No-tillage implementation: Analyzis on water-based sediment flow in the Marombas River, Brazil

ABSTRACT Water erosion is influenced by climate, soil, soil cover and soil conservation practices. These factors can be modified by natural (especially climate) and/or anthropogenic (especially soil, soil cover and conservation practices) actions. The relief factor also influences the water erosion and can also be partially modified by anthropic action. This study aimed to evaluate the impact of anthropogenic action due to the introduction of soil crop in no-tillage system on water erosion, and on the consequent flow of sediments in the water. The study was carried out in the Marombas river basin with an area of 3,939 km², using the Soil Water Assessment Tools (SWAT) model. The calibration and validation of the model for sediment production was carried out with a historical series of synthetic data. The data from this series were estimated by linear regression from sediment value load and the average daily flow obtained punctually in the basin’s outlet. The SWAT model was calibrated on a daily scale with data from 1979 to 1989 and was validated with data from 1994 and 1997. The SWAT model was suitable to represent the average daily flow and sediment flow in the Marombas watershed. The hypothesis of reduced sediment production with increasing soil crop in no-tillage system was accepted.

Agricultural intensification vs climate change: What drives long-term changes of sediment load?

Climate change and agricultural intensification are expected to increase soil erosion and sediment production from arable land in many regions. However, so far, most studies have been based on short-term monitoring and/or modeling, making it difficult to assess their reliability in terms of long-term changes. We present the results from a unique data set consisting of measurements of sediment loads from a 60ha catchment (the HOAL Petzenkirchen in Austria) over a time window spanning 72 years. Specifically, we compare Period I (1946–1954) and Period II (2002–2017) by fitting sediment rating curves for the growth and dormant seasons for each of the periods. The results suggest a significant increase in sediment yield from Period I to Period II with an average of 11.6 ± 10.8 ton·yr−1 to 63.6 ± 84.0 ton·yr−1. The sediment flux changed mainly due to a shift of the sediment rating curves (SRC), given that the annual streamflow varied little between the periods (5.6 l·s−1 and 7.6 l·s−1, respectively, on average). The slopes of the log regression lines of the SRC for the growing season and the dormant season of Period I were 16.72 and 4.9, respectively, whilst they were 5.38 and 1.17 for Period II, respectively. Climate change, considered in terms of rainfall erosivity, was not responsible for this shift, given that erosivity decreased by 30.4 % from the dormant season of Period I to that of Period II, and no significant difference was found between the growing seasons of Periods I and II. However, the sediment flux changes can be explained by changes in crop type and parcel structure. During low and median streamflow conditions (i.e. Q < Q20 %), land consolidation in Period II (i.e. theparcel effect) did not exert an apparent influence on sediment production. Whilst with increasing stream flow (Q > Q20 %), parcel structure played an increasingly role in sediment yield contribution, and leading to a dominant role due to enhanced sediment connectivity in the landscape at extremely high flow conditions (i.e. Q > Q2 %). The increase in cropland in Period II at the expense of grassland had an unfavourable effect on sediment flux, independent of streamflow, with declining relevance as flow increased. We conclude that both land cover change and land consolidation should be accounted for simultaneously when assessing sediment flux changes. Especially during extremely high flow conditions, land consolidation substantially alters sediment fluxes, which is most relevant for long-term sediment loads and land degradation. Increased attention to improving parcel structure is therefore needed in climate adaptation and agricultural catchment management.

The risk reduction effect of sediment production rate by understory coverage rate in granite area mountain forest

Ecosystem-based disaster risk reduction (Eco-DRR) is an important concept to the adaption of climate change for a sustainable life. In Japan, it is anticipated that damages caused by sediment production will be increased as the intensity and amount of rainfall are increased by climate change. Thus, we need to know the Eco-DRR effect of the forest for planning sustainable land use by evidence-based data. In this study, we focused on the relationship between sediment production rate and the understory coverage rate of a low mountain forest in the granite area. From the results of the field survey and statistical meta-analysis, the sediment production rate was reduced by 97% in granite area mountain forest when the understory coverage rate was 60% or more compared to when less than 30% by evidence-based data. Accordingly, we found that it will be necessary to keep forests with an understory coverage rate of 60% or more when considering the risk-reducing effect of sediment disaster in granite area mountain forests for the adaption of climate change.

