Annual Sediment Delivery Research Articles

近70年来不同地貌和植被类型区水沙特征演变及其对生态恢复的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 近70年来不同地貌和植被类型区水沙特征演变及其对生态恢复的响应 DOI: 10.5846/stxb202012103146 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目(41877083, 41440012, 41230852) Hydrologic and sediment responses to ecological restoration in different geomorphological and vegetation type areas in past 70 years Author: Affiliation: Fund Project: The National Natural Science Foundation of China (General Program, Key Program, Major Research Plan) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:黄土高原水土流失治理和退耕还林(草)等生态环境建设,对不同植被类型区和治理度下的水沙过程均产生了深刻的影响。以北洛河流域为例,基于1952-2019年实测水文数据,采用水文统计法,对比分析了上、中、下游等不同地貌和植被类型区生态恢复对水沙数量、径流调节、影响因素贡献等的影响及其差异。结果显示:(1)上、中、下游年均径流深分别为30、23、21 mm,产沙量为0.6、0.05、-0.02亿t。中游年均产流量占流域总水量的51%,上游年均产沙量占流域总沙量的90%以上。(2)上、中、下游径流深极显著减少,减少率分别为-0.28、-0.16、-0.43 mm/a;上游产沙量以0.02亿t/a速度极显著降低,中、下游产沙量不显著减少。(3)上、中、下游的削洪、补枯程度逐年代增加,与20世纪60年代比,21世纪10年代洪水期流量(Q5)分别减少了63%、45%、60%,上游枯水期流量(Q95)增加了68%,中游20世纪80年代枯水期开始产流。(4)与20世纪60年代比,上、中、下游21世纪10年代人类活动对产流量减少的贡献率分别为94.7%、26.7%、60.7%,而对产沙量减少的贡献率均大于85%。结果表明,植被盖度低但生态恢复程度大的上游,主要受人类活动因素影响,产流产沙量极显著减少,径流调节程度较高,产沙量越集中于暴雨过程;植被覆盖程度高但生态恢复程度小的中游,主要受气候因素主导,产流量明显减少,产沙量微弱降低,径流调节程度弱。水沙数量变化大小及径流调节功能程度,不仅受植被恢复程度的影响,还决定于区域植被盖度的大小。研究可为理解黄土高原的生态水文过程提供理论支撑。 Abstract:The purpose of this study was to reveal the effects of ecological environment construction such as soil and water conservation and the Grain for Green Program on hydrological processes in different vegetation type areas on the Loess Plateau. This work took the Beiluo River Basin as an example to investigate the hydrological responses and the variety in the regions with various landforms and vegetation zones in the basin. The results showed that: (1) the average annual streamflow depth in the upper, middle, and lower reaches was 30, 23, and 21 mm, respectively, while the correspondingly average annual sediment was 60, 5, and -2 million tons from 1952 to 2019. The average annual streamflow volume of the middle reaches accounted for 51% of the total volume in the whole basin. However, the average annual sediment delivery in the upper reaches accounted for over 90% of the total sediment in the basin. (2) All the streamflow depths in the three regions showed a significantly decreasing trend with the changing rates of -0.28, -0.16 and -0.43 mm/a in past 70 years, respectively. While the sediment delivery of the upper reaches demonstrated a significant downward trend at a rate of 2 million t/a, and in the middle and lower reaches it was only a slight reduction. (3) The function of runoff regulation was more and more enhanced with the time. Compared with 1960s, the high flow (Q5) decreased by 63%, 45% and 60% in the 2010s, respectively, in the three regions. While the low flow (Q95) increased by 68% in the upper reaches, and in the middle reaches it began to increase in 1980s. (4) Compared with 1960s, human activities contributed the reduction of streamflow by 94.7%, 26.7%, and 60.7% in 2010s, respectively, which dominated the reduction of sediment delivery of over 85% in the three regions. The results suggest that in the upper reaches with low vegetation cover but high speedy conservation measures, human activities dominated the significant reduction of streamflow and sediment, with runoff highly regulated and soil erosion more and more concentrated in several rainstorms. In the middle reaches, which had high vegetation cover but low speedy conservation measures, climate change dominated the hydrology with the runoff evidently decreased and slightly regulated. It implied that the responses of streamflow and sediment not only controlled by vegetation cover but also the restoration speed. It was expected to be helpful in understanding the ecohydrological processes in the Loess Plateau. 参考文献 相似文献 引证文献

Changing River Discharge and Suspended Sediment Transport to the Georgia Bight: Implications to Saltmarsh Sustainability

