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1.
On December 26, 2015 (Boxing Day), an exceptional flood event occurred in the Irwell catchment, United Kingdom, when the neighbouring Mersey catchment experienced a much more typical winter run‐off event. This provided an opportunity to examine the influence of high‐magnitude hydrological processes on the behaviour of fine‐grained metal‐contaminated bed sediments. Forty sites across the two catchments were sampled for channel bed fine sediment storage and sediment‐associated metal(loid) concentrations prior to, and following, the flooding. Sediments were analysed for total As, Cr, Cu, Pb, and Zn and then subjected to a five‐step sequential extraction procedure. Despite a significant reorganisation of fine‐grained (<63 μm) sediment storage, metal(loid) concentrations demonstrated markedly conservative behaviour with no significant difference observed between pre‐flooding and post‐flooding values across both catchments. Estimates of the channel bed storage of sediment‐associated metal(loid)s also showed minimal change as a result of the flooding. The metal partitioning data reveal only minor changes in the mobility of bed sediment‐associated metal(loid)s, indicating that such flood events do not increase the availability of sorbed contaminants in these catchments. Post‐flooding bed sediment metal(loid) loadings remain high, indicating persistent and long‐lasting sources of contamination within the Irwell and upper Mersey fluvial network.  相似文献   

2.
Hugh G. Smith 《水文研究》2008,22(16):3135-3148
Historically upland headwater catchments in south‐eastern Australia have undergone extensive gully erosion that has removed large amounts of sediment to lowlands. Recent research suggests these upland areas may continue to dominate fine sediment loads in lowland rivers. Improved understanding of sediment transfer through upland headwater catchments may have implications for interpreting downstream sediment supply. In this study a nested catchment design was utilized to examine suspended sediment yields and delivery from a small tributary sub‐catchment (1·64 km2) to the study catchment outlet (53·5 km2). Monitoring of suspended sediment concentration and discharge was undertaken for a period of nearly two years and used to estimate suspended sediment loads. Estimated total suspended sediment exports over the period of monitoring were 24·16 t from the sub‐catchment and 550·3 t from the catchment, which are generally less than previous reported small catchment yields in south‐eastern Australia. The extent of sediment delivery was examined using between‐site ratios of specific sediment yield per unit area and incised channel length. Sediment delivery was high under average rainfall conditions, but seasonally dependent. Both suspended sediment yields and the extent of delivery peaked over spring months, supplemented by remobilization of sediment stored during summer months in the main catchment channel. The findings of this study suggest much of the suspended sediment exported from small incised upland sub‐catchments (1–2 km2) may be delivered to downstream reaches under average rainfall conditions, which, in conjunction with the findings of previous research supports the potential importance of contributions from these areas to suspended sediment loads in lowland rivers during high flow periods. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

3.
Sediment transport from mountainous to lowland areas is considered one of the most important geomorphological processes. In the present study, variations in transported sediment loads and dissolved loads have been studied over 3 years (2008–2011) for two forested catchments located in the Lesser Himalayan region of India. Seasonal and annual suspended sediment flux was strongly influenced by amounts of rainfall and streamflow. On average, 93% of annual load was produced during the monsoon, of which 62–78% occurred in only five peak events. Sediment production by the degraded forest catchment (Bansigad) was 1.9-fold (suspended sediment load) to 5.9-fold (bedload) higher than the densely forested catchment (Arnigad). The dissolved organic matter potentially influences total dissolved solids in the stream. Heavy rainfall triggers both stream discharge and landslides, which lead to higher bedload transport. Total denudation rates for Arnigad and Bansigad were estimated at 0.68 and 1.02 mm?year?1, respectively.  相似文献   

