. 2010). However, if macrophyte stands persist for greater than a year, deposition within the stands will have a more significant impact on sedimenttransport dynamics in these systems.
Fortnightly, cumulative rainfall (R) and throughfall samples under deciduous trees (TH1) and coniferous trees (TH2) were collected using conical, volumetric rain gauges. A ten- bottle sequential rainfall sampler was installed at the rain gauge located within the Weierbach (modified from Kennedy et al., 1979). Three automatic water samplers (ISCO 3700 FS and 6712 FS) were installed immediately upstream of the weir to collect stream water samples (AS) frequently (0.5 to 4 h) during storm events. Sampling was triggered by flow conditions. Events were considered separately if they were separated by a period of at least 24 h without rainfall. Stream water at the catchment outlet (SW) and wells (GW1 to GW4) were sampled fortnightly, as well as prior to, dur- ing, and following precipitation events. Soil water was sam- pled fortnightly using Teflon suction lysimeters, installed at three locations: deciduous hillslope (SS1), coniferous hills- lope (SS2), and riparian zone (SSr). Three soil depths for each location: 10 cm for the organic layer (Ah horizon), 20 and 60 cm for the mineral layers (B and C horizons). Over- land flow (OF) that occurred on lower hillslope was sampled using 1 and 2 m long gutters sealed to the soil surface, which diverted surface runoff to 1 or 2 L plastic, blackened (to pre- vent light penetration which causes diatom growth) water bottles. Note that what we refer to as OF might in fact origi- nate within the forest litter layer (Buttle and Turcotte, 1999; Sidle et al., 2007). All gutters were covered to avoid the in- fluence of precipitation. Gutters were regularly cleaned with Milli-Q water to avoid diatom growth on their surfaces.
In the few cases where the proportion of clay is less than the SDR, only a portion of the delivered sediment is clay and so the nutrient concentration is reduced by the ratio of the proportion of clay to the SDR. In previous projects (Brodie et al., 2003) it was found that the nutrient enrichment ratio simulated by the above equation gave nutrient concentrations signiﬁ cantly higher than those observed in river sediments of the region. The enrichment ratios were also larger than those recorded in ﬁ eld experiments. Thus the eﬀ ect of nutrient enrichment was reduced by half (the 0.5 factor in Equation 1). Data on soil clay proportions and nutrient concentrations for phosphorus and nitrogen were extracted from the Australian Soil Resource Information System (Henderson et al., 2001). The nutrient loads from riverbank erosion were calculated as the product of their respective sediment yields multiplied by the soil nutrient concentration, which for phosphorous was taken to be 0.25 g kg − 1 and for nitrogen 1 g kg − 1 .
Human aortic endothelial cells (HAECs), originally iso- lated from human aorta, were purchased from ScienCell Research Laboratories. Recommended endothelial cell culture medium (ECM, ScienCell Research Laborato- ries, Carlsbad, CA, USA) was used for the culturing of HAECs. HAECs at passages 4–7 were used in all experi- ments. SupT1, ACH2, A3.01, HUT-78HIV, HUT-78, and U1HIV were kindly provided by the NIH AIDS Research Program. SupT1 cells were cultured in RPMI-1640 con- taining 10% FBS and penicillin–streptomycin (100 µg/ ml). ACH2 is a cloned T-lymphocyte cell derived from A3.01 that are chronically infected with HIV, which con- sistently produces a low level of virus particles. ACH2 and A3.01 cells were maintained in RPMI 1640 supple- mented with 10 mM HEPES, penicillin–streptomycin (100 µg/ml), 2 mM l-glutamine and 10% FBS. HUT- 78HIV is a T lymphocyte cell line chronically infected with HIV-1SF2. HUT-78HIV and uninfected HUT-78 cells were grown in RPMI 1640 with penicillin–strep- tomycin (100 µg/ml) and 10% of FBS. U1HIV is a U937 monocytic cell line infected with HIV, which maintains low constitutive expression of virus. U1HIV and U937 cells were maintained in RPMI 1640 supplemented with penicillin–streptomycin (100 µg/ml), 2 mM l-glutamine and 10% FBS. Co-culture of HAECs with HIV-1-infected cells was performed by adding ACH2, U1HIV, or HUT- 78HIV to a monolayer of HAEC in 12 well plates and sub- sequently incubating for 5 days. ACH2 and U1HIV cells were pre-treated with phorbol 12-myristate 13-acetate (PMA, 10 −8 M) for 1–2 days to promote HIV replication.
