Form SemiAnnl
(2/2006)
(GSD-EPC)
RTI
Semi-Annual Progress Report
Fiscal Year
Date of This Report: 31 August 2007
2007
Project Number: 0-4695
RMC: 3
Period Covered by This Report: 01 March 2007 – 31 August 2007
Project Title: Designs for Mitigation of Damage in Areas of High Bed-Mobility
Research Supervisor
Researcher
Researcher
Researcher
Name
Agency
Phone
Fax
Email
David Thompson
William Asquith
Xing Fang
Ted Cleveland
TechMRT
USGS
Lamar Univ.
Univ. of Houston
806-742-3485
512-927-3580
409-880-2287
713-743-4280
806-742-3449
512-927-3580
409-880-8121
713-743-4260
David.thompson@ttu.edu
wasquith@usgs.gov
Xing.Fang@lamar.edu
Cleveland@uh.edu
1. Requested Changes for Possible Project Modification
No modifications requested at this time. Project scheduled for termination in FY 2008.
2. Equipment
None.
3. Progress to Date, by Task
Task 1: Literature Review: Literature review is complete and published.
Task 2: Field Examinations: During the week of 12July04, team members visited three Johnson Fork
Creek crossings and Ben Williams crossing, where we took field samples of bed materials, field-sieved
samples, and made grid measurements of surface armoring. Results from the field visits have been
analyzed. Task 2 is complete.
Task 3: Qualitative Laboratory Modeling: University of Houston personnel fabricated and operated a
qualitative physical model. Results from field studies were used in establishing appropriate model size
and material size for modeling. The model was used to show that bed-mobility could be achieved in the
laboratory using field-scale materials. Additional physical model setup was completed and test runs will
begin during the second quarter of 2006. Task 3 is complete.
Task 4: Interim Report: The informal interim report is complete.
Task 5: Field Work: Field investigations have included geophysical mapping of gravel channel bars,
channel cross-sectional surveys, and sediment sampling by USGS personnel. GIS analyses concentrated
on characterizing channel slopes in the study area and organizing spatial and tabular data. Field
investigations and GIS analyses have been done to augment modeling efforts at the collaborating
universities. The primary objectives of the field and GIS work are to: (1) identify and quantify spatial
patterns of gravel-bed mobility in the study area and (2) measure and interpret variables that are
common to numerical and physical bedload models.
1 of 6
Form SemiAnnl
(2/2006)
Field investigations have been located in a 3-county study area in the Edwards Plateau, including
Edwards, Kimble, and Real counties. A number of river systems have their headwaters in this area,
including the Llano, Frio, and Nueces rivers, and Sycamore Creek. All river systems in the study area
transport considerable loads of gravel- and cobble-sized material. In early June, a trip was made to
characterize and map the shallow subsurface (~2 to 10 meters) sedimentary characteristics of
gravel/cobble bars using OhmMapper, a geophysical resistivity tool. Transects were made across large
gravel bars of the Nueces River at Ben Williams Crossing along FM 335 and Johnson Fork at Lowlands
Crossing along FM 2169. Preliminary processing of the collected data indicate considerable variability
in resistivity across transects and at depth, but transects that were observed to be highly variable at the
surface have discernable differences in the resistivity profiles. For example, surface water of the Nueces
River downstream from Ben Williams Crossing completely sinks into the gravel bar; resistivity profiles
across the channel show lower resistivity immediately downstream of the sink. This exercise will serve to
calibrate the physical and numerical models of the university collaborators.
Other field trips in June to November have been made to collect channel geometry and particle-size data
at selected reaches in the study area. Channel geometry is measured using total station surveying
techniques. Three or four cross-sections are surveyed at each selected reach. Particle-size of gravel and
cobble-sized material is measured through the use of a gravelometer template and a sampling grid.
Hundreds of individual gravels and cobbles are measured to generate particle-size distribution curves.
The results of total station surveys and sediment characterization of multiple channel cross-sections
along Johnson Fork, the South Llano River, and the North Llano River will provide parameters used in
numerical modeling of bed-material entrainment in the study area. The results will also be used to make
laboratory physical models more realistic and applicable.
The USGS completed fieldwork, data analysis, and interpretation of data associated with the project.
Task 5 is complete.
Task 6: Physical Modeling: Initial work on the physical model was completed late in 2005 with
extensions to that component during FY 2006 and FY 2007.
A temporary flume was designed and constructed at University of Houston. The bulk of that construction
was completed during the prior reporting period (ending 28 February 2007). Figure 1 is an image circa
February 2007. The instrumentation in-place for the smaller UH flume was moved to this new larger
flume and experiments resumed. The large flume was substantially completed March 2007. Experiments
are currently underway; Figures 2-4 are images from a recent experimental run illustrating solids
motion, deposition, and culvert clogging.
2 of 6
Form SemiAnnl
(2/2006)
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Figure 1. Large Flume near completion.
Figure 2. Solids moving at near critical
Froude number.
Figure 3. Culvert model before solids clogging,
Froude number is about 0.65.
3 of 6
Figure 4. Culver model after clogging;
Froude number is about 0.65
Form SemiAnnl
(2/2006)
Figure 5. Experimental Froude number history for experimental depicted in Figures 2-4.
Task 6 is essentially complete, although reduction of physical modeling experiments and analysis of
results remains to be completed.