4.
This paper investigates suspended sediment transport and dynamics of two nested agricultural lowland Mediterranean catchments with a difference of two orders of magnitude in the surface area (i.e., 1 and 264 km2). The effects of the drainage catchment area over the specific suspended sediment yield are assessed by using the nested approach over various timeframes. A detailed analysis of the rainfall–runoff–sediment transport relationships during the 2‐year study period shows that the hydrological and sedimentological responses were extremely variable for both catchments. Very low or no correlations were observed between the rainfall intensity and the selected hydrological variables and sediment loads. However, remarkable or high correlations were obtained between the rainfall intensity and the maximum and average suspended sediment concentrations, indicating that rainfall per unit time has little control on the hydrological response, but that, simultaneously, its high‐erosive power triggers sediment production, increasing the sedimentary response of the catchments. This study also illustrates how sediment is mainly transported during floods, producing predominantly clockwise hysteretic loops. Moreover, the small headwater catchment exerts a reduced (or even negligible) effect over the hydro‐sedimentary response of the larger downstream catchment, caused by the reduced sediment availability in a landscape with an inherent disconnection of the sediment pathways.  相似文献   

5.
《水文科学杂志》2013,58(6):899-915
Abstract

The results are described of 16 years operation of a measuring station for the automatic recording of water discharge, bed load and suspended sediment transport in the Rio Cordon catchment, a small alpine basin (5 km2) located in northeastern Italy. Hillslope erosion processes were investigated by surveying individual sediment sources repeatedly. Annual and seasonal variations of suspended sediment load during the period 1986–2001 are analysed along with their contribution to the total sediment yield. The results show that suspended load accounted for 76% of total load and that most of the suspended sediment transport occurred during two flood events: an extreme summer flash flood in September 1994 (27% of the 16-years total suspended load) and a snowmelt-induced event in May 2001 accompanied by a mud flow which fed the stream with sediments. The role of active sediment source areas is discussed in relation to the changes in flood peak—suspended load trends which became apparent after both the 1994 and the 2001 events.  相似文献   

6.
The dynamics of suspended sediment transport were monitored continuously in a large agricultural catchment in southwest France from January 2007 to March 2009. The objective of this paper is to analyse the temporal variability in suspended sediment transport and yield in that catchment. Analyses were also undertaken to assess the relationships between precipitation, discharge and suspended sediment transport, and to interpret sediment delivery processes using suspended sediment‐discharge hysteresis patterns. During the study period, we analysed 17 flood events, with high resolution suspended sediment data derived from continuous turbidity and automatic sampling. The results revealed strong seasonal, annual and inter‐annual variability in suspended sediment transport. Sediment was strongly transported during spring, when frequent flood events of high magnitude and intensity occurred. Annual sediment transport in 2007 yielded 16 614 tonnes, representing 15 t km?2 (85% of annual load transport during floods for 16% of annual duration), while the 2008 sediment yield was 77 960 tonnes, representing 70 t km?2 (95% of annual load transport during floods for 20% of annual duration). Analysis of the relationships between precipitation, discharge and suspended sediment transport showed that there were significant correlations between total precipitation, peak discharge, total water yield, flood intensity and sediment variables during the flood events, but no relationship with antecedent conditions. Flood events were classified in relation to suspended sediment concentration (SSC)–discharge hysteretic loops, complemented with temporal dynamics of SSC–discharge ranges during rising and falling flow. The hysteretic shapes obtained for all flood events reflected the distribution of probable sediment sources throughout the catchment. Regarding the sediment transport during all flood events, clockwise hysteretic loops represented 68% from river deposited sediments and nearby source areas, anticlockwise 29% from distant source areas, and simultaneity of SSC and discharge 3%. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

