The Topography Meter: a measurement system applicable for gravity-erosion experiments using a novel 3D surface measuring technique

2020 ◽  
Author(s):  
Xiangzhou Xu ◽  
Feilong Xu Xu ◽  
Wenzhao Guo ◽  
Chao Zhao
Keyword(s):  
Overland Flow ◽  
Target Surface ◽  
Rainfall Simulation ◽  
Video Technology ◽  
The Loess Plateau ◽  
Laser Marking ◽  
Mountainous Regions ◽  
Slide Mass ◽  
3D Surface ◽  
Before And After

<p>Gravity erosion is one of the most remarkable natural hazards in mountainous regions, especially on the Loess Plateau of China. Nevertheless, the measurement of failure mass is very difficult because gravity erosion usually occurs randomly and it combines with hydraulic erosion. Here we present a novel testing technique that could quantitatively measure time-variable gravity erosion on the steep loess slopes. A structured light 3D surface measuring apparatus, the Topography Meter, was designed and manufactured in our laboratory. Dynamic variation of the steep slope relief was monitored under rainfall simulation and the slope deforming process was recorded by a computer video technology. With the help of laser marking, plane figures were vectorially transformed into 3D graphs, thus the shape of target surface was accurately computed. By comparing the slope geometries in the moments before and after the erosion incident on the snapshot images at a particular time, we could obtain the volume of gravity erosion and many other erosion data, including the volume of slide mass, the amount of soil loss eroded by overland flow, etc. A series of calibration tests were conducted and the results showed that the accuracy of this technique was high and sufficient for exploring the mechanism of slope erosion. More than 120 rainfall simulation events were subsequently tested with the apparatus, further confirming its feasibility and reliability.</p>

Biogeochemical Fluxes across Piedmont Slopes of the Jornada Basin

2006 ◽  
Author(s):  
Athol D. Abrahams ◽  
Melissa Neave
Keyword(s):  
Overland Flow ◽  
Rainfall Simulation ◽  
Alluvial Fans ◽  
Basin And Range Province ◽  
Form And Function ◽  
Small Watersheds ◽  
Biogeochemical Fluxes ◽  
Basin Floor ◽  
Jornada Basin ◽  
And Function

This chapter is an overview of recent studies of the movement of water, sediment, and nutrients across a principle piedmont slope, or bajada, of the Jornada Basin. Bajadas are extensive, gently sloping surfaces formed by the coalescence of alluvial fans and are a major landscape component of the basin and range province. Over the past four decades a considerable body of research has elucidated the form and function of alluvial fans (Bull 1977; Blair and McPherson 1994; Harvey 1997), but less attention has been paid to bajadas. In particular, the bajadas most neglected are those where channels converge and diverge at irregular intervals downslope. This type of bajada is found at the base of Summerford Mountain, the northernmost peak of the Doña Ana Mountains on the western edge of the Jornada Basin. For convenience, this bajada is hereafter referred to as the Summerford bajada. The research has involved rainfall simulation experiments on small plots, monitoring of two small watersheds on this bajada, and computer modeling of the processes operating in these watersheds and over the bajada as a whole. A detailed understanding of the hydrology and hydraulics of overland flow on this bajada requires a numerical model of the rainfall-runoff process. The objective of this chapter is to detail the model and draw conclusions from model simulations about hydrologic transports of sediment and nutrients across this bajada. Because these piedmonts are important surfaces in this desert (chapter 2) an understanding of their hydrologic and biogeochemical dynamics is crucial to understanding landscape dynamics in the basin and throughout arid regions. Summerford Mountain is a steep-sided, rocky inselberg (i.e., isolated mountain) that rises 380 m above the surrounding bajada to an elevation of 1,780 m. The mountain is composed of monzonite porphyry of Oligocene age (Seager et al. 1976) and has a fringing bajada on its northern and eastern sides. This study focuses on the bajada to the east, which extends 2.5 km to the basin floor at an average gradient of 4%.