Windom, H.L. and Palmer, J.D., 2022. Changing river discharge and suspended sediment transport to the Georgia Bight: Implications to saltmarsh sustainability. Journal of Coastal Research, 38(3), 512–522. Coconut Creek (Florida), ISSN 0749-0208. Suspended sediment delivered in river discharge to the Georgia Bight (the coastal-shelf area of the SE U.S. Atlantic coasts of Georgia and South Carolina) provides a continuous supply of fine grain sediments to support coastal saltmarshes. Archived data on discharge and suspended sediment loads for Piedmont and Coastal Plain rivers collected over eight to nine decades were used to estimate the present rate of sediment discharge to the Bight to be about 1 × 106 metric tons annually. The data used in this assessment are for the period after major reservoir/dam construction and other streamflow diversions occurring during the 1950s–1970s, which had a major effect on sediment yields of SE Atlantic watersheds. The estimated annual sediment delivery is about two-thirds of that needed to maintain vertical saltmarsh stability as sea level rises at the present regional rate of 3.3 mm/y. The observed 2% per decade decreasing trend in river discharge to the Bight, related to rapid population and temperature rise since ca. 1960, and the continual depletion of sediment stored in river floodplains below dams, suggests that the fine sediment supply to the coast will continue to decline.

Sediment Mobilization by Hurricane‐Driven Shallow Landsliding in a Wet Subtropical Watershed

AbstractThe role of individual tropical cyclones in mobilizing sediment by shallow landsliding has been studied widely in islands of the Pacific but hardly within the Insular Caribbean. An opportunity to conduct such a study materialized in 2017 when Hurricane María provoked over 70,000 landslides on the island of Puerto Rico. Through aerial photo interpretation and high‐resolution digital elevation models, this study provides an estimate of the net mobilization and delivery of sediment by shallow landslides in a wet subtropical and actively cultivated 43.8 km2 watershed. Landslide mobilization and delivery are contextualized here in terms of other active sources of sediment and annual sediment delivery. Maximum hourly and 24‐h average rain intensities within the study watershed during Hurricane María were 68 and 10.2 mm h−1, respectively, and these represent intensities with local recurrence intervals of less than 10 years. However, these rain intensities were sufficient to trigger 2,318 landslides that mobilized 230,510–436,330 Megagrams of sediment, an amount that is much greater than surface erosion contributions and represents the equivalent of 0.5–3.6 years of annual watershed‐scale sediment delivery. The high susceptibility to landsliding in this region of Puerto Rico is linked to the abundance of roads (∼21 km km−2), particularly those crisscrossing terrain with slopes ranging from 30° to 60°. Only 15% of these roads are within actively cultivated areas. The remaining roads represent the support infrastructure of abandoned coffee farms that still appear to be inducing a legacy of much geomorphological and watershed management relevance.

Analysing the land-use change effects on soil erosion and sediment in the North of Iran; a case study: Talar watershed

This research aims at predicting the future land-use and examining the effects of the land-use changes on the present and future soil erosion and sediment delivery. Then, Land Change Modeler (LCM) and Geo-spatial Water Erosion Prediction Project (GeoWEPP) were applied. Annual suspended sediment derived from sediment rating curves in Talar Watershed, Iran was used to evaluate the GeoWEPP. The predicted sediment load values of 2016 by GeoWEPP in the likely zone of 0.5 for Shirgah-Talar and Valikbon hydrometric stations were achieved respectively as 756094 and 62082.8 ton. Moreover, the mean annual sediment delivery per unit area of 2000, 2010, 2016 and 2030 were calculated respectively as 37.5, 43, 49.4 and 53.2 (t/ha.yr). The reason for the acquired incremental trend of the soil loss and sediment delivery was the land-use change. The results proved the acceptable performance of LCM combined by GeoWEPP to predict the nearby land-use and related sediment delivery.

Application of sediment rating curves to evaluate efficiency of EPM and MPSIAC using RS and GIS

Erosion potential method (EPM) and Modified Pacific Southwest Interagency Committee (MPSIAC) are two empirical models for estimating soil erosion and sediment delivery. These models use a relatively simple formulation, but they are still applied in various areas with different environmental conditions. However, evaluation of their efficiency is challenging. Accordingly, the main purpose of this study is investigating the performance of EPM and MPSIAC in estimating soil erosion and sediment yield using sediment rating curve (SRC) methods. Talar watershed in Iran was selected as the study area and suspended sediment load (SSL) of two Shirgah–Talar and Valikbon stations were used to assess the output of the models. Remote sensing and geographic information system were utilized in implementing the models. The estimated sediment yield values by the models were evaluated using the results of least square error regression and quantile regression (QR) SRC methods. Then, sediment yield values were obtained from 20-year discharge data (1992–2011). Despite the high uncertainty of QR results, the annual sediment delivery values of the models were achieved in an acceptable range. The most likely (with a probability of 0.5) average annual SSL values were between 713 × 103 and 840 × 103 ton for Shirgah–Talar station. Those values for Valikbon station were between 3142 × 101 and 3702 × 101. Moreover, the estimated average sediment yield in Shirgah–Talar station using MPSIAC and EPM were 591392 and 514054 ton/year, respectively. Those values for Valikbon station were 51881 and 27449 ton/year. Then, the results proved the better performance of MPSIAC in estimating SSL in the study area compared with EPM.

