A pinboard by
Ashish Mishra

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.


Global analysis of the stream power law parameters based on worldwide 10Be denudation rates

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