7.
An important gap in the management of land erosion in mining-affected areas is the understanding of the entire sediment routing system and the links between sources and storage at the catchment scale. In this study, we examine sediment delivery and its seasonality in the nickel mining-affected Santa Cruz and Pamalabawan catchments in the Philippines. We monitored discharge, suspended sediment concentrations and suspended sediment loads across 13 sub-catchments with contrasting degrees of mining influence from June 2018 to July 2019. First, we show the importance of the size of the area that has been physically disturbed within our sub-catchments, with as little as 10–22% of relative disturbance area being enough to generate four-fold to eight-fold increase in the sediment yield relative to less disturbed and pristine areas. We found that sub-catchments with > 10% disturbance exhibit the highest sediment yields (15.5 ± 44.7 t km−2 d−1) compared with sub-catchments with < 10% disturbance (3.6 ± 17.7 t km−2 d−1) and undisturbed catchments (2.0 ± 5.7 t km−2 d−1). We also show that sediment flushing predominantly occurs in the most disturbed sub-catchments at the onset of the wet season. A small number of flood events transports the bulk of the sediment, with hysteresis effects being most pronounced in disturbed areas. Lastly, we show that floodplain sediment recycling exerts a key control on sediment delivery at both reach and catchment scales, with the relative contribution of floodplain sources to the sediment budget becoming dominant in the latter stages of the wet season- up to 89% of the total sediment export per storm event. This study highlights the importance of both degree of disturbance and sediment pathways in controlling sediment transport in mining-disturbed areas, and that considering the entire sediment routing system including intermediate stores is crucial to optimizing existing and future measures against siltation and potential contamination of trace metals and metalloids downstream of mining areas.  相似文献   

8.
The suspended sediment response of a small catchment subjected to farmland abandonment and subsequent plant recolonization was studied in relation to its hydrological functioning. The analysis of data over a seven‐year period demonstrated that suspended sediment yield was greatly influenced by the occurrence of intense, low‐frequency events. Greater amounts of suspended sediment were exported during spring, when the catchment was hydrologically more active. Rainfall intensity and baseflow at the start of a flood event had a strong influence on the sediment response, suggesting that several hydrological processes were active within the catchment. SSC (suspended sediment concentration)‐Q hysteretic loop analysis at the event scale aided understanding of the sedimentological and hydrological behaviour of the catchment. During the study period the SSC‐Q loops showed a high degree of seasonality and two main patterns strongly related to catchment wetness were distinguished. When the catchment was dry (mainly during summer and the beginning of autumn) the predominant process was infiltration excess runoff over sparsely vegetated areas close to the main channel. Under these conditions, floods exhibited a counter‐clockwise hysteretic loop and were characterized by a small streamflow response, short duration and high SSC. Under wet conditions (mainly during winter and spring), saturation excess runoff was increasingly dominant over vegetated areas. Under these conditions, floods exhibited a clockwise hysteretic loop, and were characterized by a larger streamflow response, longer duration and higher suspended sediment yield. The lower SSC during the falling stage of the hydrograph is likely to be due to dilution effects related to the contribution of clean water resulting from enlargement of the saturated areas, together with an increase in the baseflow discharge. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

9.
The Loess Plateau has been experiencing large‐scale land use and cover changes (LUCCs) over the past 50 years. It is well known about the significant decreasing trend of annual streamflow and sediment load in the catchments in this area. However, how surface run‐off and sediment load behaved in response to LUCC at flood events remained a research question. We investigated 371 flood events from 1963 to 2011 in a typical medium‐sized catchment within the Plateau in order to understand how LUCC affected the surface run‐off generation and sediment load and their behaviours based on the analysis of return periods. The results showed that the mean annual surface run‐off and sediment load from flood events accounted for 49.6% and 91.8% of their mean annual totals. The reduction of surface run‐off and associated sediment yield in floods explained about 85.0% and 89.2% of declines in the total annual streamflow and sediment load, respectively. The occurrences of flood events and peak sediment concentrations greater than 500 kg/m3 showed a significantly downward trend, yet the counterclockwise loop events still dominated the flood event processes in the catchment. The results suggest that LUCC over the past 50 years resulted in significant changes in the water balance components and associated soil erosion and sediment transportation in the catchment. This was achieved mainly by reducing surface run‐off and sediment yield during floods with return period of less than 5 years. Run‐off–sediment load behaviour during the extreme events with greater than 10‐year return periods has not changed. Outcomes from this study are useful in understanding the eco‐hydrological processes and assisting the sustainable catchment management and land use planning on the Loess Plateau, and the methodologies are general and applicable to similar areas worldwide.  相似文献   