Changes in Soil Physical Properties due to Cable Yarding and their Hydrologic Implications

1992 ◽  
Vol 7 (2) ◽  
pp. 36-39 ◽  
Author(s):  
Michael D. Purser ◽  
Terrance W. Cundy
Keyword(s):  
Overland Flow ◽  
Water Storage ◽  
Soil Physical Properties ◽  
Cascade Mountains ◽  
Before And After ◽  
Commercial Logging ◽  
Cable Yarding ◽  
Dominant Process ◽  
Ks Values ◽  
Changes In Soil Properties

Abstract This study was performed to measure changes in soil properties due to cable yarding and to estimate the resulting changes in hydrologic response. Soils were sampled before and after a commercial logging operation in the northern Cascade Mountains of Washington. The samples were analyzed for saturated hydraulic conductivity (Ks), moisture release characteristics, and bulk density (BD). Postlogging Ks values ranged from 1.08 to 497 cm/h and were significantly less than prelogging values, which ranged from 10.8 to 623 cm/h. Postlogging bulk densities ranged from 0.34 to 1.13 g/cm³ and were significantly greater than prelogging values, which ranged from 0.10 to 0.95 g/cm³. Because of the high Ks values it was concluded that Horton overland flow is not a dominant process even after disturbance. A 32.7% reduction in available water storage was found due to decreases in noncapillary porosity and surface horizon thickness. From this, increases in saturation overland flow and/or subsurface flow are predicted on skid trails. Overall impacts on the cutting unit however are considered small. West. J. Appl. For. 7(2):36-39.

Scale Effects of Sediment-Related Transport of Phosphorus

1993 ◽  
Vol 28 (3-5) ◽  
pp. 473-481 ◽  
Author(s):  
S. M. Bolton ◽  
T. J. Ward
Keyword(s):  
Total Phosphorus ◽  
Overland Flow ◽  
Sediment Load ◽  
Scale Effects ◽  
Sediment Concentration ◽  
Rainfall Simulation ◽  
Small Rivers ◽  
Phosphorus Transport ◽  
Simulation Experiments ◽  
Stream Type

Sediment and nutrient data from USGS gauged stream sites in New Mexico and from rainfall simulation experiments were compiled and analyzed. Above a suspended sediment concentration of about 500 mg/l, associated concentrations of total phosphorus are highest in overland flow and then progressively decrease from agricultural drains to ephemeral washes to undammed rivers. Within a stream type, sediment-related concentrations of total phosphorus typically differed between larger and smaller basins. Small rivers had higher phosphorus transport per unit of sediment load than larger rivers. Small and medium sized washes had different relationships between phosphorus and sediment than did large and very large washes.

"Partial area contribution" and "Overland flow discontinuity": from humid to arid hillslopes

2020 ◽  
Author(s):  
Hanoch Lavee
Keyword(s):  
Soil Moisture ◽  
Overland Flow ◽  
Infiltration Rate ◽  
Dead Sea ◽  
Livestock Grazing ◽  
Rainfall Simulation ◽  
Arid Areas ◽  
Shallow Subsurface ◽  
Partial Area ◽  
Semi Arid

<p>In humid temperate areas, where infiltration rate and soil moisture are high the hillslopes are draining mainly via shallow subsurface flow. Overland flow is seldom generated on the very low parts of hillslopes when the soil is saturated up to the surface. This spatial pattern is known as “partial area contribution”.</p><p>In contrary, in arid areas, where the soil moisture is hygroscopic most of the time, overland flow is generated not because of soil saturation conditions but only when rainfall intensity is higher than the infiltration rate.  </p><p>Nevertheless, we found a “partial area contribution” pattern in several arid and semi-arid areas due other controlling factors:</p><ol><li>In eastern Sinai, under rainfall simulation experiments on scree slopes, due to high spatial differences in the soil texture, runoff coefficient in the gullies was almost 100% while in the very permeable interfluves runoff wasn’t generated at all. Overland flow was generated, therefore, only in the gullies (Lavee ,1973; Yair & Lavee ,1976).</li> <li>In an instrumented experimental watershed in the Northern Negev, the specific overland flow yield from long plots ,extending from the divide to the slope base (around 60m in length), was consistently lower than the combined specific overland flow yield from the adjacent two short plots (around 30m in length), draining the upper and the lower sections of the hillslope, respectively. This means that the overland flow is discontinuous and at least part of the overland flow that was generated at the upper part of the hillslope infiltrated, in most overland flow events, into the soil, before reaching the slope base. In other words, only the lower part of the hillslope contributes, in most cases, overland flow to the channel. Such overland flow discontinuity is controlled by: 1. The typical short duration of rain showers in arid areas. As more than 80% of the rain showers last for less than 15 minutes, the total flow duration is usually shorter than the concentration time. 2. The spatial distribution of infiltration rate. In this case it was mainly the relatively high infiltration rate in the colluvial cover at the lower part of the hillslopes in part of the study area that absorbed large amount of the water flowing from the upper part of the hillslopes (Lavee, 1982; Yair & Lavee, 1985; Lavee & Yair, 1990).</li> <li>In an experimental project along a climatological transect, running from the Mediterranean climate near Jerusalem to the extreme arid climate near the Dead Sea, the main reason for the overland flow discontinuity, especially in the semi-arid area, was the mosaic pattern of “source patches”, on which overland flow was generated, and “sink patches”, in which at least part of the direct rain and the incoming overland flow infiltrated. This pattern is produced by different processes, mainly via the effect of vegetation, but also due to the effects of micro-topography, big stones, especially if they are partly embedded in the soil, and livestock grazing (Lavee & Poesen, 1991; Lavee et al., 1998; Stavi et al., 2008).</li> </ol>

