Analysis of ephemeral gully erosion in small agricultural watersheds in Iowa (USA)

2020 ◽  
Author(s):  
Eduardo Luquin ◽  
Richard M. Cruse ◽  
Karl R. Gesch ◽  
Matthew J. Helmers ◽  
Henrique G. Momm ◽  
...  
Keyword(s):  
Cross Section ◽  
The United States ◽  
Gully Erosion ◽  
Soil Productivity ◽  
Time And Space ◽  
Erosion Rates ◽  
No Till ◽  
Ephemeral Gully ◽  
Ephemeral Gullies ◽  
Over Time

<p>Ephemeral gullies (EG) are linear erosion features located in swales where surface and/or subsurface runoff concentrate during or immediately after rainfall events. As its name states, EGs are temporary because they are easily filled by conventional machinery, but when filled they reform if the area is not appropriately managed. Downstream water quality issues and decreased soil productivity are the main environmental impacts. EGs are frequently identified as (the most) relevant sediment sources in agricultural areas but their dimensions and particular contribution to the total erosion under different temporal, spatial, climate and land use condition is still unknown. Therefore, the objective of this study is to obtain ephemeral gully erosion rates and estimate the main morphological characteristics of the ephemeral gullies (width, length and depth) and their evolution both in relation to time and position on the landscape.</p><p>The studied EGs, B6 with a 0.94 ha watershed and I3 with a 0.95 ha watershed formed in two fields located in the Walnut Creek watershed, Iowa (US). The field-sized watersheds are less than 1.5 Km apart and have similar topography and soils. The cropping system consists of a two-year corn-soybean rotation managed by one farmer using no-till and other standard management practices. EG were measured using close range photogrammetry techniques. In order to achieve a suitable characterization of the EG evolution over time and space, EGs were divided in three sections (bottom, middle and top) of equal length. Photographs were taken at least once in 2013, 2014 and 2018 (a total of five in I3 and three in B6). Cross section profiles along the EG perpendicular to the flow path direction were selected and their width, area and depth were determined from a graphical representation of the cross sections. EG volumes were estimated by the sum of interpolating sequential cross-section areas and multiplying by the distance between them.</p><p>Average EG erosion rates during 2013-2014 were 3.19 Mg ha<sup>-1</sup> year<sup>-1</sup> for B6 and 3.63 Mg ha<sup>-1</sup> year<sup>-1</sup> for I3. Values in agreement with rates estimated by the United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) of 0.49 to 5.18 Mg ha<sup>-1</sup> year<sup>-1 </sup>across the USA and other simulated values of 4.00 ± 1.76 Mg ha<sup>-1</sup> year<sup>-1</sup> for no till systems in the state of Iowa. The current study shows evidences that EG in no till systems may not stabilize after their formation. EG dimensions (depth, width and length, thus volume) varied over time and space during the continuously monitored period. In general, volumes tend to increase in the middle position while depths decrease in the bottom position. When the EG was filled, it reformed again in approximately the same location showing similar dimensions to that which existed prior to filling.</p>

scholarly journals Revealing the spatial shifting pattern of COVID-19 pandemic in the United States

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Di Zhu ◽  
Xinyue Ye ◽  
Steven Manson
Keyword(s):  
United States ◽  
Long Range ◽  
Network Optimization ◽  
Network Modeling ◽  
The United States ◽  
Standard Series ◽  
Time And Space ◽  
Long Range Interactions ◽  
Dynamic Relationships ◽  
Over Time

AbstractWe describe the use of network modeling to capture the shifting spatiotemporal nature of the COVID-19 pandemic. The most common approach to tracking COVID-19 cases over time and space is to examine a series of maps that provide snapshots of the pandemic. A series of snapshots can convey the spatial nature of cases but often rely on subjective interpretation to assess how the pandemic is shifting in severity through time and space. We present a novel application of network optimization to a standard series of snapshots to better reveal how the spatial centres of the pandemic shifted spatially over time in the mainland United States under a mix of interventions. We find a global spatial shifting pattern with stable pandemic centres and both local and long-range interactions. Metrics derived from the daily nature of spatial shifts are introduced to help evaluate the pandemic situation at regional scales. We also highlight the value of reviewing pandemics through local spatial shifts to uncover dynamic relationships among and within regions, such as spillover and concentration among states. This new way of examining the COVID-19 pandemic in terms of network-based spatial shifts offers new story lines in understanding how the pandemic spread in geography.

Tropical rock coasts

2012 ◽  
Vol 37 (2) ◽  
pp. 206-226 ◽  
Author(s):  
Cherith A. Moses
Keyword(s):  
Climate Change ◽  
Temporal Variations ◽  
Future Research ◽  
Published Data ◽  
Time And Space ◽  
Erosion Rates ◽  
The Tropics ◽  
Over Time ◽  
Impacts Of Climate Change

Rock coasts are widespread in the tropics and exhibit particular morphologies that may be specific to their tropical, micro-tidal location. Notches are particularly well developed, often linked to onshore cliffs and fronted by subhorizontal platforms. Through a review of previously published data across the tropics, average cliff face erosion rates are calculated as 2.15 ± 2.62 mm a−1, intertidal erosion rates 3.03 ± 7.50 mm a−1 and subtidal erosion rates 0.96 ± 0.44 mm a−1. Intertidal erosion rates are variable within and across latitudinal ranges: within 10°N and S of the equator average rates are 1.42 ± 1.22 mm a−1; between latitudes of 10°and 20°, 0.88 ± 1.16 mm a−1 and between latitudes of 20°and 30°, 2.04 ± 2.57 mm a−1. A consideration of temporal variations in intertidal erosion rates provides insights into the potential impacts of climate change on the erosion dynamics of rock coasts in the tropics. This paper highlights some of the interactions over time and space between process and measurement that continue to limit our understanding of, and ability to model, the erosion dynamics of tropical rock coasts. It concludes by identifying potentially fruitful areas for future research.

