Recent Megafires Provide a Tipping Point for Desertification of Conifer Ecosystems

Recent megafires and gigafires are contributing to the desertification of conifer forest ecosystems due to their size and severity. Megafires have been increasing in their frequency in the past two decades of the 21st century. They are classed as such because of being 40,469 to 404,694 ha in size, having high complexity, resisting suppression, and producing desertification due to erosion and vegetation type conversion. Increasingly, gigafires (>404,694 ha) are impacting coniferous forest ecosystems. These were once thought of as only pre-20th century phenomena when fire suppression was in its infancy. Climate change is an insidious inciting factor in large wildfire occurrences. Fire seasons are longer, drier, hotter, and windier due to changes in basic meteorology. Conifer forests have accumulated high fuel loads in the 20th and 21st centuries. Ignition sources in conifer forests have increased as well due to human activities, economic development, and population demographics. Natural ignitions from lightning are increasing as a result of greater severe thunderstorm activity. Drought has predisposed these forests to easy fire ignition and spread. Wildfires are more likely to produce vegetation shifts from conifers to scrublands or grasslands, especially when wildfires occur with higher frequency and severity. Severe erosion after megafires has the collateral damage of reducing conifer resilience and sustainability.

Numerical investigation on adsorbent particle erosion characteristic of Y-shaped pipeline in S Zorb regeneration system with different influencing parameters

As the transportation pipeline of adsorbent in S Zorb regeneration system, due to large mass flow rate of particle and gas, it is often seriously worn, and even perforated, resulting in the leakage of adsorbent. It brings great inconvenience to the transportation of regenerated adsorbent and threats its long-term operation. Therefore, it is essential to study the erosion characteristic of Y-shaped adsorbent transportation pipe. It was studied by computational fluid dynamics (CFD) numerical simulation and the calculation results were validated by actual erosion profile. The results show that the high velocity of nitrogen and the high weight-fraction adsorbent particles accumulation is the key factor leading to severe erosion. It is also found that the small angle cutting is the erosion form. The effects of the intersection angle between the transportation pipe and feed pipe and the gas inlet velocity on the particle motion and erosion characteristics turn out to be significant. The research on the wear characteristics of adsorbent transportation pipeline can provide a certain reference for erosion prevention and optimization.

Spatial and temporal characteristics of soil erosion in a typical karst basin in southwest China and its response to the landscape pattern of rock desertification

Soil erosion is a process of migration and redistribution of soil substances in the landscape, which is regulated by topography, vegetation, human activities and their spatial pattern. At the watershed scale, changes in landscape pattern are important factors in determining the degree of soil erosion. Taking Dabang River Basin as the study area, based on the three phases of land use data, remote sensing image data and daily rainfall data from eight stations in the basin in 2010, 2015 and 2020, the rocky desertification factor (D) was introduced into the general soil loss equation RUSLE to calculate the soil erosion in Karst and non-Karst Areas in 2010, 2015 and 2020 respectively. The relationship between landscape pattern and soil erosion was analyzed from two aspects: type level index and landscape level index. The results showed that: 1) From 2010 to 2020, the average soil erosion modulus in The Dabang River Basin decreased first and then increased. The average soil erosion modulus in the non-karst region was about twice that in the karst region, and the average soil erosion modulus in the karst region decreased first and then increased. The mean soil erosion modulus in the non-karst area showed an increasing trend; 2) Under different slope grades, the erosion was mainly slight and mild, and the area of slight erosion was the largest, and the area of very strong and severe erosion increased as the slope increased. the area of strong, very strong and severe erosion increased in the slope zone below 15°, the area of light and moderate erosion decreased, and the area of slight, strong and very strong erosion increased in the slope zone from 15 to 25°, and the area of slight erosion increased in the slope zone above 25° area increased and light, moderate and strong erosion area decreased in the slope zone above 25°; 3) The landscape pattern of the Dadang River Basin changed significantly from 2010 to 2020. At the landscape level, the number of patches increased and the average patch area decreased. At the type level, the area of paddy field, woodland and shrubland decreases and the area of dry land, grassland, construction land and water body increased, and the dominant land type in the watershed changed from woodland to grassland; 4) The amount of soil erosion was positively correlated with patch type area, landscape percentage, maximum patch index and aggregation index, and positively correlated with edge density; 5) There was a linear relationship between soil erosion and Shannon diversity index (SHDI) and Shannon mean index (SHEI) at landscape level. The results can provide reference for land use planning and soil and water conservation measures.