10.
A study was carried out on a rural catchment located in northwest Spain to examine the sediment yield from the catchment by measuring suspended sediments during rainfall events. Within the catchment regular surveys were conducted to obtain data on the suspended sediment sources. Important variations in sediment load were detected at event scale (0·3–21·0 Mg); some of these can be explained in terms of event size, antecedent conditions, rainfall distribution and soil surface erosion. To study the variables controlling suspended sediment yield during the events in the catchment, several event and pre‐event variables were calculated for all events. The sediment load is strongly influenced by discharge variables. During the events discharge–suspended sediments were also analysed. When the soil surface was unprotected, the formation of rills and ephemeral gullies on agricultural land at the catchment head was an important source of suspended sediments in the catchment. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

11.
Sediment loads have been measured in six Swiss mountain torrents over several decades. Most of these torrent catchments are situated in the prealpine belt. They have catchment areas of between 0·5 and 1·7 km2. Bedslopes at the measuring sites vary between 5 and 17 per cent, and peak discharges up to 12 m3 s−1 have been recorded. Geophone sensors installed in the Erlenbach stream allow bedload transport activity to be monitored and sediment volumes associated with each flood event to be determined. A detailed analysis of the measurements in this stream results in an empirical equation in which the sediment load per flood event is expressed as a function of the effective runoff volume (discharges above the threshold for bedload motion) and of the normalized peak discharge. For the total of 143 investigated flood events in the Erlenbach stream, the deviation of the predicted from the measured value is within a factor of two for more than two-thirds of all events. A distinction can be made between summer and winter events in analysing the bedload transport events. The summer events, mainly caused by thunderstorms, transport comparatively larger sediment loads than the winter events. For the other investigated streams, the periods of the deposited sediment volume surveys cover in general several flood events. An analysis is performed analogous to that for the Erlenbach stream. The sediment loads show a similar dependency on the two factors effective runoff volume and normalized peak discharge. However, the exponents of these factors in the power law expressions differ from stream to stream. A comparison of the investigated stream shows that some of the variation can be explained by considering the bedslope above the measuring site. The inclusion of a bedslope factor is in agreement with laboratory investigations on bedload transport. © 1997 John Wiley & Sons, Ltd.  相似文献   

12.
One year of instantaneous suspended sediment concentration, C, and instantaneous discharge, Q, data collected at Ngarradj downstream of the Jabiluka mine site indicate that the use of a simple C–Q rating curve is not a reliable method for estimating suspended sediment loads from the Ngarradj catchment. The C–Q data are not only complicated by hysteresis effects within the rising and falling stages of individual events, but also by variable depletion of available suspended sediment through multipeaked runoff events. Parameter values were fitted to an event‐based suspended sediment load–Q relationship as an alternative to the C–Q relationship. Total suspended sediment load and Q data for 10 observed events in the Ngarradj stream catchment were used to fit parameter values to a suspended sediment load–Q relationship, using (a) log–log regression and (b) iterative parameter fitting techniques. A more reliable and statistically significant prediction of suspended sediment load from the Ngarradj catchment is obtained using an event‐based suspended sediment load–Q relationship. Fitting parameters to the event‐based suspended sediment load–Q relationship using iterative techniques better predicts long‐term suspended sediment loads compared with log–log regression techniques. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

13.
In order to understand the differences in the suspended sediment and total dissolved solid (TDS) yield patterns between the glacial and non‐glacial catchments at the headwaters of Urumqi River, northwestern China, water samples were collected from a glacier catchment and an empty cirque catchment within the region, during three melting seasons from 2006 to 2008. These samples were analyzed to estimate suspended sediment and TDS concentrations, fluxes and erosion rates in the two adjoining catchments. There were remarked differences in suspended sediment and TDS yield patterns between the two catchments. Suspended sediment concentrations were controlled mainly by the sediment source, whereas TDS concentrations were primarily related to the hydrologic interaction with soil minerals. Generally, the glacial catchment had much higher suspended sediment and TDS yields, together with higher denudation rates, than the non‐glacial catchment. Overall, glacial catchment was mainly dominated by physical denudation process, whereas the non‐glacial catchment was jointly influenced by physical and chemical denudation processes. The observed differences in material delivery patterns were mainly controlled by the runoff source and the glacial processes. The melting periods of glacier and snow were typically the most important time for the suspended sediment and TDS yields. Meanwhile, episodic precipitation events could generate disproportionately large yields. Subglacial hydrology dynamics, glaciers pluck and grind processes could affect erodibility, and the large quantities of dust stored on the glacier surface provided additional sources for suspended sediment transport in the glacial catchment. These mechanisms imply that, in response to climate change, the catchment behaviour will be modified significantly in this region, in terms of material flux. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