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>

scholarly journals Ephemeral gully erosion from agricultural regions in the Pacific Northwest, USA

2010 ◽  
Vol 42 (1) ◽  
pp. 23-29 ◽  
Author(s):  
Michael Barber ◽  
Robert Mahler
Keyword(s):  
High Resolution ◽  
Soil Erosion ◽  
Pacific Northwest ◽  
Gully Erosion ◽  
Aerial Imagery ◽  
Sediment Delivery ◽  
Ephemeral Gully ◽  
The Pacific ◽  
Ephemeral Gullies ◽  
Agricultural Regions

Ephemeral gully erosion from agricultural regions in the Pacific Northwest, USA Soil erosion continues to be problematic financially and environmentally with the USEPA ranking sediment as one of the top ten pollutants of concern in the USA. One aspect of erosion often overlooked is the role of ephemeral gullies in terms of quantity of sediment produced and amount exported to nearby waterways. Current physically-based and empirical models are inadequate for predicting this type of erosion particularly at the watershed scale. A new methodology for predicting the quantity and location of sediment delivery was developed and tested via a case study. Aerial ephemeral gully erosion rates varied from 33.6 mton/km2 (0.15 U.S. tons/acre) in the Big Bear Creek basin to 88.4 mton/km2 (0.39 U.S. tons/acre) in the Middle Potlatch Creek basin representing 2.3 to 7.7% of the total surface sediment load. This information was used to develop a predictive Erosion Potential Index (EPI) that uses LANDSAT aerial imagery combined with readily available soils information and a digital elevation model to identify the most probably locations of ephemeral gully development. High resolution aerial imagery was used to quantify actual ephemeral gully locations which were then compared to the EPI predicted locations to verify the procedure. High resolution aerial imagery was also used to quantify the amounts of soil erosion from ephemeral gullies in basins of the Potlatch River system.

scholarly journals Measuring ephemeral gully erosion rates and topographical thresholds in an urban watershed using unmanned aerial systems and structure from motion photogrammetric techniques

2018 ◽  
Vol 29 (6) ◽  
pp. 1896-1905 ◽  
Author(s):  
Napoleon Gudino-Elizondo ◽  
Trent W. Biggs ◽  
Carlos Castillo ◽  
Ronald L. Bingner ◽  
Eddy J. Langendoen ◽  
...  
Keyword(s):  
Structure From Motion ◽  
Gully Erosion ◽  
Unmanned Aerial Systems ◽  
Urban Watershed ◽  
Erosion Rates ◽  
Ephemeral Gully ◽  
Aerial Systems

scholarly journals Gully geometry: what are we measuring?

SOIL ◽  
2015 ◽  
Vol 1 (2) ◽  
pp. 509-513 ◽  
Author(s):  
J. Casalí ◽  
R. Giménez ◽  
M. A. Campo-Bescós
Keyword(s):  
Cross Section ◽  
Equivalent Width ◽  
Gully Erosion ◽  
Simple Task ◽  
Equivalent Depth ◽  
Ephemeral Gully ◽  
Measurement Protocol ◽  
Wide Range

Abstract. Much of the research on (ephemeral) gully erosion comprises the determination of the geometry of these eroded channels, especially their width and depth. This is not a simple task due to uncertainty generated by the wide range of variability in gully cross section shapes found in the field. However, in the literature, this uncertainty is not recognized so that no criteria for their measurement are indicated. The aim of this work is to make researchers aware of the ambiguity that arises when characterizing the geometry of an ephemeral gully and similar eroded channels. In addition, a measurement protocol is proposed with the ultimate goal of pooling criteria in future works. It is suggested that the geometry of a gully could be characterized through its mean equivalent width and mean equivalent depth, which, together with its length, define an "equivalent prismatic gully" (EPG). The latter would facilitate the comparison between different gullies.

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>

An Analysis of Fraudulent Qui Tam Actions Over Time in the United States

2007 ◽  
Author(s):  
Karen A. Fitzner ◽  
Charlie Bennett ◽  
June McKoy ◽  
Cara Tigue
Keyword(s):  
United States ◽  
The United States ◽  
Over Time

Forecasting Interconnections in International Housing Markets: Evidence from the Dynamic Model Averaging Approach

2020 ◽  
Vol 42 (1) ◽  
pp. 37-103
Author(s):  
Hardik A. Marfatia
Keyword(s):  
Dynamic Model ◽  
Model Averaging ◽  
Housing Markets ◽  
The United States ◽  
Forecasting Model ◽  
Change Over Time ◽  
The United Kingdom ◽  
Novel Approach ◽  
Dynamic Model Averaging ◽  
Over Time

In this paper, I undertake a novel approach to uncover the forecasting interconnections in the international housing markets. Using a dynamic model averaging framework that allows both the coefficients and the entire forecasting model to dynamically change over time, I uncover the intertwined forecasting relationships in 23 leading international housing markets. The evidence suggests significant forecasting interconnections in these markets. However, no country holds a constant forecasting advantage, including the United States and the United Kingdom, although the U.S. housing market's predictive power has increased over time. Evidence also suggests that allowing the forecasting model to change is more important than allowing the coefficients to change over time.

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