Sediment delivery ratio in a small semi-arid watershed under conditions of low connectivity

The semi-arid region in the northeast of Brazil is characterised by rains of high intensity and short duration, with the processes of erosion being aggravated by an inappropriate land-use model. In this region, the lack of measured data for runoff and sediment yield increases the need to apply hydro-sedimentological models in estimating erosion, requiring knowledge of the actual sediment delivery ratio for the region. The aim of this study therefore, was to map soil erosion, making use of the Universal Soil Loss Equation (USLE), in the Iguatu Experimental Watershed (IEW). The mean annual sediment delivery ratio (SDR), and the SDR for individual events, was calculated from hydro-sedimentological measurements, contributing to an understanding of the processes of sediment propagation in the Brazilian semi-arid region, allowing identification of areas susceptible to water erosion. The IEW has an area of 16.74 km2 and is equipped with sensors for the continuous measurement of rainfall, flow and sediment yield. The mean annual SDR for the IEW was 0.37%. The SDR for individual rainfall events ranged from 0.08 to 1.67%, with an average of 0.68%. Among the main variables that influence the SDR for individual events is the magnitude of rainfall depth and antecedent soil moisture that can be better represented by the total antecedent precipitation of the previous 15 days. According to maps of soil loss, only 6.27% of the watershed presented losses beyond tolerable limits.

Changes in the areal extents of the Athabasca River, Birch River, and Cree Creek Deltas, 1950–2014, Peace–Athabasca Delta, Canada

Deltas form where riverborne sediment accumulates at the interface of river mouths and their receiving water bodies. Their areal extent is determined by the net effect of processes that increase their extent, such as sediment accumulation, and processes that decrease their extent, such as erosion and subsidence. Through sequential mapping and construction of river discharge and sediment histories, this study examined changes in the subaerial extents of the Cree Creek and Athabasca River Deltas (both on the Athabasca River system) and the Birch River Delta in northern Canada over the period 1950–2014. The purpose of the study was to determine how, when, and why the deltas changed in areal extent. Temporal growth patterns were similar across the Athabasca and Birch River systems indicative of a climatic signal. Little or no areal growth occurred from 1950 to 1968; moderate growth occurred between 1968 and the early to mid-1980s; and rapid growth occurred between 1992 and 2012. Factors that affected delta progradation included dredging, sediment supply, isostatic drowning, delta front bathymetry, sediment capture efficiency, and storms. In relation to sediment delivered, areal growth rates were lowest in the Athabasca Delta, intermediate in the Birch Delta, and highest in the Cree Creek Delta. Annual sediment delivery is increasing in the Cree Creek Delta; there were no significant trends in annual sediment delivery in the Birch and Athabasca Deltas. There was a lag of up to several years between sediment delivery events and progradation. Periods of delta progradation were associated with low water levels of the receiving basins. Predicted climate-change driven declines in river discharge and lake levels may accelerate delta progradation in the region. In the changing ecosystems of northeastern Alberta, inadequate monitoring of vegetation, landforms, and sediment regimes hampers the elucidation of the nature, rate, and causality of ecosystem changes.

Estimation of historic flows and sediment loads to San Francisco Bay, 1849–2011

Summary River flow and sediment transport in estuaries influence morphological development over decadal and century time scales, but hydrological and sedimentological records are typically too short to adequately characterize long-term trends. In this study, we recover archival records and apply a rating curve approach to develop the first instrumental estimates of daily delta inflow and sediment loads to San Francisco Bay (1849–1929). The total sediment load is constrained using sedimentation/erosion estimated from bathymetric survey data to produce continuous daily sediment transport estimates from 1849 to 1955, the time period prior to sediment load measurements. We estimate that ∼55% (45–75%) of the ∼1500 ± 400 million tons (Mt) of sediment delivered to the estuary between 1849 and 2011 was the result of anthropogenic alteration in the watershed that increased sediment supply. Also, the seasonal timing of sediment flux events has shifted because significant spring-melt floods have decreased, causing estimated springtime transport (April 1st to June 30th) to decrease from ∼25% to ∼15% of the annual total. By contrast, wintertime sediment loads (December 1st to March 31st) have increased from ∼70% to ∼80%. A ∼35% reduction of annual flow since the 19th century along with decreased sediment supply has resulted in a ∼50% reduction in annual sediment delivery. The methods developed in this study can be applied to other systems for which unanalyzed historic data exist.

