PhD student, James Cook University
Quantifying rate of soil erosion, its effects and how it changes the landscape.
Soil erosion is a big environmental problem because erosion leads to soil loss, especially the most fertile top soil, which eventually results in loss of productivity of soil.My research aims at measuring how fast or slow soil is eroding, both by human interference, and naturally, so that we can do something to stop/prevent it. Without knowing how fast or slow is the erosion rate, proper actions cannot be put in place. Soil erosion also changes shape and looks of our landscape, and my research aims to understand at what rate is this change occurring, so that we can be prepared for the changes. My research helps in predicting what part of landscape will transform, which can be used to manage land-use for agriculture, settlement, and reforestation etc. My research will also help conservation agencies and policy makers in making effective policies to conserve and restore biodiversity affected by soil erosion, by providing them a quantified estimate of soil erosion. This will help them in understand the extent of damage and act accordingly.
Abstract: We analyze the source-to-sink variations of in situ10Be, 26Al and 21Ne concentrations in modern sediment of the Po river catchment, from Alpine, Apennine, floodplain, and delta samples, in order to investigate how the cosmogenic record of orogenic erosion is transmitted across a fast-subsiding foreland basin. The in situ10Be concentrations in the analyzed samples range from ∼0.8×104 at/gQTZ∼0.8×104 at/gQTZ to ∼6.5×104 at/gQTZ∼6.5×104 at/gQTZ. The 10Be-derived denudation rates range from 0.1 to 1.5 mm/yr in the Alpine source areas and from 0.3 to 0.5 mm/yr in the Apenninic source areas. The highest 10Be-derived denudation rates are found in the western Central Alps (1.5 mm/yr). From these data, we constrain a sediment flux leaving the Alpine and the Apenninic source areas (>27 Mt/yr and ca. 5 Mt/yr, respectively) that is notably higher than the estimates of sediment export provided by gauging (∼10 Mt/yr at the Po delta).
Pub.: 08 Aug '16, Pinned: 31 Jul '17
Abstract: The stream power law, expressed as E = KAmSn — where E is erosion rate [LT − 1], K is an erodibility coefficient [T − 1L (1 − 2m)], A is drainage area [L 2], S is channel gradient [L/L], and m and n are constants — is the most widely used model for bedrock channel incision. Despite its simplicity and limitations, the model has proved useful for topographic evolution, knickpoint migration, palaeotopography reconstruction, and the determination of rock uplift patterns and rates. However, the unknown parameters K, m, and n are often fixed arbitrarily or are based on assumptions about the physics of the erosion processes that are not always valid, which considerably limits the use and interpretation of the model. In this study, we compile a unique global data set of published basin-averaged erosion rates that use detrital cosmogenic 10Be. These data (N = 1457) enable values for fundamental river properties to be empirically constrained, often for the first time, such as the concavity of the river profile (m/n ratio or concavity index), the link between channel slope and erosion rate (slope exponent n), and substrate erodibility (K). These three parameters are calculated for 59 geographic areas using the integral method of channel profile analysis and allow for a global scale analysis in terms of climatic, tectonic, and environmental settings. In order to compare multiple sites, we also normalise n and K using a reference concavity index m/n = 0.5. A multiple regression analysis demonstrates that intuitive or previously demonstrated local-scale trends, such as the correlation between K and precipitation rates, do not appear at a global scale. Our results suggest that the slope exponent is generally > 1, meaning that the relationship between erosion rate and the channel gradient is nonlinear and thus support the hypothesis that incision is a threshold controlled process. This result questions the validity of many regional interpretations of climate and/or tectonics where the unity of n is routinely assumed.
Pub.: 04 Jun '16, Pinned: 31 Jul '17
Abstract: Global biogeochemical cycles have, as a central component, estimates of physical and chemical erosion rates. These erosion rates are becoming better quantified by the development of a global database of cosmogenic radionuclide 10Be (CRN) analyses of soil, sediment, and outcrops. Here we report the denudation rates for two small catchments (~ 0.9 km2) in the Mt. Lofty Ranges of South Australia as determined from 10Be concentrations from quartz sand from the following landscape elements: 1) dissected plateaux, or summit surfaces (14.10 ± 1.61 t km− 2 y− 1), 2) sandstone outcrops (15.37 ± 1.32 t km− 2 y− 1), 3) zero-order drainages (27.70 ± 1.42 t km− 2 y− 1), and 4) stream sediment which reflect a mix of landscape elements (19.80 ± 1.01 t km− 2 y− 1). Thus, the more slowly eroding plateaux and ridges, when juxtaposed with the more rapidly eroding side-slopes, are leading to increased relief in this landscape.
Pub.: 11 Jul '16, Pinned: 31 Jul '17
Abstract: Erosion rates of tropical landscapes are poorly known. Using measurements of in situ-produced 10Be in quartz extracted from river and landslide sediment samples, we calculate long-term erosion rates for many physiographic regions of Panama. We collected river sediment samples from a wide variety of watersheds (n = 35), and then quantified 24 landscape-scale variables (physiographic, climatic, seismic, geologic, and land-use proxies) for each watershed before determining the relationship between these variables and long-term erosion rates using linear regression, multiple regression, and analysis of variance (ANOVA). We also used grain-size-specific 10Be analysis to infer the effect of landslides on the concentration of 10Be in fluvial sediment and thus on erosion rates.
Pub.: 08 May '16, Pinned: 31 Jul '17
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