Evaluation of Soil Erosion and Its Prediction Protocols around the Hilly Areas of Mubi Region, Northeast Nigeria

Soil erosion is a severe degradation phenomena that has since received huge attention among earth scientists in the developed worlds, and same efforts are now extending to Africa and other parts of underdeveloped worlds. This chapter focuses on collation, analyzing and appraising of soil ero¬sion studies around Mubi region, Northeast Nigeria, where the Mandara mountain ranges is notably responsible for spurring soil erosion. This chapter reviewed reports on the: (a) Mubi regional soil properties, erosion processes and principles of their occurrence, (b) soil erosion predictions using empirical and physically-based models by researchers, and, (c) economicimplications and managements of soil erosion in the region. This chapter reveals that classical and rill/ephemeral gully (EG) erosion features received more research attention than surface erosion such as splash and sheet. No information was reported on effects of landslides/slumping noticeable along rivers/stream banks around the region. The few economic analysis reported for soil nutrient and sediments entrained by concentrated flow channels were very high and intolerable to the predominantly peasant farmers in the region. It is hoped that the considerable volumes of erosion researches and recommendations assembled in this chapter shall be carefully implemented by prospective farmers, organizations, and residents in the Mubi region.

Morphodynamics of Gully Development on the Platform–Slope System of Spoil Dumps under Platform Concentrated Flow

Severe gully erosion on spoil dumps, caused by dense concentrated flow derived from platforms, poses a significant threat to the land management of mining areas. However, little is known about the development processes and mechanisms of gullies on spoil dumps. A flow scouring experiment was conducted on an established platform–slope system under 3.6–5.04 m3 h−1. The soils of the system consisted of a surface sandy loam A layer and anunderlying clay loam B layer. The results showed that the platform exhibited a gully development process of headcut-incision–headcut-expansion–stabilization and the steep slope experienced gully development of A-layer incision–A-layer expansion–B-layer incision–stabilization. The results showed 88.97–100% of Froude Number (Fr) decrement and 47.90–88.97% of Darcy–Weisbach roughness coefficient increment finished in the two incision stages on the steep slope. Gully depth has the most sensitive response to flow hydraulics. A significant linear correlation exists between gully depth and shear stress, runoff power, Fr, and Reynolds Number (R2 > 0.337). Overall, the optimal hydraulic indicator varies within different stages for describing the gully morphology development, illustrating the different action mechanism between flow hydraulics and gully morphology. Our findings provide a theoretical support for future mechanistic studies of gully erosion and the land management on spoil dump.

Abstract 1122‐000063: Postoperative Recanalization Factors of Coil Embolization for Cerebral Aneurysms with Comparable Volume Embolization Ratio

Introduction : Volume embolization ratio (VER) has been reported to be involved in postoperative recanalization of coil embolization. However, despite comparable VER, some cases remained stable, and the others showed recanalization. Hemodynamic and morphological factors, as described in previous studies, may also influence recanalization in addition to VER. In this study, we focused on cerebral aneurysms treated by coil embolization with comparable VER. Blood flow analysis using computational fluid dynamics (CFD) and geometrical measurements were performed to investigate the recanalization factors. Methods : We focused on the aneurysms that underwent coil embolization with 15–20% VER. The criteria for the case selection were that the size of the aneurysms was 5–10 mm and that the aneurysm was treated by only coil (i.e., the stent‐assisted cases were excluded). Aneurysms that recanalized after coil embolization and underwent additional coil deployment were defined as “recanalized”, and aneurysms that remained stable after coil embolization without coil compaction were defined as “stable”. Finally, we selected 7 recanalized cases (ICA: 1, MCA: 3, ACA: 3) and 18 stable cases (ICA: 6, MCA: 3, ACA: 9). CFD analysis and morphometry were performed on the vessel geometry after coil embolization. The coil shape was modeled by the virtual coil technique. We calculated three morphological parameters and 34 hemodynamic parameters, then we compared them between the recanalized and stable cases using the Mann‐Whitney U test to identify recanalization factors. In addition, we reconstructed the coil shape from medical images and compared its structure and flow characters for stable and recanalized cases. Results : The average VER for the cases analyzed in this study were 16.7% for recanalized cases and 17.7% for stable cases. As hemodynamic parameters, the spatially averaged velocity normal to the neck plane into the cerebral aneurysm ( NV neck ), and the ratio of the area where blood flows into the cerebral aneurysm after the coil embolization to the area of the neck surface (inflow area ratio: IAR) showed significant difference. Although the hemodynamic parameters were significantly different, morphological parameters did not show statistically significance. In the recanalized case, NV neck tended to be higher (mean value, recanalized: 0.931, stable: 0.822, P < 0.05), and IAR tended to be lower (mean value, recanalized: 0.319, stable: 0.408, P < 0.01). The high NV neck and low IAR indicate that the aneurysm had concentrated flow with a high velocity at the neck surface. There was the concentrated blood flow with the high velocity that collided with the modeled coil in a CFD result for the recanalized case. The area where the blood flow impinged on the modeled coil coincided with the compacted coil region reconstructed from medical images. Therefore, a large force on the coil indicated by these hemodynamic parameters may cause the postoperative recanalization. Conclusions : Even with the same level of VER, there was a possibility of recanalization in aneurysms with a high velocity and concentrated flow into the aneurysm. It is necessary to consider not only VER but also hemodynamic factors to investigate recanalization factors after the coil embolization.