Task 7: Numerical Modeling: Numerical Modeling: Two VBA programs have been developed: one is to
compute bed-load transport rate in a gravel-bedded river by using Gary's surface based transport
equation, and another is to compute channel flow parameters when discharge and channel geometry
(irregular shape) are given. These two programs are integrated in an Excel spreadsheet and allow
researchers and TxDOT engineers to compute bed-load transport rate in gravel-bedded natural
channels. A conference paper was presented in the Texas ASCE spring meeting to summarize the study
for the past two years. FLOW-3D has been identified to simulate flow conditions over a low-water
stream crossing. Researchers are working on some case studies of flow simulation and gravel transport
estimation in three low-water crossings at Johnson Fork river using FLOW-3D. Channel geometry data
from HEC-RAS and provided by TxDOT engineer have been converted into three-dimensional geometry
data for three flow simulations.
4 of 6
Form SemiAnnl
(2/2006)
Additional unsteady numerical modeling included application of HEC-RAS to Johnson Fork and the
three low-water crossings subjected to field study in 2004. Results will be used to drive a model of
sediment movement.
A manuscript entitled “Potential for Bed-Material Entrainment in Selected Streams of the Edwards
Plateau, Texas” was written, reviewed, and edited by USGS researchers. Currently, the manuscript is
being formatted for publication, possibly as a USGS Scientific Investigations Report (SIR). The report
summarizes the methods and analyses used to quantify bed-material entrainment in the study area.
Additionally, the Ph.D. dissertation topic of co-PI Frank Heitmuller (UT-Austin and USGS) is associated
with TxDOT project 0–4695. A summary of the findings is provided below.
The Texas Department of Transportation (TxDOT) experiences maintenance difficulties with low-water
crossings (LWCs) of streams in the Edwards Plateau in central Texas, as a result of the transport of
cobble- and gravel-sized bed material. TxDOT Research Project 0–4695 is tasked to research the bedmaterial entrainment phenomenon as related to LWC maintenance issues in the Edwards Plateau. The
bed-material entrainment problem for TxDOT LWCs occurs at two spatial scales. First, the relative
supply and abundance of cobble- and gravel-sized bed material at a location can be attributed to
watershed characteristics, specifically watershed slope. The relative supply and abundance of bed
material along a given channel reach becomes greater with increasingly steeper watershed slopes, based
on digital elevation model (DEM) analyses and qualitative observations made during fieldreconnaissance trips to the study area. Second, the stresses needed to mobilize bed material at a location
can be attributed to reach-scale hydraulic factors. The propensity for initial and complete entrainment of
bed material is dependent on cross-sectional geometry and particle size. Flood-frequency analyses are
associated with computations of bed-material entrainment to estimate the frequency of bed-material
entrainment. In general, the frequency of entrainment increases with downstream distance, as a result of
decreasing particle size and increased flood magnitudes. An average of 1 year occurs between flows that
initially entrain bed-material up to the median particle size (d50), and an average of 1.5 years occurs
between flows that completely entrain bed-material up to the median particle size (d50). The Froude
numbers (F), useful for design engineers, associated with initial and complete entrainment of bedmaterial up to the median particle size (d50) approximately are 0.40 and 0.45, respectively.UH
researchers examined the stability of the Llano watershed, in which the study area is located. Although
the modified universal soil loss equation (MUSLE) is generally applied to quantify suspended load, it is
an acceptable tool for a relative quantitative stability assessment of a large area like an entire
watershed. Data needed for the model are sub-watershed areas, runoff volumes, erodibility factors,
topographic factors, and land management coefficients. Those different variables were derived from 30meter DEMs, data from the high-resolution National Hydrography Dataset (NHD), rainfall hyetographs
from the National Climatic Data Center (NCDC), and the Texas surface geology map from the USGS.
ArcGIS 9.1 was used for data management and aerial analysis. A qualitative assessment shows that the
culverts under investigation are located in an area with a high susceptibility of erosion and sediment
yield. The quantitative assessment is being finalized.
The data mentioned above are also used for the study and modeling of the sediment movements at
Johnson Fork, which is on of the areas of interest. Channel cross-sections and land characteristics were
transferred from the GIS model to HEC-GeoRAS for steady and unsteady-flow simulations. Simulation
tests are running. A floodplain using the Nov-11 flood event has been mapped. Results will also be used
to drive a model of sediment movement.
4. Progress on Development of “Product” Deliverables
5 of 6
Form SemiAnnl
(2/2006)
Product #
Product Description
4695-1
Informal report
4695-2
Project report
4695-S
Summary report
Progress to Date & Implementation Status
Complete
None
None
5. Meetings/Conferences

No formal meetings were held. However, substantial informal discussions via email, telephone, and
during meeting associated with other projects occurred.
6. Possible Candidates for Formal Presentations at the Upcoming RMC Meeting
Project research work is essentially complete. Modeling continues at UH through the end of the
reporting period. Resources for FY 2008 are to support generation of final analyses and reports.
7. Miscellaneous
Nothing at this time.
Texas Department of Transportation maintains the information collected through this form. With few exceptions, you are entitled on request to be informed about the
information that we collect about you. Under §§552.021 and 552.023 of the Texas Government Code, you also are entitled to receive and review the information.
Under §559.004 of the Government Code, you are also entitled to have us correct information about you that is incorrect. For inquiries call 512/465-7403.
6 of 6