Now, give the sensor a GPS unit, and let it report surface height instead of temperature. The surface height varies quite rapidly compared with tempera- ture, so we might have the sensor send back a reading every tenth of a second. If it sends a 4-byte real number each time, then it produces 3.5 megabytes per day. It will still take some time to fill up main memory, let alone a single disk. But one sensor might not be that interesting. To learn something about ocean behavior, we might want to deploy a million sensors, each sending back a stream, at the rate of ten per second. A million sensors isn’t very many; there would be one for every 150 square miles of ocean. Now we have 3.5 terabytes arriving every day, and we definitely need to think about what can be kept in working storage and what can only be archived.
Looking to the future, there is a need to continue to improve our understanding of catchment sediment dynamics and their response to land use and climate change and our ability to model catchment behaviour. As management attracts greater attention, it is important that the available models should be capable of predicting catchment response under different management sce- narios, in order to assess their likely impact and success. Sediment source tracing must be seen as providing key information for targeted management and there is a need to exploit the potential for further improve- ments in source discrimination, to identify source-speciﬁc inputs, and to progress its transfer from being a research tool to one that can be more easily and widely applied on a routine basis. To support policy-making it is important that further attention should be directed to establishing more meaningful sediment targets or metrics for assessing catchment compliance and this will require further research on the ecological impacts of ﬁne sediment. In this context, attention should be directed to the relative roles of the organic and inorganic components of ﬁne sediment loads in contributing to sediment-related stress. Developing effective strategies for controlling ﬁne sediment loss to watercourses will require an improved empirical data base on the cost-effectiveness of mitigation options, set in the context of
Agricultural chemical transport to surface water and the linkage to other hydrological compartments, principally ground water, was investigated at ﬁ ve watersheds in semiarid to humid climatic settings. Chemical transport was aﬀ ected by storm water runoﬀ , soil drainage, irrigation, and how streams were linked to shallow ground water systems. Irrigation practices and timing of chemical use greatly aﬀ ected nutrient and pesticide transport in the semiarid basins. Irrigation with imported water tended to increase ground water and chemical transport, whereas the use of locally pumped irrigation water may eliminate connections between streams and ground water, resulting in lower annual loads. Drainage pathways in humid environments are important because the loads may be transported in tile drains, or through varying combinations of ground water discharge, and overland ﬂ ow. In most cases, overland ﬂ ow contributed the greatest loads, but a signiﬁ cant portion of the annual load of nitrate and some pesticide degradates can be transported under base-ﬂ ow conditions. Th e highest basin yields for nitrate were measured in a semiarid irrigated system that used imported water and in a stream dominated by tile drainage in a humid environment. Pesticide loads, as a percent of actual use (LAPU), showed the eﬀ ects of climate and geohydrologic conditions. Th e LAPU values in the semiarid study basin in Washington were generally low because most of the load was transported in ground water discharge to the stream. When herbicides are applied during the rainy season in a semiarid setting, such as simazine in the California basin, LAPU values are similar to those in the Midwest basins.