Modeling landslide susceptibility and landslide volume per geomorphologic landform unit

The analysis of landslide susceptibility and landslide volumes in landforms can provide information for planning disaster management in an area. Landslide susceptibility per landform unit and the potential contribution of material delivered from each unit was calculated for a 105 km2 watershed on the south flank of Pico de Orizaba volcano, Mexico. The landslide susceptibility is calculated from the area and frequency of landslides. The volume is obtained from detailed geometric values of shallow landslides in order to establish an empirical relationship that takes the form of a power law from which the potential volume of all shallow landslides is calculated for the watershed. The study shows that most of the landslides are on volcanic landform units; however, the landslides in sedimentary units contribute more sediments per square kilometer. It also shows that landform units can be used to explain the predisposition and variability of landslide sediment production for a large and complex geological watershed.

Multi-Hazard Susceptibility Assessment: Case Study – Municipality of Štrpce (Southern Serbia)

The Municipality of Štrpce (Southern Serbia) is an area located within the Šar Mountain National Park, and due to its great ecological importance, it was necessary to analyze the terrain susceptibility to the occurrence of natural hazards. The main goal of this research is to determine the locations that are most susceptible to natural hazards (earthquakes, erosion, torrential flooding, snow avalanches and forest fires) on the territory of the municipality of Štrpce. By utilizing the geographic information systems (GIS), the first step was to analyze seismic hazard for a 475-year return period (VII-VIII MCS for the observed area). The second step was to determine the intensity of erosion and total sediment production using erosion potential model (EPM). The mean erosion coefficient is quantified to 0.34, and the total sediment production is 131.795 m3/year. The third step was the analysis potential of torrential floods using the Flash Flood Potential Index (FFPI). This method indicated that 43.33% of the municipality is highly susceptible, and 18.86% is very highly susceptible to torrential floods. The Avalanches Potential Index (AVAPI) method was used for the fourth step which involved determining the area prone to the occurrence and movement of avalanches. It was determined that 9.1 km2 of the municipality area is susceptible to this type of hazard. The fifth step included the analysis of the terrain susceptibility to the occurrence of forest fires. More than half of the municipal area (52.4%) is highly susceptible, and 8.5% is very highly susceptible to forest fires. Following the five criteria analysis, weight coefficients were assigned for each of the analyzed parameters using the analytical hierarchy process (AHP), giving the result of the total susceptibility of the territory of Štrpce to natural hazards. Results indicated that over 45% of the municipality is highly or very highly prone to various natural hazards. This paper presents a significant step towards better understanding and more adequate management and mitigation of natural hazards not only in the investigated area, but on regional and national levels as well.

Assoreamento nas baías de Antonina e de Paranaguá – PR: análise integrada das áreas fontes de sedimentação e obras de dragagem

A segurança à navegação é um fator primordial para garantir aos navios acesso aos portos. Obras de dragagens são necessárias para a manutenção dos canais de navegação diante do processo de assoreamento em regiões estuarinas. Entretanto, o volume, em metros cúbicos dragados, na região portuária do Complexo Estuarino de Paranaguá (CEP), aumentou ao longo do tempo. O presente estudo se restringe aos setores que interessam à navegação e às instalações portuárias, isto é, o eixo E-W do CEP, que abrange os trechos do canal de acesso aos portos paranaenses nas baías de Paranaguá e Antonina. O total de sedimentos realocados entre 1999 e 2018 nos trechos do canal foi da ordem de 42.517.662,79 m³. A manutenção destes setores é extremamente onerosa, uma vez que mais de 4.000.000 m³.a-1 de material sedimentar são retirados atualmente para garantir acessibilidade aos navios. Ao estimar a produção de sedimentos na área de drenagem do CEP, obteve-se o valor anual de 197.017,23 ton. Dessa forma, torna-se necessário desenvolver estratégias para a retenção de sedimentos nas áreas fonte, a fim de garantir a prosperidade das atividades portuárias nos próximos anos. Recomendações à expansão dos portos na região foram apresentadas ao final. Silting in the Bays of Antonina and Paranaguá - PR: Integrated Analysis of Sedimentation Sources and Dragging WorksA B S T R A C TSafety in navigation is a primordial aspect to the ports. Dredging works are necessary for the maintenance of the navigation channels before the process of silting in estuarine regions. However, the volume in cubic meters dredged in the port region of the Paranaguá Estuary Complex (CEP) has increased over time. This study is restricted to sectors that are of interest to navigation and to port installation, in other words, the E-W axis of the CEP that includes the sections of the access channel to the ports of Paraná in the bays of Paranaguá and Antonina. The total of relocated sediments between 1999 and 2018 in the canal segments is of the order of 42.517.662,79 m³. The maintenance of these sectors becomes extremely costly, since more than 4.000.000 m³.a-1 of sedimentary material is removed to guarantee accessibility to the ships. When estimating the sediment production in the CEP drainage area, the annual value of 197,017.23 tons is obtained. Thus, it becomes necessary to develop strategies for retaining sediments in the source areas, in order to guarantee the prosperity of port activities in the coming years. Recommendations for expanding ports in the region were presented at the end.Keywords: Hydrographic Units. Sedimentary Dynamics. Sedimentary Disposal. Port Environmental Management.

