Occurrence Of Gullies Research Articles

Assessment of gully influencing factors and susceptibility using remote sensing-based frequency ratio method in Sunshui River Basin, Southwest China.

Gully erosion is a serious global environmental problem associated with land degradation and ecosystem security. Examining the influencing factors of gullies and determining susceptibility hold significance in environmental sustainability. The study evaluates the spatial distribution, influencing factors, and susceptibility of gullies in the Sunshui River Basin in Sichuan Province, Southwest China. The frequency ratio method supported by satellite images and the gully inventory dataset (1614 gully head points) with different influencing factors were applied to assess the distribution and susceptibility of gullies. Additionally, gully head points were grouped into a training set (70%, 1130 points) and a test set (30%, 484 points). Spatial distribution results indicated that most gullies are located in the middle and upper part of the basin, characterized by moderate elevation (2100-3300m), steep slopes (11.63-27.34°), abandoned farmland, and Cambisols soil, and fewer gullies are located in lower part characterized by lower elevation, gentle slopes, and low vegetation coverage. Land use and land cover influence on susceptibility is significantly greater than other factors with a prediction rate of 33.9, especially farmland abandonment, while the occurrence of gullies is also more often on southwest-orientated slopes. Gully susceptibility highlighted that the study area affected by the very low, low, moderate, high, and very high susceptibilities to these gullies covered an area of about 16%, 23%, 32%, 26%, and 3% of the total basin respectively, which indicates 61% of the study area is susceptible to gully erosion. Moderate to high susceptibility is situated in the upper and middle part, consistent with the spatial distribution of gullies in the basin, and very high susceptibility (3%) is distributed in both the lower and upper parts of the basin. These results have important implications for soil loss control, land planning, and integrated watershed management in the mountainous areas of Southwest China.

Degrees of Risk of Environmental Impacts Arising from Irregular Occupations in the Northern Zone of Manaus - Amazonas

The disordered urban growth in the city of Manaus has had serious consequences for the environment in recent years, especially towards the northern part of the city. It is extremely important to verify the environmental impacts caused by this situation, in order to define the priority areas for planning and recovery actions of the areas. Sixteen areas were identified during the study, which were divided into four quadrants to define their risk levels. The risk levels were I - low, II - medium, III - high and IV - very high. The first criterion for dividing the areas in the quadrants was to identify similar characteristics between them and the second, the proximity of the areas, considering, therefore, the size of the area, as well as the loss of vegetation cover, the state of the soil and the existence and quality of the areas. water resources near the occupied areas. It was found that the presence of streams is a decisive factor to increase the environmental risk of a occupied area, in which anthropic actions intensify natural processes. Another factor considered is related to the degree of erosive processes, therefore, the occurrence of gullies and ravines accounted for the increased risk. After accounting for recorded impacts, quadrant B, located in the Cidade de Deus neighborhood, has a high environmental risk, while quadrants C and D have medium risk. These three quadrants have streams in their areas, however, quadrant A, which has no water body, has a low degree of risk, although three of its four areas have gullies. From this analysis, it is possible to define mitigation and impact containment measures, allowing natural resources to be preserved for the well-being of everyone today and for years to come.

Characteristics of Strata Behavior during Thick Seam Mining by Fully-Mechanized Top Coal Caving in a Loess-Covered Gullied Region

This study systematically investigates the overburden movement and strata behavior at a fully-mechanized top coal caving (FMTCC) face in a thick coal seam in a loess-covered gullied region by field measurement and theoretical analysis. A comparative analysis was performed to examine how the attitude of surface gullies and the structure of overburden affect face support resistance. The characteristics and evolution mechanism of strata behavior during FMTCC under gully slopes in a loess-covered gullied region were discovered through a mechanical analysis of the roof structure and a comparison to the mining of a typical shallow seam under gully slopes. The study found that as the FMTCC face advanced, the strata behavior initiated in the middle part of the face and then continued to both ends, and its intensity was higher in the middle part than in the upper and lower parts. During mining under gullies, the increases in support resistance were generally less than 5% (except for the maximum increases of 7–9%), indicating that the occurrence of gullies on the surface had little influence on the strata behavior at the FMTCC face. Due to the increased burial depth and the number of key strata, the roof at the FMTCC face under gullies formed a stable load-bearing structure called a voussoir beam, which was the key difference from the strata behavior characteristics in the shallow mine under gullies.

Unique chronostratigraphic marker in depositional fan stratigraphy on Mars: Evidence for ca. 1.25 Ma gully activity and surficial meltwater origin

The origin of gullies on Mars is controversial (e.g., catastrophic groundwater release, debris flows, dry granular flows, or meltwater from surface ice and snow) and their ages are difficult to determine due to their small size. We describe a gully depositional fan that contains a unique chronostratigraphic marker (secondary crater clusters) between episodes of gully activity during fan development. This marker can be traced to its source, a 7-km-diameter rayed crater that we have dated as ca. 1.25 Ma. This age links gully activity to the emplacement of dust-ice mantling deposits interpreted to represent recent ice ages on Mars. This association, together with multiple episodes of depositional fan formation, favors an origin for these gullies from top-down melting of snow and ice during multiple favorable spin-axis and orbital variations. This melting mechanism is consistent with the occurrence of gullies in unique steep-sloped, poleward-facing insolation microenvironments that favor the melting of small amounts of surficial snow and ice.

Regional differences in gully occurrence on Mars: A comparison between the Hale and Bond craters

The observation of gullies on Mars raised questions about the presence of liquid water in the recent past. In some regions like Hale and Bond crater, gullies occur in one crater (Hale) but do not in another crater nearby (Bond). These regional differences have been interpreted as an argument for a formation of the gullies related to groundwater. The formation of gullies on Earth depends on rainfall and/or melting of snow as well as on several parameters such as the presence of steep slopes and sufficient amounts of fines and debris. We investigated the Hale/Bond region for differences in crater wall morphology and texture, slopes, and thermal properties to determine whether the gully formation is dependent on factors such as steep slope angles and availability of fine-grained material. Morphologically there exist two kinds of gullies in the Hale crater: Gullies on the south- and east-facing crater slopes have a pristine appearance with deep channels eroded into the talus material and well-preserved aprons. Gully-like features on the north- and west-facing slopes are degraded and superposed by craters, indicating that they are old in comparison to the pristine ones. However, their formation process is unclear and might be due to debris flows, surface runoff or dry mass wasting processes or a combination of these processes. The crater walls of Bond do not show gullies. Their morphology is most likely consistent with a degraded mantle deposit. Slope measurements reveal that the gullies in Hale crater occur on slopes between ∼20° and ∼30° in contrast to the slopes without gullies in Bond that are between ∼10° and ∼20° steep. Mean thermal inertia values on slopes with younger gullies are ∼175 J m −2 K −1 s −1/2 corresponding to higher amounts of fine-grained material. At slopes with older gully-like features mean thermal inertia values are ∼315 J m −2 K −1 s −1/2 corresponding to higher amounts of bedrock or possibly indurated grain sizes. Mean thermal inertia values of the Bond crater walls are ∼230 J m −2 K −1 s −1/2 indicating more consolidated terrain possibly due to the cementation of the dissected mantle material. From our investigation we conclude that the occurrence of gullies in the Hale/Bond region most likely depends on the distribution of unconsolidated material and steep slopes. The regional and local gully distribution on Mars likely varies due to differences in topography and surface material properties. Their proposed clustered distribution on Mars is not an argument for a groundwater formation mechanism of the gullies.