14.
Bank erosion is the main source of suspended sediment (SS) and diffuse total phosphorus (TP) in many lowland catchments. This study compared a physically based sediment routing method (Physical method), which distinguishes between stream bed and bank erosion, with the original sediment routing method (Original method) within the Soil and Water Assessment Tool (SWAT) version 2009, for simulating SS and TP losses from a lowland catchment. A SWAT model was set up for the lowland River Odense catchment in Denmark and calibrated against observed stream flow and phosphate (PO4) loads. On the basis of an initial calibration of hydrological and PO4 parameters, the SWAT model with the Original method (Original model) and the SWAT model with the Physical method (Physical model) were calibrated separately against observed SS and TP loads. The SWAT model simulated daily stream flow well but underestimated PO4 loads. The Physical model simulated daily SS and TP better than the Original model. The simulated contribution of bank erosion to SS in the Physical model (99%) was close to the estimated contribution from in situ erosion measurements (90–94%). Compared with the Original method, the Physical method is not only more conceptually correct but also improves model performance. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

15.
Fine sediment delivery to and storage in stream channel reaches can disrupt aquatic habitats, impact river hydromorphology, and transfer adsorbed nutrients and pollutants from catchment slopes to the fluvial system. This paper presents a modelling tool for simulating the time‐dependent response of the fine sediment system in catchments, using an integrated approach that incorporates both land phase and in‐stream processes of sediment generation, storage and transfer. The performance of the model is demonstrated by applying it to simulate in‐stream suspended sediment concentrations in two lowland catchments in southern England, the Enborne and the Lambourn, which exhibit contrasting hydrological and sediment responses due to differences in substrate permeability. The sediment model performs well in the Enborne catchment, where direct runoff events are frequent and peak suspended sediment concentrations can exceed 600 mg l?1. The general trends in the in‐stream concentrations in the Lambourn catchment are also reproduced by the model, although the observed concentrations are low (rarely exceeding 50 mg l?1) and the background variability in the concentrations is not fully characterized by the model. Direct runoff events are rare in this highly permeable catchment, resulting in a weak coupling between the sediment delivery system and the catchment hydrology. The generic performance of the model is also assessed using a generalized sensitivity analysis based on the parameter bounds identified in the catchment applications. Results indicate that the hydrological parameters contributing to the sediment response include those controlling (1) the partitioning of runoff between surface and soil zone flows and (2) the fractional loss of direct runoff volume prior to channel delivery. The principal sediment processes controlling model behaviour in the simulations are the transport capacity of direct runoff and the in‐stream generation, storage and release of the fine sediment fraction. The in‐stream processes appear to be important in maintaining the suspended sediment concentrations during low flows in the River Enborne and throughout much of the year in the River Lambourn. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

16.
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17.
《国际泥沙研究》2022,37(6):715-728
Rainfall-induced floods may trigger intense sediment transport on erodible catchments, especially on the Loess Plateau in China, which in turn modifies the floods. However, the role of sediment transport in modifying floods has to date remained poorly understood. Concurrently, traditional hydrodynamic models for rainfall-induced floods typically ignore sediment transport, which may lead to inaccurate results for highly erodible catchments. Here, a two-dimensional (2D) coupled shallow water hydro-sediment-morphodynamic (SHSM) model, based on the Finite Volume Method on unstructured meshes and parallel computing, is proposed and applied to simulate rainfall-induced floods in the Zhidan catchment on the Loess Plateau, Shaanxi Province, China. For six historical floods of return periods up to 2 years, the numerical results compare well with observations of discharge hydrographs at the catchment outlet. The computed runoff-sediment yield relation is quantitatively reasonable as compared with other catchments under similar geographical conditions. It is revealed that neglecting sediment transport leads to underestimation of peak discharge of the flood by 14%–45%, whilst its effect on the timing of the peak discharge varies for different flood events. For 18 design floods with return periods of 10–500 years, sediment transport may lead to higher peak discharge by around 9%–15%. The temporal pattern of concentrated rainfall in a short period may lead to a larger exponent value of the power function for the runoff-sediment yield relation. The current finding leads us to propose that incorporating sediment transport in rainfall-induced flood modeling is warranted. The SHSM model is applicable to flood and sediment modeling at the catchment scale in support of risk management and water and soil management.  相似文献   

