scholarly journals Controls on eroded rock volume, a proxy for river incision, in Africa

Geology ◽  
2020 ◽  
Author(s):  
Jonathan D. Paul
Keyword(s):  
Drainage Basin ◽  
Gravity Anomalies ◽  
Rain Gauge ◽  
Vertical Surface ◽  
Drainage Patterns ◽  
River Incision ◽  
Basin Geometry ◽  
The Difference ◽  
Uplift And Erosion ◽  
Basin Area

A database of 3023 river basins in Africa was assembled to investigate the relative effects of uplift and erosion on landscape development. The volume of rock eroded from each basin was calculated by integrating the difference between a topographic summit envelope fit across drainage divides and interfluves, and present-day topography over basin area. Africa is an excellent natural laboratory for this procedure because drainage patterns reflect the Neogene development of topographic basins and swells, themselves surficial manifestations of sub-lithospheric mantle convection. As a result, the loci of major offshore deltas and drainage divides have remained largely static, while epeirogenic (vertical) surface motions are more important than shortening. Eroded rock volume is presented as a proxy for fluvial incision and correlates strongly with long-wavelength gravity anomalies across Africa, but not with mean precipitation, which was calculated by merging satellite estimates with rain gauge data. This finding implies that spatial variations in epeirogenic uplift govern landscape evolution across the continent. Other variables that alter drainage basin geometry and the magnitude of eroded rock volumes, such as varying climate, bedrock erodibility, and drainage capture, are likely subordinate to these variations. First-order estimates of eroded rock volume onshore are potentially the most accurate indicator of offshore sedimentation because they implicitly include information pertaining to basin area and relief, which together control sediment load.

scholarly journals Μορφοτεκτονική μελέτη της ευρύτερης περιοχής Θεσ/νίκης για τη χαρτογράφηση νεοτεκτονικών ρηγμάτων.

2005 ◽  
Vol 38 ◽  
pp. 30 ◽  
Author(s):  
Α. ΖΕΡΒΟΠΟΥΛΟΥ ◽  
Σ. ΠΑΥΛΙΔΗΣ
Keyword(s):  
Drainage Basin ◽  
Digital Elevation Models ◽  
Active Faults ◽  
Gradient Index ◽  
Stream Length ◽  
Drainage Patterns ◽  
Digital Elevation ◽  
Mountain Front ◽  
Morphotectonic Indices

At this paper studied the neotectonic active faults of the broader area of Thessaloniki with morphotectonic criteria. We have studied three main faults of Anthemounta, Asvestophori and Pylaia - Panorama with the contribution of cartography, digital elevation models, drainage patterns, and the morphotectonic indices like drainage basin asymmetry, mountain front sinuosity, knick points and stream length-gradient index. Those faults show elements of activity.

scholarly journals A Comparison Between Global Satellite Mapping of Precipitation Data and High-Resolution Radar Data – A Case Study of Localized Torrential Rainfall over Japan

2021 ◽  
Vol 16 (4) ◽  
pp. 786-793
Author(s):  
Yoshiaki Hayashi ◽  
Taichi Tebakari ◽  
Akihiro Hashimoto ◽  
◽  
Keyword(s):  
High Resolution ◽  
Heavy Rainfall ◽  
Daily Rainfall ◽  
Radar Data ◽  
Rain Gauge ◽  
Hourly Rainfall ◽  
The Difference ◽  
Microwave Imager ◽  
Satellite Mapping

This paper presents a case study comparing the latest algorithm version of Global Satellite Mapping of Precipitation (GSMaP) data with C-band and X-band Multi-Parameter (MP) radar as high-resolution rainfall data in terms of localized heavy rainfall events. The study also obliged us to clarify the spatial and temporal resolution of GSMaP data using high-accuracy ground-based radar, and evaluate the performance and reporting frequency of GSMaP satellites. The GSMaP_Gauge_RNL data with less than 70 mm/day of daily rainfall was similar to the data of both radars, but the GSMaP_Gauge_RNL data with over 70 mm/day of daily rainfall was not, and the calibration by rain-gauge data was poor. Furthermore, both direct/indirect observations by the Global Precipitation Measurement/Microwave Imager (GPM/GMI) and the frequency thereof (once or twice) significantly affected the difference between GPM/GMI data and C-band radar data when the daily rainfall was less than 70 mm/day and the hourly rainfall was less than 20 mm/h. Therefore, it is difficult for GSMaP_Gauge to accurately estimate localized heavy rainfall with high-density particle precipitation.

