Harish Sangireddy

GeoNet: An open source software for the automatic and objective extraction of channel heads, channel network, and channel morphology from high resolution topography data

Abstract Extracting hydrologic and geomorphic features from high resolution topography data is a challenging and computationally demanding task. We illustrate the new capabilities and features of GeoNet, an open source software for the extraction of channel heads, channel networks, and channel morphology from high resolution topography data. The method has been further developed and includes a median filtering operation to remove roads in engineered landscapes and the calculation of hillslope lengths to inform the channel head identification procedure. The software is now available in both MATLAB and Python, allowing it to handle datasets larger than the ones previously analyzed. We present the workflow of GeoNet using three different test cases; natural high relief, engineered low relief, and urban landscapes. We analyze default and user-defined parameters, provide guidance on setting parameter values, and discuss the parameter effect on the extraction results. Metrics on computational time versus dataset size are also presented. We show the ability of GeoNet to objectively and accurately extract channel features in terrains of various characteristics.

Identifying environmental controls on the shoreline of a natural river delta

River deltas form where sediment-laden water debouches into a basin. The spatial delineation of a delta is nontrivial and yet is fundamental to systematically evaluating fluxes across its surface. Here we study shoreline dynamics of the Wax Lake Delta (WLD), a naturally developing delta, downstream of the Atchafalaya River, USA. We demonstrate the ability to extract hydrodynamic and morphodynamic shorelines from time series of satellite imagery and topography data, respectively. The hydrodynamic shoreline corresponds to the traditional dry-wet interface, whereas we introduce the concept of a morphodynamic shoreline demarcating the topset-foreset transition of a delta to quantitatively express the degree of inundation of a delta plain. These shorelines enable us to assess environmental controls on inundation of the WLD delta plain, noting the abundance of satellite imagery, whereas time series of bathymetric data from delta plains are scarce. From the analysis of NOAA and U.S. Geological Survey environmental data, we identify the effects of river discharge, tides, wind, and vegetation on shoreline position. In particular, using Delft3D simulations and a simplified momentum balance, we highlight the nonuniform and nonlinear effect of wind on delta plain inundation. Our analyses reveal that wind, riverine discharge, and tides significantly contribute to inundation of the WLD, and hence, incorporating their interaction is essential to the accurate modeling of hydrodynamics and ecodynamics of the WLD delta plain, as well as to the dynamic shape of delta plains in general.