Satellite-Derived Topography and Morphological Evolution around Authie Macrotidal Estuary (France)

The wide spatial and temporal coverage of remotely sensing images is an essential asset to analyze the morphological behaviour of fast-changing coastal environments such as estuarine systems. This paper investigates the reliability of intertidal topography mapping around the Authie Bay, a macrotidal estuarine system located on the northern coast of France. A Satellite-Derived Topography technique is developed by relating the green band reflectance of Sentinel-2 images to rapid variations in topography. This method is well suited to small sedimentary structures of the coastal zone with a 0.30 to 0.35 m height accuracy of the constructed Digital Elevation Model (DEM). For the more complex estuarine configuration, the waterline method was applied and resulted in the construction of DEMs with a height accuracy of 0.35 to 0.38 m. Video animations and records of Authie meander positions along transects are created from Sentinel-2 and Landsat satellite archives (1984–2020). These materials allow to highlight a sedimentation phase at the east side of the spit since 2015. It constrains the main channel towards the eastern bank, thus promoting coastal erosion. The monitoring of a severe erosion phase throughout 2019 shows a 130 m retreat of the coastline. Topographic map differentiation led to the detection of a sedimentation anomaly upstream of the bay, probably linked to this erosion event.

Wildfire burn scar encapsulation

Wildfires burn annually across the United States (US), which threaten those in close proximity to them. Due to drastic alterations of soil properties and to the land surfaces by these fires, risks of flash floods, debris flows, and severe erosion increases for these areas, which can have catastrophic consequences for biota, people and property. Computational tools, such as the WildfireRain algorithm, have been designed and implemented to assess the potential occurrence of debris flows over burn scars. However, in order to efficiently operate these tools, they require independent, non-overlapping buffers around burned areas to be defined, which is not a trivial task. In this paper we consider the problem of efficiently subsetting the conterminous US (CONUS) domain into optimal subdomains around burn scars, aiming to enable domain-wide WildfireRain product outputs to be used for operations by the National Weather Service (NWS). To achieve this, we define the Object Encapsulation Problem, where burn scars are represented by single-cell objects in a gridded domain, and circular buffers must be constructed around them. We propose a Linear Programming (LP) model that solves this problem efficiently. Optimal results produced using this model are presented for both a simplified synthetic data set, as well as for a subset of burn scars produced by severe wildfires in 2012 over the CONUS.

Effects of biological works within the integrated watershed management of torrent catchments in the area of Grdelica Gorge and Vranjska Valley (Serbia)

Integrated watershed management is based on the application of various biological and technical works, and administration measure to reduce the degradation process. The paper presents an analysis of the effects of performed biological works as part of integrated watershed management within the Grdelica Gorge and Vranjska Valley. Extensive erosion control works were carried out in the second half of the 20th century. As vegetation is one of the key factors in mitigating the erosion process, the paper presents the trend of connecting the surface with the vegetation cover, which results from implemented biological measures. Using multispectral satellite imagery (Landsat missions) for 1972, 1986, 1996, and 2017, the vegetation index (Normalized Difference Vegetation Index – NDVI) was analyzed in torrent basins, which were afforested to control severe erosion processes. The increasing trend of vegetated areas was recorded in period from 1986 to 1996 (very low vegetation coverage 40.19 % in 1986 and 8.19 % in 1996, respectively), which continues to grow until 2017 when the very low vegetation coverage was 0.26 %, and moderately high vegetation coverage was 50.63 %.