Sediment delivery from bare and graveled forest road stream crossing approaches in the Virginia Piedmont

Forest road stream crossing approaches, or the section of road immediately adjacent to the stream crossing, represent primary sources and nearly direct pathways for sediment delivery to stream channels. This research quantified sediment delivery rates associated with reopening abandoned legacy road stream crossing approaches and evaluated the effectiveness of gravel surfacing of the entire running surface in reducing sediment delivery at stream crossings in the Virginia Piedmont. Sediment delivery rates from five regraded (bare) legacy road approaches were compared to those from four completely graveled road approaches. Repeated measurements of road derived sediment trapped by silt fences were used to quantify sediment delivery rates from the road approaches for one year (Aug. 5, 2011–Aug. 5, 2012). Annual sediment delivery rates from the bare approaches were 7.5 times higher than those of the gravel approaches. Sediment delivery rates ranged from 34 to 287Mgha−1year−1 for the bare approaches and from 10 to 16Mgha−1year−1 for the graveled approaches. The highest sediment delivery rates were associated inadequate road surface cover and insufficient water control structures. These findings show that reopened legacy roads and associated stream crossing approaches can deliver significant quantities of sediment if roads are not adequately closed or maintained and that corrective best management practices (BMPs), such as gravel and appropriate spacing of water control structures, can reduce sediment delivery to streams.

Monsoon sedimentation on the ‘abandoned’ tide-influenced Ganges–Brahmaputra delta plain

Annual sediment delivery by the Ganges and Brahmaputra rivers to the Bengal margin has kept pace with sea level rise since the mid Holocene, sustaining subaerial growth of the delta. However, the Sundarbans region of the tidal delta is disconnected from major distributary sources of sediment and is often thought to be sediment starved, eroding, and susceptible to the meter of sea level rise predicted for the 21st century. Despite these assumptions, direct sedimentation measurements on the tidal delta plain reveal widespread mean annualized accretion rates of ∼1.1 cm yr−1, although heterogeneous depositional patterns indicate that topography and internal creek networks influence local sediment distribution. Short-lived radioisotope inventories (7Be: t1/2 = 53.3 days) measured on the freshly accumulated sediments indicate that about ½ of the mass deposited on the lower delta was sourced directly from the seasonal flood pulse of the river; the remaining ½ is derived from older (≥1 yr) reworked sediments. Net sedimentation on this part of the delta traps ∼10% of annual Ganges–Brahmaputra sediment load, with accretion rates roughly equivalent to the mean regional rate of relative sea-level rise (RSLR) of ∼1.0 cm yr−1. If these sedimentation rates are representative of longer-term trends and subsidence rates remain stable over the next century, the lower delta plain may continue to maintain its elevation and stability despite documented mangrove retreat around its seaward edges.

A quantitative study of sediment delivery and stream pollution from different forest road types

AbstractThe objective of this paper is to quantify, and enable the prediction of, sediment delivery and water pollution impacts from a spectrum of forest roads. Ten 100–200 m long sections of forest road were selected to incorporate a wide range of the key physical site factors that are likely to affect the rate of sediment generation. Each road section was permanently instrumented for 1 year to measure rainfall and runoff continuously. Suspended load, bedload, and traffic were integrated measurements over 2‐ to 3‐week site‐service intervals. Total annual sediment load (normalized for slope) varied about 25‐fold, from 216 mg m−2 per millimetre of rain for a high‐quality gravel surfaced road with minimal traffic to 5373 mg m−2 per millimetre of rain for an unsurfaced road on an erodible subsoil with moderate light‐vehicle traffic. For the seven gravel‐surfaced roads in this study, truck traffic (axles/week) explained 97% of the variation in annual sediment delivery (per unit of rainfall) from the road. Equations are proposed that allow annual sediment delivery rates to be estimated when net rainfall, road slope, road area, and truck traffic are known. Roads produce runoff rapidly and were found to deliver sediment for about the same duration as rainfall is falling, in this study varying between 5 and 10% of the time. The patterns of sediment delivery measured from the experimental roads (frequency, duration, and intensity) in this study are similar to levels that have been shown to alter the composition of in‐stream macroinvertebrate communities in small (e.g. <10 l s−1), clean, mountain streams. However, in larger well‐mixed streams (e.g. >500 l s−1), dilution is sufficient to prevent concentrations reaching critical levels that are likely to result in biological impacts. Copyright © 2006 John Wiley & Sons, Ltd.

