The document summarizes work to model the highly modified flow network of the Guadalupe River Delta through field data collection and hydrodynamic modeling. Key points: 1) Field work was conducted to collect bathymetry data and map the complex channel network altered by diversions and restrictions using lidar and channel extraction tools. 2) A high-resolution hydrodynamic model called Frehd will be used to understand current conditions and inform management, representing features as boundary conditions on a 10m grid coarsened from lidar. 3) Sensors have been installed throughout the system to monitor inputs, outputs, and junctions to verify the Frehd model, which will focus on recovering this field-collected data.

1. Deciphering the highly-modified flow paths through the Guadalupe River bayous
Richard A. Carothers1
, Paola Passalacqua1
, Ben R. Hodges1
1-Center for Research in Water Resources, Environmental and Water Resources Engineering,
Department of Civil, Architectural and Environmental Engineering, The University of Texas at Austin
(richardcarothersUT@gmail.com, paola@austin.utexas.edu, hodges@mail.utexas.edu)
Field work for model verification
Bathymetry
Digitizing water channels
Flow network,diversions,restrictions
Overview
This work is funded by TWDB account 1400011710.The authors would thank the TWDB for the funding and provided data.Likewise,thanks go out to the
GBRA for data,field consultation,and land access.The authors would also like to thank D.Alonso,G.Colville,D.Williams,and K.Kriegel for field consultation
and land access.Finally,thanks to C.Van Dyk for field help with data collection.
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• The flow network seen in the central
map is based on a modified NHD data-
set.
• Diversions in the form of canals (seen
as red flowlines on the central map)
divert fresh water from the Guadalupe
River for industrial use east of the Victo-
ria Barge Canal.
• Restrictions such as the Guadalupe
Blanco River Authority (GBRA) salt barri-
er (Figure 2),salt barrier diversion gate,
and the Hog and Goff bayou salt gates
(circled in black and yellow on the cen-
tral map) prevent inland migration of
salt water and contamination of indus-
trial use water.
• Water surface extent poly-
gons removed from the DEM
and replaced by bathymetry.
• Bathymetric surveys per-
formed by the GBRA along
the lower Guadalupe and the
series of diversion canals pro-
vide some in-channel ba-
thymetry.Mission Lake ba-
thymetry provided by the
Texas Water Development
Board (TWDB).
5
Moving forward with the Frehd Model
• Frehd model developed by Dr.Ben
R.Hodges at the Center for Research
in Water Resources at the University
of Texas at Austin and used previous-
ly to model the fluxes through the
Nueces Deltad
• 2D or 3D model capable of solving
the shallow water equations simulat-
ing water and salt flux over a roughly
10m scale Cartesian grid mesh.
• Restrictions,sinks,and smaller fea-
tures are sub-modeled as boundary
conditions along cell edges.
• Continuing work will focus on re-
covering installed field sensors and
verifying the Frehd model with re-
covered data.
• A series of field work excursions installed barometers,levelog-
gers,and conductivity temperature depth sensors throughout
the system (Figure 5.1).
• Sytem inputs,output,and major junctions were selected for
monitoring.
• Current sensor installed as represented by circles with points on
central map while upcoming sensor installation locations seen as
spoked circles in central map.
Figure 3.1 (right) -
(a) Water hyacinth
covering a diver-
sion canal at time
of lidar data collec-
tion,01/2013.(b)
Same water course
in 11/2014 after
spraying the hya-
cinth with herbi-
cide.
Figure 1 - The
Guadalupe
River Delta is
located along
the Texas Gulf
Coast about
30 miles
southeast of
Victoria,TX.
Figure 2 - The GBRA salt barrier is composed of two inflatable fabric bladders seen
beneath the water in the left image.During periods of low flow in the river,the
bladders are inflated raising the backwater elevation of the river and preventing
salt migration upstream.
Figure 5.1 - Sensors
were mounted atop a
rod with a concrete
base and submerged in
the waterways.A rope
attached by u-bolt se-
cured them to the
bank.