concentration 1.7 mg/kg, and can be subsequently released into groundwater. In recent times, increased anthropogenic inputs have contributed to geochemical changes in the subsurface that affect the mobilization of arsenic into subsurface water resources. Concentrations above the EPA’s maximum contaminant level (MCL) of 10 µg/L have recently been reported in many areas across the United States, including Nebraska. The health risk of prolonged exposure to high arsenic concentrations are skin ailments, like hyper pigmentation and keratosis, and cancer. Furthermore, many rural communities, especially in western Nebraska, lack the resources to treat their drinking water supplies. Recent studies have indicated As concentrations above the MCL in Wauneta, NE, a small community in western Nebraska. Wauneta is quite concurrent with other well-studied As contaminated regions but exhibits some important hydrological and geological differences including the presence of oxidizing groundwater, carbonate-rich sediments, and the influence of Frenchman Creek, which flows through the town. Sediment geochemical analyses revealed two sources of As: 1) As derived from Frenchman Creek and 2.) As sourced from the aquifer sediments. Sequential extraction experiments indicate that sediments contain as much as 4.22 mg/kg As and have the potential to contaminate the groundwater up to 99.75 µg/L.
have emerged as the most promising topology for high and medium voltage applications for the coming years. However, one particular negative characteristic of MMCs is the existence of circulating current, which contains a dc component and a series of low- frequency even-order ac harmonics. If not suppressed, these ac harmonics will distort the arm currents, increase the power loses, and cause higher current stresses on the semiconductor devices. Repetitive control (RC) is well known due to its distinctive capabilities in tracking periodic signals and eliminating periodic errors. In this paper, a novel circulating current control scheme base on RC is proposed to effectively track the dc component and to restrain the low-frequency ac harmonics. The integrating function is inherently embedded in the RC controller. Therefore, the proposed circulating current control only parallels the RC controller with a proportional controller. Thus, conflicts between the RC controller and the traditional proportional integral (PI) controller can be avoided. The design methodologies of the RC controller and a stability analysis are also introduced. The validity of the proposed circulating current control approach has been verified by simulation and extension can be done using Fuzzy Logic Controller.
The number of European research projects and funding for road transport LNG has contributed to reaching a high TRL. The Cryoshelter project verified the commercial viability of the LNG storage tank, and HDGAS showed that a natural gas engine could achieve a range of 800 km in an HDV. The next steps for LNG for HDVs will address implementing LNG refuelling stations; strategically spread along major transport routes to ensure that LNG fuel is available throughout the journey. For future research, there could be a possibility to replace the LNG/CNG fuels with biomethane, which will further reduce carbon emissions compared to current state-of-the- art natural gas technology. Research is also being done in fuel storage, handling and injection systems, addressing in this way methane leakage. Some recent projects (PEMSFORNANO, DOWNTOTEN and SUREAL 23) suggest NG engines might have higher particle number (PN) emissions than diesel engines; that remains a crucial issue to be addressed if gaseous fuels are introduced as a viable alternative to diesel.
It has been found empirically that for very low flows no sediment motion takes place. If the flow is gradually increased then the hydrodynamic forces on individual particles will eventually become sufficiently large that the particles begin to move. The point at which sediment movement takes place is of interest for a number of problems. If the flows are always below the threshold of motion then no movement or change to the bed profile can be expected. Thus if the flows can be shown to be always below the threshold of motion then all the other aspects of mobile-bed hydraulics can be ignored. As discussed in Chapter 9 the amount of fine sediment that is present in gravel affects the survival of fish eggs. There is thus interest in knowing the flow conditions in which fine sediment will be deposited or the flows needed to ‘clean out’ fine sediments from gravel. The theoretical approach to initiation of motion is also applicable to the estimation of the size of stone rip-rap that will remain stable under given flow conditions.
High order coastal plain rivers in the United States and most other countries are severely impacted by excess nutrients, especially nitrogen, which causes fish kills and human health problems, damages coastal shellfish fisheries, and results in deterioration of recreational uses of our waters (Glasgow and Burkholder 2000, Mallin et al. 2000). Recent research has shown that efforts to improve water quality in receiving waters need to focus on low order streams where the majority of the water comes from. Nutrient processing and retention capacity is highest in these small streams (Peterson et al. 2001). All anthropogenic land uses can strongly influence the supply of nutrients and fine sediment to streams, which impact stream morphological features, algal productivity and fish and invertebrate populations (Lenat 1984, Everest et al. 1987, Lloyd et al. 1987, Swanson et al. 1987, Munn et al. 1989, Osborne and Kovacic 1993, Lenat and Crawford 1994, Richards et al. 1996).