Runoff and sediment generation on bench-terraced hillsides: measurements and up-scaling of a field-based model

Despite widespread bench-terracing, stream sediment yields from agricultural hillsides in upland West Java remain high. We studied the causes of this lack of effect by combining measurements at different spatial scales using an erosion process model. Event runoff and sediment yield from two 4-ha terraced hillside subcatchments were measured and field surveys of land use, bench-terrace geometry and storage of sediment in the drainage network were conducted for two consecutive years. Runoff was 3·0–3·9% of rainfall and sediment yield was 11–30 t ha−1 yr−1 for different years, subcatchments and calculation techniques. Sediment storage changes in the subcatchment drainage network were less than 2 t ha−1, whereas an additional 0·3–1·5 t ha−1 was stored in the gully between the subcatchment flumes and the main stream. This suggests mean annual sediment delivery ratios of 86–125%, or 80–104% if this additional storage is included. The Terrace Erosion and Sediment Transport (TEST) model developed and validated for the studied environment was parameterized using erosion plot studies, land use surveys and digital terrain analysis to simulate runoff and sediment generation on the terraced hillsides. This resulted in over-estimates of runoff and under-estimates of runoff sediment concentration. Relatively poor model performance was attributed to sample bias in the six erosion plots used for model calibration and unaccounted covariance between important terrain attributes such as slope, infiltration capacity, soil conservation works and vegetation cover. Copyright © 2005 John Wiley & Sons, Ltd.

Rill erosion on cultivated hillslopes during two extreme rainfall events in Normandy, France

In the Normandy region of France, two extreme runoff events took place during winter of 1999 and spring of 2000 that caused flooding and considerable on-site as well as off-site damages. After each event, erosion damage was mapped on an experimental cultivated catchment (94 ha). The location and extent of rill, ephemeral gullies and deposits were measured. For each field, information on land use and soil surface characteristics were also collected. Since 1991, when experimental work and survey campaigns were initiated on this catchment, interrill erosion dominated over rill or ephemeral gully erosion. Our objective was to link information on topography, soil surface characteristics, and land use with intensity and type of erosion that developed. Erosion features that were most related to topographic attributes and hence less affected by seasonal variations were ephemeral gullies and some predefined deposit types. Topographic attributes alone were not sufficient to determine development of rill erosion, due to seasonal differences in vegetative cover. At the catchment scale, total erosion varied from 10 t/ha in December with 93% of the catchment area with vegetation cover ≤20%; to 1.5 t/ha in May, with 73% of the catchment area with vegetation cover >60%. The relative importance of ephemeral gully erosion out of total linear erosion varied from ca. 24% for the rainfall events of December to more than ca. 83% for the rainfall events of May. These results also highlight the fact that average annual sediment delivery as well as the relative importance of different erosion forms at the catchment scale cannot be generalised. Erosion prediction and erosion assessment risks are strongly dependent on catchment land use, morphology and storm characteristics.

Landform Changes Determined Photogrammetrically on Deep Loess Soils

ABSTRACT PHOTOGRAMMETRIC equipment and procedures were modified to take low altitude 15 to 30 m (50 to 100 ft) photographs and measure temporal elevation changes on a hillside transect. Elevations were measured to an accuracy of 0.015 m (0.05 ft) and net soil movement was determined for three time intervals and the overall 15-year period. The net soil displacement was 46, 260 and 605 Mg/ha (20, 116 and 269 t/a), respectively, for the 1969-1974, 1974-1978, and 1978-1984 time intervals. The increase in net soil movement in the more recent periods was apparently related to greater average rainfall erosivity values for May and June which increased from 703 to 950 and finally 1260 MJ-mm/ha-h (41 to 56 and finally 74 hundreds of foot-tonf-inch/acre-hour), respectivley, for the above time intervals. The average annual soil loss values were 9, 65 and 100 Mg/ha/y (4, 29 and 45 t/a/y), respectively, for 969-1974, 1974-1978 and 1978-1984 time intervals and 60 Mg/ha/y (27 t/a/y) for the 1969-1974 period. The 15-year average annual sediment delivery was 24%. Measuring soil loss from cropland with photogrammetric procedures and methods has been successfully accomplished and we believe it is a procedure that should be adopted by scientists studying soil loss and sediment yields.