Thermal Processing and Testing for the Heat Blow Materials by Concentrated Flow of Electromagnetic Energy

The purpose of this work is to experimentally prove the possibility of modifying the surface of a material by exposure to a long-lived plasma formation (DPO). Under this action, the surface of the material experiences heat shock, since the contact time is about 100 ms. The paper deals with the usage of autonomous long-lasting plasm formations (DPO). The tasks of thermal processing, coating, thermal shock tests metallic and non-metallic materials are introduced in the given paper. Large stored energy (till 10 kJ) and high brightness temperature (4 500 K) at sufficient time of influence can determine the range of technological problems, where long-lasting plasma formations have advantages in comparison with plasmatrons. This paper presents the results of the tests of the thermal shock by the concentrated flow of electromagnetic energy, saved by long-lasting plasm formation.

Inferring Sediment Transport Capacity from Soil Microtopography Changes on a Laboratory Hillslope

In hillslope erosion modeling, the Transport Capacity (Tc) concept describes an upper limit to the flux of sediment transportable by a flow of given hydraulic characteristics. This widely used concept in process-based erosion modeling faces challenges due to scarcity of experimental data to strengthen its validity. In this paper, we test a methodology that infers the exceedance of transport capacity by concentrated flow from changes to soil surface microtopography sustained during rainfall-runoff events. Digital Elevation Models (DEMs) corresponding to pre- and post-rainfall events were used to compute elevation change maps and estimate spatially-varying flow hydraulics ω taken as the product of flow accumulation and local slope. These spatial data were used to calculate a probability of erosion PE at regular flow hydraulics intervals. The exceedance of Tc was inferred from the crossing of the PE = 0.5 line. The proposed methodology was applied to experimental data collected to study the impact of soil subsurface hydrology on soil erosion and sediment transport processes. Sustained net deposition occurred under drainage condition while PE for seepage conditions mostly stayed in the net erosion regime. Results from this study suggest pulsating erosion patterns along concentrated flow networks with intermittent increases in PE to local maxima followed by declines to local minima. These short-range erosion patterns could not be explained by current Tc-based erosion models. Nevertheless, Tc-based erosion models adequately capture observed decline in local PE maxima as ω increased. Applying the proposed approach suggests a dependence of Tc on subsurface hydrology with net deposition more likely under drainage conditions compared to seepage conditions.

Structural, Hydrologic, and Sediment Connectivity in a Shrub-Encroached and Restored Semiarid Grassland

&lt;p&gt;Shrub encroachment of semiarid grasslands is influenced by connected runoff and erosion patterns that preferentially accumulate resources under vegetated patches (canopy microsites) and deplete interspaces. Soil loss from dryland hillslopes results when areas of bare ground become structurally and functionally connected through overland flow. Although these patterns have been well-described, uncertainty remains regarding how these feedbacks respond to restoration practices. This study compared the structure and hydrologic function of a shrub-encroached semiarid grassland treated five years prior with the herbicide, tebuthiuron, to that of an adjacent untreated grassland. Through a series of hydrologic experiments conducted at increasing spatial scales, vegetation and soil structural patterns were related to runoff and erosion responses. At a fine scale (0.5 m&lt;sup&gt;2&lt;/sup&gt;), rainfall simulations (120 mm&amp;#183;h&lt;sup&gt;-1&lt;/sup&gt; rainfall intensity; 45 min) showed herbicided shrub canopy microsites had greater infiltration capacities (105 and 71 mm&amp;#183;h&lt;sup&gt;-1&lt;/sup&gt; terminal infiltration rates) and were less susceptible to splash-sheet erosion (3 and 26 g sediment yield) than untreated shrub canopy microsites, while interspaces were statistically comparable between study sites. Concentrated flow simulations at a coarse scale (~9 m&lt;sup&gt;2&lt;/sup&gt;) revealed that gaps between the bases of vegetation (i.e. basal gaps) &gt; 2 m&lt;sup&gt;&lt;/sup&gt;were positively related to both concentrated flow runoff (r = 0.72, p = 0.008) and sediment yield (r = 0.70, p = 0.012). Modeled hillslope-scale (50 m&lt;sup&gt;2&lt;/sup&gt;) runoff and erosion (120 mm&amp;#183;h&lt;sup&gt;-1&lt;/sup&gt; rainfall intensity; 45 min) indicated less soil loss in the tebuthiuron-treated site (1.78 Mg&amp;#183;ha&lt;sup&gt;-1&lt;/sup&gt; tebuthiuron; 3.19 Mg&amp;#183;ha&lt;sup&gt;-1&lt;/sup&gt; untreated), even though runoff was similar between sites. Our results suggest interspaces in shrub-encroached grasslands continue to be runoff sources following herbicide-induced shrub mortality and may be indicators of runoff responses at larger spatial scales. In contrast, sediment sources are limited post-treatment due to lesser sediment detachment from sheet-splash and concentrated flow processes. Reduced sediment supplies provide evidence that connectivity feedbacks that sustain a shrub-dominant ecological state may have been dampened post-treatment. Our study also highlights the utility of simple measures of structural connectivity, such as basal gaps, as an indicator of hillslope susceptibility to increased runoff and erosion.&lt;/p&gt;