Acknowledgements
References
• Artificial channelization and flow restrictions on the lower
Guadalupe River Delta along the Texas Gulf Coast (Figure 1)
have altered the natural flow network through its surrounding
bayou and estuary system leading to marked ecosystem degra-
dation.
• A“drained”lidar DEM is prepared by removing water features
from the dataset and replacing them with bathymetry.Semi-au-
tomated channel extraction features are developed facilitating
feature removal.
• The fine resolution environmental hydrodynamic model (Freh-
da
) is used to facilitate understanding of the current in-situ con-
ditions and provide a tool for informed decision making.
Figure 4 -“Drained”DEM showing
bathymetry combined with lidar
based topography
Figure 5.2 - A field hand stands watch along the western shore of Schwings bayou.
0 100 200 300 400
Meters
a) Information available at http://www.crwr.utexas.edu/hodges/frehd.html
b) Passalacqua,P.,T.D.Trung,E.Foufoula-Georgiou,& W.E.Dietrich.(2010a).A geometric
framework for channel network extraction from lidar:Nonlinear diffusion and geodesic
paths.Journal of Geophysical Research,115(F01002).doi:
10.1177/030913338000400204.(https://sites.google.com/site/geonethome/home)
c) Passalacqua,P.,P.Belmont,& E.Foufoula-Georgiou.(2012).Automatic geomorphic feature
extraction from lidar in flat and engineered landscapes.Water Resources Research,
48(W03528).doi:10.1029/2011WR010958.
d) Ryan,A.J.,Hodges,B.R.(2011).“Modeling hydrodynamic fluxes in the Nueces River delta.”,Center for Research in Water Resources,The University of
Texas at Austin.CRWR Online Report 11-07,92 pgs.
Figure 3.2 (left and
below) - (a)
Cross-sections are
struck along
stream centerlines
using the GeoNet
feature extraction
toolboxc
.(b) Bank
location points are
determined based
on surface slope
maxima along each
cross section.(c)
Bank points are
connected to form
a water polygon.
• Lidar uses the idea of radar but with pulses of light to
map topography at a very high resolution.This 1m reso-
lution DEM was obtained from the Texas Bureau of Eco-
nomic Geology and developed from lidar flown in Janu-
ary of 2013.
• Lidar returns“no data”for water surfaces resulting in
easily identifiable water courses,but an infestation of the
system by the invasive species water hyacinth masks the
water surface in the dataset making the digitizing of
water extents difficult (Figure 3.1).
• Using the GeoNetb
toolbox,a semi-automated process
was developed to approximate the water surface extents
where hyacinth is present (Figure 3.2).
Figure 6 - DEM from the Nueces Delta study coarsened from 1m2
to 15m2
pixel size for
use in the Frehd model
(a)
(b)
l(
l(
l(
l(
l(
l(
l(
(
(
(
(HH
H
H
H
H
H
H
HH
H
H
HH
H
p0 0.5 1
Kilometers
l(
l(
Guadalupe Delta Lidar
31.3 m
- 1.5 m
Modified NHD flowlines
Freshwater Diversion Canals
( Flow Restrictions
Current Sensor Locations
H 10m CTD
H 10m TD
H 5m TD
H Barometer
Future Sensor Locations
l( 5m TD
l( 10m CTD
H
H
H
H
(a)
(b) (c)
High : 3 m
Low : -2 m
Salt Barrier Diversion Canal
Guadalupe San Antonio
River Confluence
Green Lake
Mission Lake
Highway 35 Diversion Canal
Traylor Cut
Hog Bayou
Mamie Bayou
Schwings Bayou
Upper Hog Bayou
Goff Bayou
Victoria Barge Canal
Guadalupe River
Hog Bayou Salt Gate
Goff Bayou Salt Gate
GBRA Salt Barrier
Salt Barrier Diversion Canal Gate
Guadalupe River North Fork
Guadalupe River South Fork