In solving Eq. (14), four type of boundaries (in- flow, outflow, water surface and sediment bed boundary) need to specified. For more study, those refer to Lin and Falconer (1997). The im- portant assumption for a moveable bed contains that in zones where the fluid flow is varying ra- pidly or in (circulation) zones where the velocities are too small to initiate sediment motion, the ap- plication of an instantaneously adjusted equili- brium bed concentration may result in a positive concentration gradient near the bed. In the current model the main focus is the sedimenttransport. A fixed bed was assumed, but mass of bed sediment changes due to erosion and deposition was recovered.
Another fundamental aspect is represented by the influence of rigid and emer- gent plants on flow resistance (Ishikawa, Mizuhara, and Ashida 2000a; James et al. 2004; Kothyari, Hayashi, and Hashimoto 2010; Tanino and Nepf 2008). The rela- tionship between turbulence and drag resistance is one of the most complex issues concerning the interactions plant-flow. Because of its complexity, the research is now moving toward a deeper analysis of the turbulence structure and diffusive transport processes through plants (Ghisalberti and Nepf 2009; Li and Shen 1973; López and García 2001; Nepf and Ghisalberti 2008; Nepf 1999; Takemura and Tanaka 2007). These studies include sedimenttransport processes (mostly sus- pended load transport), diffusion and dispersion of passive and reactive scalars and its implications for water quality problems and for transport processes in rivers. Almost all the investigations which focus on flow field and flow resistance, however, have neglected the contribution of morphological elements related with rigid vegetation in beds. The open question is whether to neglect the contribution due to bed forms is a correct assumption, since in non-vegetated beds the same assumption would be considered a rough approximation.
Sedimenttransport plays a major role in the evolution of river beds and estuaries; consequently it exerts a great influence on the topography evolution of earth‘s surface (Yang, 2005). A lot of natural rivers facing sedimentation problems either caused by erosion or human activities, but some are related to river management that arise from the adequate prediction of sediment behaviour. Any persistent changes of sediment in the rivers transport capacity, due to natural activity will promote erosion and/or deposition as the river responds to those conditions. (Bhuiyan et al, 2009). Sedimentation study is more acquaint with the behaviour of sediment load in a river where it is depends on the types of river bed and migration of bed forms such as ripples and dunes (Gui and Jin, 2002; Van Rijn, 2007).
After detecting the clusters, the second problem deals with validating their quality. Traditional val- idation methods (Halkidi et al., 2002a,b; Tan et al., 2005) evaluate the clustering results by either (i) using some external knowledge about what the clustering model should be and comparing it against the detected clusters, or (ii) by assessing how well the data stream conforms to the detected clusters, or else by judging the clusters’ quality without referring to the data (i.e. internal metrics). For example, the detected clusters should have low similarity with each other (i.e. they are distinct). However, in the evolving data stream scenario, these validation methods are hard to apply because of the evolution of the clusters that can change their properties anytime. For example, if two prod- ucts are known to be similar through external knowledge (e.g. both products are books about data mining), but over time users show different interests in them for different reasons (e.g. one book receives very low ratings), then these products might be classified in two different clusters. By clas- sical external evaluation metrics, the new two clusters will be misjudged of being of low quality, although they might be truly of high quality and really reflect the needs of the users.
Additionally, extended periods of low flow within Onion Creek may have allowed the sediment that had been previously eroded from stream banks to accumulate within the channel. Both of these conditions may have created a supply of previously eroded
sediment within the stream channel that could be easily mobilized and incorporated into the sediment loads of subsequent flow events with sufficient capacity to transport the eroded sediment. Stream bank recession rates and sediment export were both closely related to peak event discharge rates. Over the study period, 79% of the cumulative bank recession and 49% of the sediment export occurred in about 12 days during three major storm flow events. Results from this study add to our understanding of the importance of stream bank erosion as a source of sediment and provide insight into processes controlling the erosion and transport of sediment. This information will aid in planning well-targeted conservation practices to mitigate sediment loading from agricultural watersheds.