Land use impacts on soil detachment capacity by overland flow in the Loess Plateau, China

CATENA ◽  
2015 ◽  
Vol 124 ◽  
pp. 9-17 ◽  
Author(s):  
Zhen-Wei Li ◽  
Guang-Hui Zhang ◽  
Ren Geng ◽  
Hao Wang ◽  
X.C. Zhang
Keyword(s):  
Land Use ◽  
Loess Plateau ◽  
Overland Flow ◽  
Land Use Impacts ◽  
The Loess Plateau

scholarly journals Changes in land-use and their impact on erosion rates and overland flow generation in the Maghreb region

2005 ◽  
Vol 17 (2) ◽  
pp. 163-180 ◽  
Author(s):  
C. O.A. Coelho ◽  
A. J.D. Ferreira ◽  
A. Laouina ◽  
A.-K. Boulet ◽  
M. Chaker ◽  
...  
Keyword(s):  
Land Use ◽  
Soil Erosion ◽  
Land Management ◽  
Overland Flow ◽  
Animal Husbandry ◽  
Rainfall Simulation ◽  
Management Systems ◽  
Simulation Experiments ◽  
Erosion Hazard ◽  
Erosion Rates

The ongoing intensification of grazing as well as the replacement of traditional land management systems in the Maghreb has brought to the forefront the fundamental role of land-use in determining soil erosion hazard. This paper reports on erosion rates and soil hydrological characteristics of a variety of land uses in Morocco and Tunisia. The results were obtained through rainfall simulation experiments carried out in the field using a portable simulator, following the design of CERDÀ et al. (1997). Traditional land management systems - typically involving a combination of agriculture, animal husbandry and forestry - produced the least amounts of overland flow and the lowest soil erosion rates. Over-exploitation of these systems apparently has only minor hydrological and erosional impacts. Heavily grazed, degraded "maquis" shrublands, on the other hand, produced considerable amounts of overland flow. At the plot scale of the rainfall simulation experiments (0.24 m2), the corresponding sediment loads are rather insignificant. Nevertheless, slopes where "maquis" shrublands (which generally have very compacted soils) occur upslope from more erodible soils may present a major erosion hazard.

scholarly journals Study on the influence of vegetation change on runoff generation mechanism in the Loess Plateau, China

2020 ◽  
Author(s):  
Xueli Zhang ◽  
Yue Yu ◽  
CaiHong Hu ◽  
Jianhua Ping
Keyword(s):  
Loess Plateau ◽  
Vegetation Change ◽  
Overland Flow ◽  
Yellow River ◽  
Generation Mechanism ◽  
Underlying Surface ◽  
The Yellow River ◽  
Runoff Generation ◽  
The Loess Plateau ◽  
Related Factors

Abstract In recent years, the amount of water and sediment in the Yellow River Basin has dropped drastically. This paper selected 125 rainfall and flood data points from 1965 to 2015, combined hydrological methods and mathematical statistics to analyze the hydrological factors and runoff generation mechanism, and combined the underlying surface conditions of the Gushanchuan Basin. The characteristics of change revealed the temporal and spatial variation characteristics and related factors of the runoff generation mechanism in the basin. The results showed that the Gushanchuan Basin is still dominated by HOF runoff, but the runoff generation mechanism also has changed with changes in the underlying surface, which are reflected in increased runoff components, the reduced proportion of HOF runoff, and the increased proportion of saturation-excess overland flow (SOF) runoff and mixed runoff. We analyzed the variation law of underlying surface in the basin, which indicated that the increase in the forest grass area was the main factor affecting changes in the watershed runoff generation mechanism. This research will enable a deeper understanding of the runoff generation mechanism of the main soil erosion areas in the Loess Plateau, reveal variations in the runoff generation mechanism in the Yellow River.