Intraplate deformations, topographic evolution and sediment production of Western Europe from 40 to 5 Myrs

&lt;p&gt;Western Europe experienced a major rift system initiated during Bartonian times (41 Ma). This evolution is coeval with long wavelength deformations (several hundreds of kilometers) that control the topography and the sediment production beyond the rift. The climate during this time interval was first increasingly arid and then wetter.&lt;/p&gt;&lt;p&gt;This study is based on both landform and sediment analysis of southern England, France, Belgium and western Germany. The landforms are mainly large pediments, dated by the intersection with sediments deposited in low to high subsiding areas and volcanism. A set of paleogeographic maps with paleotopographic reconstructions, is used to constrain the uplifting and subsiding areas, their wavelength and the critical periods of intraplate deformations.&lt;/p&gt;&lt;p&gt;The main periods of deformations and sedimentary systems changes area as follow.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;41&lt;/strong&gt;Myrs (base Bartonian) was the beginning of a major tilting of Western Europe with subsidence of France and uplift of the Brabant/Ardennes/Rhenish Massif. Even a dense network of basement faults was reactivated, biochemical sedimentation prevailed.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;35-31&lt;/strong&gt;Myrs (Late Priabonian-Early Rupelian) initiated a period of general subsidence even along the Ardennes/Rhenish Massif and the French Massif Central. Two major marine floodings are recorded, with a differential preservation according to the balance between deformation and eustasy.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;27-25&lt;/strong&gt;Myrs (Chattian) was a period of uplift of Western Europe except the Aquitaine Basin, followed by a relaxation favoring eustatic floodings in (very) low subsiding domains. Chattian siliciclastic deposits are preserved as lowstand wedges in the surrounded basins (North Sea, Atlantic Margin).&lt;/p&gt;&lt;p&gt;&lt;strong&gt;14-11&lt;/strong&gt;Myrs (Serravallian-Early Tortonian) initiated the overall uplift of Western Europe, still operating today. This is the beginning of a period of major denudation in southern England, Western Germany (SW Germany flat - &amp;#8220;Stufenland&amp;#8221;) and along the southern limb of the Franch Massif Central.&lt;/p&gt;&lt;p&gt;The causes and the consequences in term of sediment production are discussed.&lt;/p&gt;

Spatial variation in sediment fluxes along the western slopes of the Peruvian Andes

&lt;p&gt;Knowledge of sediment production mechanisms and their potential controlling factors contributes to our understanding of geomorphological processes. Previous studies highlighted the link between sediment yield and anthropogenic (e.g. agricultural practices) and natural factors (e.g. climate, topography, river runoff, lithology and vegetation cover). The rugged western slopes of the Peruvian Andes shows different climate regimes with arid climates and desertic vegetation in the south and tropical climates and abundant vegetation in the north. In this region, agricultural and water regulation projects are concentrated.&lt;/p&gt;&lt;p&gt;However, the number of studies on sediment yield and its controlling factors are limited along the Peruvian Andes. Most studies on the western slopes have focused on the Northern part of Peru and showed a 3 to 60 times increase of sediment yield during El Ni&amp;#241;o (ENSO) events compared to normal years. The storm events rapidly mobilized sediment that was accumulated in the mountain and piedmont areas during dry normal years. In the central part of Peru where the main reservoirs, irrigation systems, and water supply plants are located, few studies were realized. They concluded that the relation between sediment production and both environmental and anthropogenic controlling factors needs to be further explored.&lt;/p&gt;&lt;p&gt;In this study, we identify the spatial patterns of sediment yield along the western slopes of the Peruvian Andes and analyze the main environmental controlling factors. Our study presents data on sediment yield of 20 catchments. The data contains information on suspended sediment load from gauging stations, reservoir sedimentation and water turbidity. We used satellite-based data to derive topographic information (SRTM v.3 DEM by NASA), daily precipitation covering the period 1981 to 2016 (PISCO product by Senamhi), daily discharge covering 1970 to 2020 (GloFAS-ERA5 global river dataset), lithological strength (global lithological map GLiM), and vegetative cover (MODIS Land cover type product). Our first results show a significant influence of the lithology, maximum discharge and topographic relief on sediment yield. The results of the analyses for the Peruvian Andes will be compared with previous studies in the Northern and Southern Andes. &amp;#160;&lt;/p&gt;