The impact of sowing density of small grains on rill and ephemeral gully erosion in concentrated flow zones

2002 ◽  
Vol 64 (3-4) ◽  
pp. 189-201 ◽  
Author(s):  
G Gyssels ◽  
J Poesen ◽  
J Nachtergaele ◽  
G Govers
Keyword(s):  
Gully Erosion ◽  
Concentrated Flow ◽  
Ephemeral Gully ◽  
Small Grains ◽  
The Impact

Ephemeral Gully Erosion Advancements within the AnnAGNPS Watershed Simulation Model

2020 ◽  
Author(s):  
Ronald Bingner ◽  
Robert Wells ◽  
Henrique Momm
Keyword(s):  
Conservation Management ◽  
Gully Erosion ◽  
Conservation Practices ◽  
Rill Erosion ◽  
Management Planning ◽  
Channel Erosion ◽  
Ephemeral Gully ◽  
Ephemeral Gullies ◽  
The Impact ◽  
The U.S

<p>Concentrated runoff increases erosion and moves fine sediment and associated agrichemicals from upland areas to stream channels. Ephemeral gully erosion on croplands in the U.S. may contribute more of the sediment delivered to the edge of the field then from sheet and rill erosion. Typically, conservation practices developed for sheet and rill erosion are also expected to treat ephemeral gully erosion, but science and technology are needed to account for the separate benefits and effects of practices on each of the various sediment sources.</p><p>Watershed modeling technology has been widely developed to aid in evaluating conservation practices implemented as part of a management plan, but typically lacks the capability to identify how a source, such as sheet and rill erosion, ephemeral gully erosion, or channel erosion, is specifically controlled by a practice or integrated practices. The U.S. Department of Agriculture’s Annualized Agricultural Non-Point Source pollutant loading model, AnnAGNPS, has been developed to determine the effects of conservation management plans on erosion and provide sediment tracking from all sources within the watershed, including sheet and rill, ephemeral gully, and channel erosion. </p><p>This study describes the ephemeral gully erosion capabilities within the AnnAGNPS model and discusses research needs to further improve these components for integrated conservation management planning.  Conservation management planning by agencies within the U.S. and by international organizations requires a systematic approach when determining the extent of ephemeral gully erosion impacts on a field, watershed, or national basis, and/or to predict recurring or new locations of ephemeral gullies prior to their development.  This technology provides the capability to separate the impact of ephemeral gullies on erosion from other sources and then evaluate the impact of targeted practices to control erosion at the source and subsequent downstream resources.</p>

scholarly journals Nautilus multi-grain model: Importance of cosmic-ray-induced desorption in determining the chemical abundances in the ISM

2018 ◽  
Vol 615 ◽  
pp. A20 ◽  
Author(s):  
Wasim Iqbal ◽  
Valentine Wakelam
Keyword(s):  
Grain Size ◽  
Surface Temperature ◽  
Gas Phase ◽  
Numerical Models ◽  
Cosmic Ray ◽  
Grain Sizes ◽  
Small Grains ◽  
Grain Model ◽  
Grain Surface ◽  
The Impact

Context. Species abundances in the interstellar medium (ISM) strongly depend on the chemistry occurring at the surfaces of the dust grains. To describe the complexity of the chemistry, various numerical models have been constructed. In most of these models, the grains are described by a single size of 0.1 μm. Aims. We study the impact on the abundances of many species observed in the cold cores by considering several grain sizes in the Nautilus multi-grain model. Methods. We used grain sizes with radii in the range of 0.005 μm to 0.25 μm. We sampled this range in many bins. We used the previously published, MRN and WD grain size distributions to calculate the number density of grains in each bin. Other parameters such as the grain surface temperature or the cosmic-ray-induced desorption rates also vary with grain sizes. Results. We present the abundances of various molecules in the gas phase and also on the dust surface at different time intervals during the simulation. We present a comparative study of results obtained using the single grain and the multi-grain models. We also compare our results with the observed abundances in TMC-1 and L134N clouds. Conclusions. We show that the grain size, the grain size dependent surface temperature and the peak surface temperature induced by cosmic ray collisions, play key roles in determining the ice and the gas phase abundances of various molecules. We also show that the differences between the MRN and the WD models are crucial for better fitting the observed abundances in different regions in the ISM. We show that the small grains play a very important role in the enrichment of the gas phase with the species which are mainly formed on the grain surface, as non-thermal desorption induced by collisions of cosmic ray particles is very efficient on the small grains.

