Measuring subaqueous progradation of the Wax Lake Delta with a model of flow direction divergence

Abstract. Remotely sensed flow patterns can reveal the location of the subaqueous distal tip of a distributary channel on a prograding river delta. Morphodynamic feedbacks produce distributary channels that become shallower over their final reaches before the unchannelized foreset slopes basinward. The flow direction field over this morphology tends to diverge and then converge, providing a diagnostic signature that can be captured in flow or remote sensing data. A total of 21 measurements from the Wax Lake Delta (WLD) in coastal Louisiana and 317 measurements from numerically simulated deltas show that the transition from divergence to convergence occurs in a distribution that is centered just downstream of the channel tip, on average 132 m in the case of the WLD. These data validate an inverse model for remotely estimating subaqueous channel tip location. We apply this model to 33 images of the WLD between its initiation in 1974 and 2016. We find that six of the primary channels grew at rates of 60–80 m yr−1, while the remaining channel grew at 116 m yr−1. We also show that the subaqueous delta planform grew at a constant rate (1.72 km2 yr−1). Subaerial land area initially grew at the same rate but slowed after about 1999. We explain this behavior as a gradual decoupling of channel tip progradation and island aggradation that may be common in maturing deltas.

Download Full-text

Measuring Subaqueous Progradation of the Wax Lake Delta with a Model of Flow Direction Divergence

10.5194/esurf-2018-47 ◽

2018 ◽

Cited By ~ 1

Author(s):

John B. Shaw ◽

Justin D. Estep ◽

Amanda R. Whaling ◽

Kelly M. Sanks ◽

Douglas A. Edmonds

Keyword(s):

Flow Direction ◽

Remote Sensing Data ◽

Remotely Sensed ◽

Diagnostic Signature ◽

Wax Lake Delta ◽

Coastal Louisiana ◽

Changes Over Time ◽

Direction Field ◽

Over Time ◽

Distributary Channel

Abstract. Remotely sensed flow patterns can reveal the location of the subaqueous distal tip of a distributary channel on a prograding river delta. Morphodynamic feedbacks produce distributary channel tips that become shallower over their final reaches before becoming deeper over the unchannelized foreset. The flow direction field over this morphology tends to diverge and then converge providing a diagnostic signature that can be captured in flow or remote sensing data. Twenty-one measurements from the Wax Lake Delta (WLD) in coastal Louisiana, and 317 measurements from numerically simulated deltas show that the transition from divergence to convergence occurs in a distribution that is centered just downstream of the channel tip, on average 132 m in the case of the WLD. With these data we validate the Flow Direction to Channel tips (FD2C) inverse model for remotely estimating subaqueous channel tip location. We apply this model to 33 remotely sensed images of the WLD between its initiation in 1974 and 2016. We find that the distributaries grew unevenly, 6 of the primary channels grew at rates of 60–80 m/yr while one grew at 116 m/yr. We also estimate the growth rate of the total area enclosed by the subaqueous delta platform to be 1.83 km2/yr with no obvious rate changes over time.

Download Full-text

Grounding and calving cycle of Mertz Ice Tongue revealed by shallow Mertz Bank

The Cryosphere ◽

10.5194/tc-10-2043-2016 ◽

2016 ◽

Vol 10 (5) ◽

pp. 2043-2056 ◽

Cited By ~ 5

Author(s):

Xianwei Wang ◽

David M. Holland ◽

Xiao Cheng ◽

Peng Gong

Keyword(s):

Remote Sensing ◽

Flow Direction ◽

Remote Sensing Data ◽

Sea Surface ◽

Seafloor Topography ◽

Ice Flow ◽

Air Content ◽

Cyclic Variations ◽

Cyclical Process ◽

Height Data

Abstract. A recent study, using remote sensing, provided evidence that a seafloor shoal influenced the 2010 calving event of the Mertz Ice Tongue (MIT), by partially grounding the MIT several years earlier. In this paper, we start by proposing a method to calculate firn air content (FAC) around Mertz from seafloor-touching icebergs. Our calculations indicate the FAC around Mertz region as 4.87 ± 1.31 m. We then design an indirect method of using freeboard and sea surface height data extracted from ICESat/GLAS, FAC, and relatively accurate seafloor topography to detect grounding sections of the MIT between 2002 and 2008 and analyze the process of grounding prior to the calving event. By synthesizing remote sensing data, we point out that the grounding position was localized northeast of the Mertz ice front close to the Mertz Bank. The grounding outlines of the tongue caused by the Mertz Bank are extracted as well. From 2002 to 2008, the grounding area increased and the grounding became more pronounced. Additionally, the ice tongue could not effectively climb over the Mertz Bank in following the upstream ice flow direction and that is why MIT rotated clockwise after late 2002. Furthermore, we demonstrate that the area-increasing trend of the MIT changed little after calving (∼  36 km2 a−1), thus allowing us to use remote sensing to estimate the elapsed time until the MIT can reground on and be bent by the shoal. This period is approximately 70 years. Our observations suggest that the calving of the MIT is a cyclical process controlled by the presence of the shallow Mertz Bank location and the flow rate of the tongue. This calving cycle also explains the cyclic variations in sea-surface conditions around the Mertz detected by earlier studies.