How HY-2A/GM altimeter performs in marine gravity derivation: assessment in the South China Sea

2019 ◽  
Vol 219 (2) ◽  
pp. 1056-1064 ◽  
Author(s):  
Chengcheng Zhu ◽  
Jinyun Guo ◽  
Cheinway Hwang ◽  
Jinyao Gao ◽  
Jiajia Yuan ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
Gravity Anomalies ◽  
The South China Sea ◽  
The South ◽  
China Sea ◽  
Open Sea ◽  
Marine Gravity ◽  
Sea Surface Heights ◽  
The Difference

SUMMARY HY-2A is China's first satellite altimeter mission, launched in Aug. 2011. Its geodetic mission (GM) started from 2016 March 30 till present, collecting sea surface heights for about five 168-d cycles. To test how the HY-2A altimeter performs in marine gravity derivation, we use the least-squares collocation method to determine marine gravity anomalies on 1′ × 1′ grids around the South China Sea (covering 0°–30°N, 105°E–125°E) from the HY-2A/GM-measured geoid gradients. We assess the qualities of the HY-2A/GM-derived gravity over different depths and areas using the bias and tilt-adjusted ship-borne gravity anomalies from the U.S. National Centers for Environmental Information (NCEI) and the Second Institute of Oceanography, Ministry of Natural Resources (MNR) of P. R. China. The RMS difference between the HY-2A/GM-derived and the NCEI ship-borne gravity is 5.91 mGal, and is 5.33 mGal when replacing the HY-2A value from the Scripps Institution of Oceanography (SIO) V23.1 value. The RMS difference between the HY-2A/GM-derived and the MNR ship-borne gravity is 2.90 mGal, and is 2.76 mGal when replacing the HY-2A value from the SIO V23.1 value. The RMS difference between the HY-2A and SIO V23.1 value is 3.57 mGal in open sea areas at least 20 km far away from the coast. In general, the difference between the HY-2A/GM-derived gravity and ship-borne gravity decreases with decreasing gravity field roughness and increasing depth. HY-2A results in the lowest gravity accuracy in areas with islands or reefs. Our assessment result suggests that HY-2A can compete with other Ku-band altimeter missions in marine gravity derivation.

scholarly journals Concentrations and Loads of Dissolved and Particulate Organic Carbon in Urban Stormwater Runoff

Water ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 1031 ◽  
Author(s):  
Stefan Kalev ◽  
Gurpal S. Toor
Keyword(s):  
Organic Carbon ◽  
Stormwater Runoff ◽  
Light Availability ◽  
Rain Gauge ◽  
Urban Landscapes ◽  
Storm Events ◽  
Wet Season ◽  
The Difference ◽  
Urban Stormwater Runoff ◽  
High Concentrations

Urban landscapes are significant contributors of organic carbon (OC) in receiving waters, where elevated levels of OC limit the light availability, increase the transport of pollutants, and result in high costs of potable water treatment. Our objective in this study was to investigate the concentrations, fractions (dissolved and particulate), and loads of OC in a residential catchment (3.89 ha drainage area) located in Florida, United States. The outlet of the stormwater pipe draining the residential catchment was instrumented with an automated sampler, a flowmeter, and a rain gauge. The rainfall and runoff samples collected over 25 storm events during the 2016 wet season (June to September) were analyzed for dissolved organic carbon (DOC) and total organic carbon (TOC), with particulate OC (POC) calculated as the difference between TOC and DOC. Mean concentration of DOC was 2.3 ± 1.7 mg L−1 and POC was 0.3 ± 0.3 mg L−1 in the rainfall, whereas DOC was 10.5 ± 6.20 mg L−1 and POC was 2.00 ± 4.05 mg L−1 in the stormwater runoff. Concentrations of DOC were higher during the rising limb of the hydrograph in 15 out of 25 storm events, suggesting flushing of DOC, with an increase in the amount of runoff, from the landscape sources in the residential catchment. The estimated total export of OC during the 2016 wet season was 66.0 kg ha−1, of which DOC was 56.9 kg ha−1 (86.2% of TOC), and POC was 9.1 kg ha−1 (13.8% of TOC). High concentrations and loads of OC, especially DOC, in the stormwater runoff imply that residential catchments in urban watersheds are hot-spots of DOC influx to water bodies. Reducing DOC transport in the urban landscapes is complex and require identifying the origin of DOC and then using site-specific targeted approaches to mitigate DOC loss.