scholarly journals Rainfall-runoff processes in the Loess Plateau, China: Temporal dynamics of event rainfall-runoff characteristics and diagnostic analysis of runoff generation patterns

2020 ◽  
Author(s):  
Qiang Wu ◽  
Zhaoxi Zhang ◽  
Guodong Zhang ◽  
Shengqi Jian ◽  
Li Zhang ◽  
...  
Keyword(s):  
Loess Plateau ◽  
Time Scale ◽  
Overland Flow ◽  
Yellow River ◽  
Separation Procedure ◽  
Runoff Coefficient ◽  
Rainfall Runoff ◽  
Runoff Generation ◽  
The Loess Plateau

Abstract. The Loess Plateau is the most erosion-prone area in China, while under large-scale ecological restoration runoff and sediments continue to decrease. This study examined the runoff generation mechanism at the catchment scale to understand the change in runoff generation. Six baseflow used to separation method were tested and the nonparametric simple smoothing method was seperating base flow. With the event runoff separation procedure, 340 rainfall–runoff events are selected in five typical catchments affected by significant human intervention in the Loess Plateau. Runoff characteristics, such as the event runoff coefficient, time scale, rise time, and peak discharge are studied on monthly and long-term scales. In catchments of Jialuhe, Chabagou and Gushanchuan with poor vegetation runoff response is strongly decided by rainfall intensity and is produced by Horton overland flow (HOF). While the mountainous catchments of Jingle and Zulihe runoff response is controlled by rainfall volume. The relation between runoff event characteristics and rainfall is complicated in Loess Plateau, where rainfall and underlying surface is significantly changing. The monthly of event characteristics is mostly controlled by rainfall characteristics. Long-term runoff coefficient experiences decreasing trend, while time scale trend is increasing. Land use changes lead to increasing catchment wetness display mostly strong reason in event characteristic response. According to our proposed framework for classifying dominant runoff generation patterns considering of hydrograph response time, discharge source, and flow paths, HOF runoff is still the dominant mechanism, but gradually shifts to Dunne overland flow (DOF) and combination runoff. We speculate that the reduction in runoff in the Yellow River is likely to be the dominant runoff mechanism changing.

scholarly journals Water uptake strategies by typical broadleaf and coniferous trees in the Loess Plateau mountain area of northern China

2020 ◽  
Author(s):  
Weiwen Zhao ◽  
Youzhi Han ◽  
Wenjun Liang ◽  
Xi Wei
Keyword(s):  
Loess Plateau ◽  
Water Uptake ◽  
Soil Layer ◽  
Water Source ◽  
Northern China ◽  
Water Sources ◽  
The Loess Plateau ◽  
Mountain Area ◽  
Soil Layers ◽  
Before And After

There are few precipitation events in the Loess Platea area, which may significantly influence water uptake strategies for plant communities, while water source for trees, growing in the Loess Plateau mountain area, are poorly comprehend. We investigated the impacts of precipitation (before and after) on water uptake strategies for typical broadleaf and coniferous trees using hydrogen and oxygen stable isotope techniques in the Loess Plateau mountain area of northern China. Our results indicated that water sources of the two plant species varied before and after rainfall. Robinia pseudoacacia largely absorbed water from 30-40cm (57.8%) soil layers before precipitation and switched its main water source to 20-30cm (58.5%) soil layer after precipitation. Contrary to R.pseudoacacia, Pinus tabuliformis mainly absorbed water from 20-30cm (24.9%) and 10-20cm (21.6%) soil layers before precipitation and changed its dominant water sources to 0-10cm (39.8%) and 10-20cm (44%) soil layer after precipitation. Moreover, the herbaceous of broadleaf plant has the higher complex of the community. On the whole, R.pseudoacacia and P.tabuliformis showed the diverse characteristics of water utilization, which suggests that these two species are suitable for a mixed forest vegetation and our findings provide valuable information for planning long-term ecological afforestation management around the Loess Plateau mountain area of northern China.

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