The Making of a Gravel Beach (Cavo, Elba Island, Italy)

This paper presents the history and evolution of the different projects carried out from 1999 to 2008 at Cavo beach in the Elba Island, Italy. The village of Cavo almost completely lost its beach in the 1970s due to the reduction of sedimentary input, and the backing coastal road was defended by a revetment and two detached breakwaters. Such severe erosion processes continued in the following years and impeded any possibility of beach tourist development. In 1999, a project based on the removal of existing breakwaters and beach nourishment works based on the use of gravel as borrow sediment and the construction of two short groins to maintain nourished sediment, raised environmental concern and did not find the approval of the stakeholders. They were worried about the characteristics of the sediments, i.e., waste materials from iron mining rich in red silt and clay. Such sediment fractions made the sea red during the nourishment and deposited on the Posidonia oceanica meadow in front of the beach, with a potential environmental impact. Furthermore, they cemented the gravel fraction forming a beach rock. Between 2006 and 2008, these materials were covered with better quality gravel, extending and raising the beach profile, which required the elevation and lengthening of the two existing groins. Beach evolution monitoring following the second project, based on morphological and sedimentological data acquired before, during and after the works, demonstrated the great stability of the newly created beach. The wider beach has allowed the construction of a promenade and the positioning, in summer, of small structures useful for seaside tourism, increasing the appeal of this village. Data presented in this paper shows an interesting study case, since few examples exist in international literature regarding gravel nourishment projects monitoring and evolution.

Coastal Erosion And Tourism: The Case Of The Distribution Of Tourist Accommodations And Their Daily Rates

Beaches are key territories for tourist development but at risk of impacts of climate change—specifically with the consequent intensification of coastal erosion. This study examines the effects of coastal erosion on the distribution of lodging facilities and the value of daily rates practiced on the beaches of Tabuba and Cumbuco on the northeast coast of Brazil. The methodology comprises collecting information on the means of accommodation (distribution and daily rate), quantifying coastline variation and measuring the field to validate data. A total of 13.9 km of coastline were analyzed; erosion tendency was observed in 26.8% of the coast (9.0% erosion, 14.4% intense erosion, and 3.4% severe erosion). With the highest erosion rates, Tabuba's Beach has a low density in accommodation distribution and daily rates practiced in tourism. Cumbuco's Beach, conversely, has a lower risk of erosion, and the means of accommodation are concentrated. Coastal erosion has affected tourism development in Caucaia, influencing the choice of tourism accommodation entrepreneurs. the results indicate that there is a clear concentration of tourist accommodations in areas without notorious problems with coastal erosion, influencing in the distribution of tourist facilities and their daily rates. So, there is a direct connection does exist between local tourism system income and the beaches with problems with coastal erosion.

In Situ Stress and Stress Regime in the Onshore Part of the Northeast Java Basin

In situ stress is importance in the petroleum industry because it will significantly enhance our understanding of present-day deformation in a sedimentary basin. The Northeast Java Basin is an example of a tectonically active basin in Indonesia. However, the in situ stress in this basin is still little known. This study attempts to analyze the regional in situ stress (i.e., vertical stress, minimum and maximum horizontal stresses) magnitude and orientation, and stress regime in the onshore part of the Northeast Java Basin based on twelve wells data, consist of density log, direct/indirect pressure test, and leak-off test (LOT) data. The magnitude of vertical ( and minimum horizontal ( stresses were determined using density log and LOT data, respectively. Meanwhile, the orientation of maximum horizontal stress ( was determined using image log data, while its magnitude was determined based on pore pressure, mudweight, and the vertical and minimum horizontal stresses. The stress regime was simply analyzed based on the magnitude of in situ stress using Anderson’s faulting theory. The results show that the vertical stress ( ) in wells that experienced less erosion can be determined using the following equation: , where is in psi, and z is in ft. However, wells that experienced severe erosion have vertical stress gradients higher than one psi/ft ( . The minimum horizontal stress ( ) in the hydrostatic zone can be estimated as, while in the overpressured zone, . The maximum horizontal stress ( ) in the shallow and deep hydrostatic zones can be estimated using equations: and , respectively. While in the overpressured zone, . The orientation of is ~NE-SW, with a strike-slip faulting stress regime.