Impacts of tillage practices on ephemeral gully erosion in a dry-hot valley region in southwestern China

2019 ◽  
Vol 187 ◽  
pp. 72-84 ◽  
Author(s):  
Li Rong ◽  
Xingwu Duan ◽  
Guangli Zhang ◽  
Zhijia Gu ◽  
Detai Feng
Keyword(s):  
Gully Erosion ◽  
Southwestern China ◽  
Tillage Practices ◽  
Ephemeral Gully

A field investigation on ephemeral gully erosion processes under different upslope inflow and sediment conditions

2019 ◽  
Vol 572 ◽  
pp. 517-527 ◽  
Author(s):  
Tongjia Wu ◽  
Chengzhong Pan ◽  
Changjia Li ◽  
Mingjie Luo ◽  
Xiaoyu Wang
Keyword(s):  
Field Investigation ◽  
Gully Erosion ◽  
Erosion Processes ◽  
Ephemeral Gully

An experimental study on dynamic processes of ephemeral gully erosion in loess landscapes

Geomorphology ◽  
2011 ◽  
Vol 125 (1) ◽  
pp. 203-213 ◽  
Author(s):  
J.G. Gong ◽  
Y.W. Jia ◽  
Z.H. Zhou ◽  
Y. Wang ◽  
W.L. Wang ◽  
...  
Keyword(s):  
Experimental Study ◽  
Gully Erosion ◽  
Dynamic Processes ◽  
Ephemeral Gully

Analysis and assessment of ephemeral gully erosion in wide areas of Navarre (Spain) from routinely obtained ortophotographs

2020 ◽  
Author(s):  
Youssef Chahor ◽  
Javier Casalí ◽  
Rafae Giménez
Keyword(s):  
Management Practices ◽  
Sudden Change ◽  
Low Frequency ◽  
Direct Methods ◽  
Gully Erosion ◽  
Aerial Photographs ◽  
Large Area ◽  
Small Watersheds ◽  
Ephemeral Gully ◽  
Ephemeral Gullies

<p>Ephemeral gullies (EG) are linear erosion features located in swales where runoff concentrates during or immediately after rainfall events. EG are temporary because they are easily filled by conventional machinery and cause important soil losses in cultivated areas. Casalí et al. (1999) distinguished three types of EG: “classical”, formed by concentrated runoff flows within the same field where runoff started; “drainage”, created by concentrated flows draining areas upstream from the field; “discontinuity”, found in places where management practices create a sudden change in slope. There is still a great lack of knowledge about the true extent and importance of this EG. In this sense, the information obtained from aerial photographs can be of great value. The main objective of this work is to evaluate the possibility of making an exhaustive characterization of the space-time evolution of ephemeral gullies in a relatively large area from color aerial photographs. The effect of precipitation on the EG will be also analyzed.</p><p>The 570 ha study area is almost completely cultivated with winter cereals and located in the Pitillas district (Navarre). Climate is Continental Mediterranean (on average 550  mm yr<sup>-1</sup>). Soil (upper horizons) are loam–silty loam in texture.</p><p>EG within cultivated fields were located, classified and digitized using GIS interfaces over seven colour orthophotos (1:5000 with 0.5mx0.5m resolution) taken between 2003 and 2014. Gully length was determined after locating EG down and upstream ends. EG drainage areas and slopes were determined using a 2 m resolution DEM.</p><p>To determine EG volumes, an empirical power model for the study area defining the relationship between EG lengths and volumes was first obtained from previous field measurement, and then used for the EG lengths from this study. The corresponding erosion rates were also calculated.</p><p>57 small watersheds affected by EGs were identified, being 39 of them classified as drainage EGs, and the remaining 18 EGs as classic. 70% of the small watersheds were affected by EG only once. In remaining watersheds EG reappeared from twice to seven times. Therefore, it seems that the repeatability is not as high as thought.</p><p>The average erosion rate in classical EG is about 1.1 Kg m<sup>-2</sup> year<sup>-1</sup>. Previous assessments using accurate direct methods reported an average value of 0.8 Kg m<sup>-2</sup> year<sup>-1</sup> for very similar watersheds in the same area. Although it is not a conclusive proof, this findings indicate that both methods provide similar results.</p><p>A very high correlation (r<sup>2</sup>= 0.84) has been found between the length of the gullies formed in the study area and the total annual precipitation. It would follow that EG erosion would also be controlled by the overall amount of rainfall also in Mediterranean climates, and not only by high intensity-low frequency events.</p><p><strong>References</strong></p><ol><li>Casalí, J. J. López, J. V. Giráldez, 1999. Ephemeral gully erosion in Southern Navarra (Spain). CATENA 36: 65-84.</li> </ol>

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