Download Full-text

USE OF MULTISPECTRAL IMAGING IN THE EVALUATION OF BURNINGS AND FOREST FIRES IN KRAHÔLANDIA INDIGENOUS LAND (2003-2014)

FLORESTA ◽

10.5380/rf.v45i4.40078 ◽

2015 ◽

Vol 45 (4) ◽

pp. 853

Author(s):

Lawrence Nóbrega de Oliveira ◽

Gustavo Maximiano Junqueira Lazzarini ◽

Antonio Carlos Batista ◽

Kaio Cesar Cardoso de Lima Fonseca Alves ◽

Marcos Giongo

Keyword(s):

Remote Sensing ◽

Forest Fires ◽

Multispectral Imaging ◽

Remote Sensing Data ◽

Indigenous Communities ◽

Burned Area ◽

Land Area ◽

Burned Areas ◽

Gis Tools ◽

Indigenous Land

AbstractHuman actions change the natural occurrences of wildfire. The indigenous communities, during their time of occupation of the Cerrado, probably utilized fire to manipulate the landscape and its resources. In this study, we mapped and analyzed the spatial distribution of burned areas of the Kraholândia Indigenous Land, from 2003 to 2014, using Remote Sensing resources and GIS tools. During the assessed period, the total burned area extended across 1,516,873 ha, representing 4.94 times the sum of Kraholândia Indigenous Land area (306,871 ha). The average annual burned area was 126,406 ha (41.19%), with the year of the largest burned area recorded at 185,297 ha (60.4%) and the year of the smallest burned area was 71,764 ha (23.4%). There were 29,764 ha (9.7%) that had never been burned during the 12 years, and 1,693 ha (0.6%) that had been burned every year of the period. Moreover, the areas that recorded the highest frequency of fire occurrence and burnings were surprisingly not those that produced the largest burned areas over the period. The remote sensing data, allied with methodology employed, succeeded in identifying the frequency of burnings and wildfire in the Krahôlandia Indigenous Land.ResumoUtilização de imagens multispectrais na avaliação das ocorrências de queimadas e incêndios florestais na Terra Indígena Krahôlandia (2003-2014). As ações humanas alteram as ocorrências naturais dos incêndios e queimadas. Os povos indígenas, quando da ocupação do Cerrado, provavelmente usavam o fogo para manipular a paisagem e os seus recursos em várias épocas do ano. Este trabalho teve por objetivo analisar e mapear a distribuição espacial de áreas queimadas na Terra Indígena Krahôlandia, no período de 2003 a 2014, utilizando ferramentas de sensoriamento remoto e SIG. Nos 12 anos avaliados, a área queimada total foi de 1.516.872,51 ha, que representa 4,94 vezes a área total da TI Krahôlandia (306.871,02 ha). A média anual de área queimada foi de 126.406,04 ha (41,19%) com o ano da maior área queimada com 185,297 ha (60,4%) e o ano da área menor com 71,764 ha (23,4%). Houve 29.764 ha (9,7%) que nunca tinham sido queimadas durante os 12 anos, e 1.693 ha (0,6%) que tinham sido queimados todos os doze anos. Além disso, as áreas que registraram a maior frequência de ocorrência de incêndios e queimadas não foram surpreendentemente aquelas que produziram as maiores áreas queimadas ao longo do período. Os dados de sensoriamento remoto aliados com metodologia empregada conseguiu identificar a frequência de ocorrência de queimadas e incêndios florestais na terra indígena Krahôlandia.Palavras-chave: Cerrado; recorrência de fogo.

Download Full-text

Grounding and Calving Cycle of Mertz Ice Tongue Revealed by Shallow Mertz Bank

10.5194/tc-2016-3 ◽

2016 ◽

Author(s):

Xianwei Wang ◽

David M. Holland ◽

Xiao Cheng ◽

Peng Gong

Keyword(s):

