of Coastal Georgia Ecosystem Stressors using GIS Integrated Remotely Sensed
Imagery and Modeling: A Pilot Study for the Lower Altamaha River Basin
Mustafa M. Aral (School of Civil & Environmental Engineering, Georgia
Institute of Technology, Atlanta, GA, USA)
Georgia Sea Grant
College Program and the School of Civil & Environmental Engineering (Georgia
Institute of Technology)
The focus of this project is the development of the state-of-art methods to
analyze and evaluate the hydrologic and hydrogeologic characteristics of watersheds.
The Lower Altamaha River Basin in south Georgia was selected as the pilot study
area. The objective is to develop GIS-integrated watershed modeling software
for the basin.
are referred to the excellent website for this project:
from final report (see below):
this study, a hybrid surface/subsurface flow and transport model is developed
that blends the powerful distributed parameter models with relatively simpler
lumped parameter models. The proposed hybrid model solves the channel flow and
saturated groundwater flow domains in continuous time using fully distributed
physics-based formulations. This system is supported with the overland flow
and unsaturated groundwater flow that uses lumped parameter descriptions in
discrete time. This hybrid formulation decreases the computational requirements
associated with overland and unsaturated zone domains in a large scale continuous
watershed modeling task but still allows a representative description of the
watershed flow processes.
In the proposed model, a one-dimensional
channel flow model is dynamically coupled with a two-dimensional vertically-averaged
groundwater flow model along the river bed. As an alternative to the commonly
applied iterative solution technique, a so-called simultaneous solution procedure
is developed to provide a better understanding to the coupled flow problem.
This new methodology is based on the principle of solving the two flow domains
within a single matrix structure in a simultaneous manner. The method eliminates
the iterative scheme that is otherwise required to obtain the convergence of
the solution and provides a faster solution.
In addition to the flow model,
a coupled contaminant transport model is also developed to simulate the migration
of contaminants between surface and subsurface domains. Based on its flow counterpart,
the contaminant transport model dynamically couples a onedimensional channel
transport model with a two-dimensional vertically-averaged groundwater transport
model. The coupling is performed at the river bed interface via advective and
dispersive transport mechanisms. A modified extension of the proposed simultaneous
solution procedure is also implemented to solve the coupled contaminant transport
problem. The dynamic coupling provides the much needed understanding for the
continuity of contaminants in strongly interacting surface/subsurface systems
such as a river and an unconfined aquifer.
The coupled flow and transport
models are finally applied to the lower Altamaha watershed in southern Georgia.
The flow model is used to perform simulations of hydrologic and hydraulic conditions
along the river and in the dynamically linked surfacial aquifer. The model predicted
the flood patterns including the magnitude of peaks and their arrival times
with sufficient accuracy. Under the given flow conditions, the transport model
is then implemented to test alternative contaminant transport patterns both
in the river and within the aquifer."
March 2004 final report for
Georgia Sea Grant is especially detailed. This is a large PDF.
Surface and Subsurface
Flow and Contaminant Transport Modeling in the Lower Altamaha Watershed
Orhan Gunduz and
Mustafa M. Aral