scholarly journals Use of Remote-Sensing Data in Modelling Run-Off from the Greenland Ice Sheet

1987 ◽  
Vol 9 ◽  
pp. 215-217 ◽  
Author(s):  
H.H. Thomsen ◽  
R.J. Braithwaite
Keyword(s):  
Drainage Basin ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Remote Sensing Data ◽  
Landsat Data ◽  
Local Surface ◽  
Drainage Patterns ◽  
Lack Of Information ◽  
Run Off ◽  
Subglacial Topography

Run-off modelling is needed in Greenland to extend the short series of measurements. However, the delineation of hydrological basins on the Greenland ice sheet is difficult because of the lack of information about surface and subglacial drainage patterns. Low Sun-angle Landsat data have been used for mapping local surface features which has led to an improvement in basin delineations and thereby run-off simulations. Work is now in progress to map subglacial topography by electromagnetic reflection (EMR) from a helicopter. This information will be used for calculating hydraulic potentials within the basin and to assess the possibilities of future changes in drainage-basin delineation.

scholarly journals On the topographic effects by Stokes’ formula

2014 ◽  
Vol 4 (1) ◽  
Author(s):  
L.E. Sjöberg
Keyword(s):  
Gravity Anomaly ◽  
Bouguer Anomaly ◽  
Gravity Anomalies ◽  
Geoid Height ◽  
Topographic Effects ◽  
Gravimetric Geoid ◽  
Bouguer Gravity ◽  
The Third ◽  
Stokes Formula ◽  
The Difference

AbstractTraditional gravimetric geoid determination relies on Stokes’ formula with removal and restoration of the topographic effects. It is shown that this solution is in error of the order of the quasigeoid-to-geoid difference, which is mainly due to incomplete downward continuation (dwc) of gravity from the Earth’s surface to the geoid. A slightly improved estimator, based on the surface Bouguer gravity anomaly, is also biased due to the imperfect harmonic dwc the Bouguer anomaly. Only the third estimator,which uses the (harmonic) surface no-topography gravity anomaly, is consistent with the boundary condition and Stokes’ formula, providing a theoretically correct geoid height. The difference between the Bouguer and no-topography gravity anomalies (on the geoid or in space) is the “secondary indirect topographic effect”, which is a necessary correction in removing all topographic signals.

scholarly journals River profile response to normal fault growth and linkage: An example from the Hellenic forearc of south-central Crete, Greece

2016 ◽  
Author(s):  
Sean F. Gallen ◽  
Karl W. Wegmann
Keyword(s):  
Drainage Basin ◽  
Profile Analysis ◽  
Normal Fault ◽  
Drainage Area ◽  
Fault System ◽  
Stream Power ◽  
River Incision ◽  
South Central ◽  
History Of ◽  
Fault Growth

Abstract. Topography is a reflection of the tectonic and geodynamic processes that act to uplift the Earth's surface and the erosional processes that work to return it to base level. Numerous studies have shown that topography is a sensitive recorder or tectonic signals. A quasi-physical understanding of the relationship between river incision and rock uplift has made the analysis of fluvial topography a popular technique for deciphering relative, and some argue absolute, histories of rock uplift. Here we present results from a study of the fluvial topography from south-central Crete demonstrating that river longitudinal profiles indeed record the relative history of uplift, but several other processes make it difficult to recover quantitative uplift histories. Prior research demonstrates that the south-central coastline of Crete is bound by a large (~100 km long) E-W striking composite normal fault system. Marine terraces reveal that it is uplifting between 0.1–1.0 mm yr−1. These studies suggest that two normal fault systems, the offshore Ptolemy and onshore South-Central Crete faults linked together in the recent geologic past (Ca. 0.4–1 Myrs bp). Fault mechanics predicts that when adjacent faults link into a single fault the uplift rate in the linkage zone will increase rapidly. Using river profile analysis we show that rivers in south-central Crete record the relative uplift history of fault growth and linkage, as theory predicts that they should. Calibration of the commonly used stream power incision model shows that the slope exponent, n, is ~ 0.5, contrary to most studies that find n ≥ 1. Analysis of fluvial knickpoints shows that migration distances are not proportional to upstream contributing drainage area, as predicted by the stream power incision model. Maps of the transformed stream distance variable, χ, indicate that drainage basin instability, drainage divide migration and river capture events complicate river profile analysis in south-central Crete. Waterfalls are observed in southern Crete and appear to operate under less efficient and different incision mechanics than assumed by the stream power incision model. Drainage area exchange and waterfall formation are argued to obscure linkages between empirically derived metrics and quasi-physical descriptions of river incision, making is difficult to quantitatively interpret rock uplift histories from river profiles in this setting. Karst hydrology, break down of assumed drainage area-discharge scaling and chemical weathering might also contribute to the failure of the stream power incision model to adequately predict the behavior of the fluvial system in south-central Crete.

