Examining the suitability of the geomorphic parameters in generating the Relative Index of Active Tectonics: an example from Himalayan Frontal Thrust, India

<p>This work emphasizes the efficient use of geomorphic parameters to form a unified index ~ Relative Index of Active Tectonics (RIAT), which has seldom been tested in areas with broader variability in the rate of deformation. This study aims to verify whether the geomorphic parameters can be used efficiently for RIAT to assess the spatial variability in deformation along the fault. The Himalayan Frontal Thrust has been chosen for morphotectonic evaluation owing to its active interplate thrust fault setting. For this purpose, we select vertical uplift sensitive geomorphic parameters viz., Mountain front sinuosity (S<sub>mf</sub>), Valley floor width-height ratio (V<sub>f</sub>), and Steepness index (K<sub>sn</sub>), as a primary tool to test the RIAT.</p><p>The result of RIAT shows the along-strike variation in response to the varying degree of deformation along the HFT. This is in fine agreement with the available long-term uplift/shortening rates and geodetic rates. Overall examination reveals RIAT being an excellent tool to assess the spatial variability in uplift rates in large tectonically active regions. However, the detailed scrutiny of individual geomorphic parameters reveals that only V<sub>f, </sub>and the K<sub>sn</sub> index are more responsive and go hand-in-hand with the RIAT variation. Whereas, S<sub>mf</sub> shows no spatial variation and function as least sensitive to such an investigation. The sensitivity of these individual parameters has implications for studies with similar settings elsewhere when quantitative rates are absent.</p>

Morphometric analysis of river subwatersheds using geographic information system and principal component analysis, northeast of Algeria

In the present paper an attempt is made to study the morphometric characteristics of five watersheds which are part of Seybouse and Coastal basin of Constantine located in northeast of Algeria. The study focuses on evaluating the effect of morphometric parameters on land degradation. The Geographical Information Systems which represent efficient tools in determination of drainage basin morphometric properties and principal component analysis are applied to ten geomorphic parameters on twenty subwatersheds, to group the parameters under different components based on significant correlations. Some morphometric parameters are computed and analyzed such as basin area, drainage density, stream frequency, form factor, orographic coefficient, hypsometric integral, and lithology index, basin slope, average overland flow distance, basin relief ratio. Outcomes of the matrix of correlation and principal component analysis of ten geomorphic parameters clearly depict that fifty percent of the variables are strongly correlated with the components like basin area, drainage density, stream frequency, orographic coefficient and relief ratio. It has been found that Guis sub-basin, three sub-basins of the Saf Saf watershed and all the sub-basins of the Mellah watershed are subjected to high land degradation, thus, creating an urgent need for applying soil and water conservation measures.

Use of geomorphic, hydrologic, and nitrogen mass balance data to model ecosystem nitrate retention in tidal freshwater wetlands

Geomorphic characteristics have been used as scaling parameters to predict water and other fluxes in many systems. In this study, we combined geomorphic analysis with in-situ mass balance studies of nitrate retention (NR) to evaluate which geomorphic scaling parameters best predicted NR in a tidal freshwater wetland ecosystem. Geomorphic characteristics were measured for 267 individual marshes that constitute the freshwater tidal wetland ecosystem of the Patuxent River, Maryland. Nitrate retention was determined from mass balance measurements conducted at the inlets of marshes of varying size (671, 5705, and 536 873 m2) over a period of several years. Mass balance measurements indicate that NR is proportional to total water flux over the tidal cycle. Relationships between estimated tidal prism (calculated water volume) for spring tides and various geomorphic parameters (marsh area, total channel length, and inlet width) were defined using measurements from air photos and compared to field data. From these data, NR equations were determined for each geomorphic parameter, and used to estimate NR for all marshes in the ecosystem for a reference spring (high) tide. The resulting ecosystem NR estimates were evaluated for (a) accuracy and completeness of geomorphic data, (b) relationship between the geomorphic parameters and hydrologic flux, and (c) the ability to adapt the geomorphic parameter to varying tidal conditions. This analysis indicated that inlet width data were the most complete and provided the best estimate of ecosystem nitrate retention. Predictions based on marsh area were significantly lower than the inlet width-based predictions. Cumulative probability distributions of nitrate retention indicate that the largest 3–4% of the marshes retained half of the total nitrate for the ecosystem.

Use of geomorphic, hydrologic, and nitrogen mass balance data to model ecosystem nitrate retention in tidal freshwater wetlands

Geomorphic characteristics have been used as scaling parameters to predict water and other fluxes in many systems. In this study, we combined geomorphic analysis with in-situ mass balance studies of nitrate retention (NR) to evaluate which geomorphic scaling parameters best predicted NR in a tidal freshwater wetland ecosystem. Geomorphic characteristics were measured for 267 individual marshes that constitute the freshwater tidal wetland ecosystem of the Patuxent River, Maryland. Nitrate retention was determined from mass balance measurements conducted at the inlets of marshes of varying size (671, 5705, and 536 873 m2) over a period of several years. Mass balance measurements indicate that NR is proportional to total water flux over the tidal cycle. Relationships between estimated tidal prism (total water volume) for spring tides and various geomorphic parameters (marsh area, total channel length, and inlet width) were defined and compared to field data. From these data, NR equations were determined for each geomorphic parameter, and used to estimate NR for all marshes in the ecosystem for a reference spring (high) tide. The resulting ecosystem NR estimates were evaluated for: (a) accuracy and completeness of geomorphic data, (b) relationship between the geomorphic parameters and hydrologic flux, and (c) the ability to adapt the geomorphic parameter to varying tidal conditions. This analysis indicated that inlet width data were the most complete and provided the best estimate of ecosystem nitrate retention. Predictions based on marsh area were significantly lower than the inlet width-based predictions. Cumulative probability distributions of nitrate retention indicate that the largest 3–4 % of the marshes retained half of the total nitrate for the ecosystem.