Remote Sensing ◽

Flow Direction ◽

Surface Condition ◽

Remote Sensing Data ◽

Seafloor Topography ◽

Ice Flow ◽

Air Content ◽

Time Period ◽

Level Data ◽

Increasing Trend

Abstract. A recent study, using remote sensing, provided some evidence that a seafloor shoal influenced the 2010 calving event of the Mertz Ice Tongue (MIT), by partially grounding the MIT several years earlier. In this paper, we propose a method to calculate firn air content (FAC) around Mertz from seafloor-touching icebergs. Our calculations indicate the FAC around Mertz region as 4.87 ± 1.31 m. We design an indirect method of using freeboard and sea level data extracted from ICESat/GLAS, FAC, and highly accurate seafloor topography to detect grounding sections of the MIT between 2002 and 2008 and analyze the process of grounding before the calving. By synthesizing remote sensing data, we point out that the grounding position was just localized northeast of the Mertz ice front close to the Mertz Bank. The grounding outlines of the tongue caused by the Mertz Bank are extracted as well, however the length is only limited in several kilometers since late 2002. From 2002 to 2008, the grounding area increased and the grounding became more pronounced. Additionally, the ice tongue could not climb over the Mertz Bank in following the upstream ice flow direction and that is why MIT rotated clockwise after late 2002. Furthermore, we demonstrate that the area-increasing trend of the MIT changed little after calving (~36 km2/a), thus allowing us to use remote sensing to estimate the elapsed time until the MIT can reground on the shoal. This time period is approximately 70 years. The calving of MIT can be repeatable because of the shallow Mertz Bank and the calving cycle of the MIT explains the cycle of sea-surface condition change around Mertz. Keywords: Mertz Ice Tongue, Firn air content, iceberg grounding, Mertz Bank, iceberg scouring, calving cycle.

Download Full-text

Application of Remote Sensing and Geoinformatics Techniques in Erosion Mapping and Groundwater Management in the River Amba Watershed, Central Nigeria

Journal of the Nigerian Society of Physical Sciences ◽

10.46481/jnsps.2021.63 ◽

2021 ◽

pp. 59-65

Author(s):

Aliyu Itari Abdullahi ◽

Nuhu Degree Umar

Keyword(s):

Remote Sensing ◽

Land Use ◽

Groundwater Management ◽

Rainfall Intensity ◽

Flow Direction ◽

Remote Sensing Data ◽

Geological Mapping ◽

Aerial Photographs ◽

Sensing Data ◽

Geoinformatics Techniques

This research integrated easy-to-handle remote sensing data and geoinformatics techniques for erosion mapping and groundwater management in the River Amba watershed, central Nigeria. It is aimed at: (a) the determination of the erosion-prone areas and (b) the estimation of the groundwater potential contamination risk under current and future anthropogenic activities. Rainfall intensity was evaluated from monthly rainfall data (2001 - 2011) from the station located within the River Amba Watershed. Digital Elevation Model (DEM) for the terrain was created using the 3D Analyst tool (Surfer 14) and was used to determine the flow direction and lineament features in each raster cells. Remote sensing data (aerial photographs and LANDSAT imagery) were used to develop a land-use map, while geological mapping was used to determine the local geology of the watershed area. The contributions of the various factors to the erosion hazardous areas are: elevation 31.49 %, land use 21 %, slope 14 %, geology 12.52 %, rainfall intensity 10.5 % and flow accumulation 10.5 %. The combined influences of these factors to erosion susceptibility as either: very high, high, moderate, low, and very low with the south-western part characterized as high while other parts of the study area moderate to very low erosion vulnerability. The groundwater level is shallow (4.0 –28.5 m) and discharges through the Amba river and many springs. These springs along with boreholes and wells supply drinking water to Lafia and the environs.

Download Full-text

Improving canopy variables estimation from remote sensing data by exploiting ancillary information. Case study on sugar beet canopies

Agronomie ◽

10.1051/agro:2002008 ◽

2002 ◽

Vol 22 (2) ◽

pp. 205-215 ◽

Cited By ~ 62

Author(s):

Bruno Combal ◽

Fr�d�ric Baret ◽

Marie Weiss

Keyword(s):

Remote Sensing ◽

Sugar Beet ◽

Remote Sensing Data ◽

Sensing Data ◽

Ancillary Information

Download Full-text

Monitoring land use change in the Lake Taupo catchment between 1975, 1990 and 2002 using satellite remote sensing data

Proceedings of the New Zealand Grassland Association ◽

10.33584/jnzg.2007.69.2680 ◽

2007 ◽

pp. 17-22

Author(s):

H. Lilienthal ◽

A. Brauer ◽

K. Betteridge ◽

E. Schnug

Keyword(s):

Remote Sensing ◽

Water Quality ◽

Land Use ◽

Land Use Change ◽

Satellite Remote Sensing ◽

Remote Sensing Data ◽

Native Vegetation ◽

Lake Water Quality ◽

Livestock Farming ◽

Slow Decline

Conversion of native vegetation into farmed grassland in the Lake Taupo catchment commenced in the late 1950s. The lake's iconic value is being threatened by the slow decline in lake water quality that has become apparent since the 1970s. Keywords: satellite remote sensing, nitrate leaching, land use change, livestock farming, land management

Download Full-text