The calculation of deflexions of the vertical from gravity anomalies

1950 ◽  
Vol 204 (1078) ◽  
pp. 374-395 ◽  
Keyword(s):  
Gravity Data ◽  
Gravity Anomalies ◽  
Sources Of Error ◽  
Free Air ◽  
Gravity Measurements ◽  
Standard Deviations ◽  
The Difference ◽  
Different Sources

The theory of the application of gravity measurements to geodetic calculations is discussed, and the errors involved in calculating deflexions of the vertical are estimated. If the gravity data are given as free air anomalies from Jeffreys’s (1948) formula, so thdt the second and third harmonics of gravity are assumed known, the orders of magnitude of the standard deviations of the different sources of error are the following: Single deflexion: neglect of gravity outside 20° 1" Difference of deflexions: neglect of gravity outside 5° 0"·5 Calculation of effects of gravity from 0º·05 to 5° 0"·1 Calculation of effects of gravity within 0º·05 between 0"·1 and 0"·5 Estimates of the deflexions are made for Greenwich, Herstmonceux, Southampton and Bayeux, and the difference between Greenwich and Southampton is compared with the astronomical and geodetic amplitudes.

The Bengal Fan sediment archive: a record of Himalayan tectonics, climate, and/or drainage routing change between source and sink?

2020 ◽  
Author(s):  
Yani Najman ◽  
Mike Blum ◽  
Jamie Gleason ◽  
Kimberly Rogers ◽  
Devon Orme ◽  
...  
Keyword(s):  
Drainage Basin ◽  
Foreland Basin ◽  
Deep Ocean ◽  
Detrital Zircons ◽  
Bengal Fan ◽  
Zircon Fission Track ◽  
Major Increase ◽  
The Difference ◽  
Hf Isotopic Composition ◽  
Himalayan Tectonics

<p>The Bengal Fan IODP Exp 354 core provides a Neogene re­cord of eastern and central Himalayan exhu­mation. U-Pb analyses of detrital zircons from this sediment archive shows that from ~ 4 Ma, there was a major increase in grains aged <300 Ma, indicating a major increase in contribution from the Trans-Himalaya (Blum et al., Nature SR, 2018). Detrital rutile U-Pb and detrital zircon fission track data from the same archive (Najman et al, GSAB 2019) indicates an approximately coeval increase in exhumation rate from the Eastern Himalayan Syntaxis. Thus an attractive explanation to explain the increase in Transhimalayan input may be that it was caused by initiation of exhumation of the syntaxis from beneath its Transhimalayan cover. However, a similar dataset obtained from the proximal foreland basin Siwalik deposits (Govin et al., in review) indicates an earlier onset to syntaxial exhumation, compared to that recorded in the distal sediment archive. We consider therefore whether climate change may be responsible for the increased Transhimalayan input: onset of Northern Hemisphere glaciation may have increased the proportion of erosion in the higher, glaciated, regions of the Transhimalaya, compared to that part of the orogen south of the suture zone. Analyses of Hf isotopic composition of detrital zircons to assess the possibility that drainage basin changes may explain the increase in material at 4 Ma, are ongoing. The difference in timing of the syntaxial exhumational signal between the proximal and distal archives may be the result of downstream dilution, or may result from sequestration of material on the shelf, with release to the deep ocean during sea level low stands.</p>

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