18.
Distributed erosion models, which simulate the physical processes of water flow and soil erosion, are effective for predicting soil erosion in forested catchments. Although subsurface flow through multiple pathways is dominant for runoff generation in forested headwater catchments, the process-based erosion model, Geo-spatial interface for Water Erosion Prediction Project(Geo WEPP), does not have an adequate subsurface component for the simulation of hillslope water flow. In the current study, t...  相似文献   

19.
The variability of rainfall-dependent streamflow at catchment scale modulates many ecosystem processes in wet temperate forests. Runoff in small mountain catchments is characterized by a quick response to rainfall pulses which affects biogeochemical fluxes to all downstream systems. In wet-temperate climates, water erosion is the most important natural factor driving downstream soil and nutrient losses from upland ecosystems. Most hydrochemical studies have focused on water flux measurements at hourly scales, along with weekly or monthly samples for water chemistry. Here, we assessed how water and element flows from broad-leaved, evergreen forested catchments in southwestern South America, are influenced by different successional stages, quantifying runoff, sediment transport and nutrient fluxes during hourly rainfall events of different intensities. Hydrograph comparisons among different successional stages indicated that forested catchments differed in their responses to high intensity rainfall, with greater runoff in areas covered by secondary forests (SF), compared to old-growth forest cover (OG) and dense scrub vegetation (CH). Further, throughfall water was greatly nutrient enriched for all forest types. Suspended sediment loads varied between successional stages. SF catchments exported 455 kg of sediments per ha, followed by OG with 91 kg/ha and CH with 14 kg/ha, corresponding to 11 rainfall events measured from December 2013 to April 2014. Total nitrogen (TN) and phosphorus (TP) concentrations in stream water also varied with rainfall intensity. In seven rainfall events sampled during the study period, CH catchments exported less nutrients (46 kg/ha TN and 7 kg/ha TP) than SF catchments (718 kg/ha TN and 107 kg/ha TP), while OG catchments exported intermediate sediment loads (201 kg/ha TN and 23 kg/ha TP). Further, we found significant effects of successional stage attributes (vegetation structure and soil physical properties) and catchment morphometry on runoff and sediment concentrations, and greater nutrients retention in OG and CH catchments. We conclude that in these southern hemisphere, broad-leaved evergreen temperate forests, hydrological processes are driven by multiple interacting phenomena, including climate, vegetation, soils, topography, and disturbance history.  相似文献   

20.
An integrated field and modelling study was carried out on the 35‐ha La Reina catchment, Chile, to test the hypothesis that the effect of forest cover on flood peaks becomes less important as the size of the hydrological event increases. Meteorological and discharge data were measured at the catchment before and after the pine plantation that covered 80% of the catchment area was logged. Analysis of the measured response of the catchment provides support for the hypothesis but is not conclusive. Therefore, modelling of the catchment using 1000 years of generated rainfall data representative of the current conditions was carried out for the forested and logged states. The simulations show that the absolute difference in discharge between the two cases remains approximately constant as the discharge increases: thus as a percentage of discharge it decreases. This relative convergence appears to become significant at return periods of greater than approximately 10 years. Tests with different hypothetical soil depths for the forested and logged catchments show an absolute convergence in discharge between the two cases for shallow soils and no convergence for deep soils. Sediment transport simulations show that forest cover provides a clear benefit in protecting the soil from erosion. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

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