ENG515 - ASSIGNMENT 2 - USE OF HEC-RAS FOR ANALYSIS OF UNSTEADY FLOW - 1 OF 2
CHARLES DARWIN UNIVERSITY
ENG515 WATER RESOURCES ENGINEERING
ASSIGNMENT 2 - USE OF HEC-RAS FOR ANALYSIS OF UNSTEADY FLOW
In these computer sessions, and with this assignment, you will have opportunities to use HEC-RAS to perform
an unsteady flow analysis of a network of reaches containing junctions,
idges, culverts, and hydraulic
connections. The geometric data for this study illustrate multiple unsteady flow applications in HEC-RAS.
This work focuses on modelling and evaluating hydraulic connections, and hydraulic parameters in an unsteady
flow environment. You should start by becoming familiar with modelling
idges, culverts, multiple reaches,
and junctions.
You will need to ca
y out the following analyses and write a
ief report on your findings (see below).
The data files are available in the 1-d unsteady flow examples of the HEC-RAS software (Multiple reaches with
hydraulic structures/3ReachUnsteady.prj). You need to load this information into HEC-RAS at the start of your
work and convert the project from US customary to SI units.
Geometric data
The geometric data consist of two channels (Fall River and Butte Creek) connected by a junction. Three
structures are included: a culvert roadway, and two
idges.
The culvert roadway is located at River Station 10.1 on the Fall River Upper Reach and
idges are located at
River Station 0.22 on the Butte Creek Reach and River Station 9.55 on the Fall River Lower Reach.
The following hydrographs (Fig. 1) have been selected as representative of the design conditions. These are
already input in the example. Several issues have arisen with regard to development of the land around this
drainage system and with modifications to the existing
idge at RS 9.55 on the Fall River Lower Reach.
Figure 1 Hydrographs representing design conditions
ENG515 - ASSIGNMENT 2 - USE OF HEC-RAS FOR ANALYSIS OF UNSTEADY FLOW - 2 OF 2
Tasks
a. Become familiar with the system described by analysing the flow behaviour for the status quo.
. Examine the culvert roadway located at River Station 10.1 on the Fall River Upper Reach. It is feared
that a blockage to its circular, and box, culverts may cause flooding problems. Find the implications of
2.4 m of blockage (almost 100%) to these culverts throughout the flood event described by the
hydrographs above.
c. The
idge at River Station 9.55 on the Fall River Lower Reach is to be modified and upgraded for
improved strength as the structure was found to have cracks in its piers and erosion was present on the
ive
ank below the road deck. Create a new design that includes wider piers and abutments but does
not increase the peak water surface at the
idge by more than 0.25 m during flood conditions.
d. Tree planting will occur upstream: it is estimated that this may decrease the flow in both hydrographs
(Fig. 1) by 1% per annum over a 30-year period, stabilising thereafter. Experiment by changing the
hydrograph and/or other data to ascertain the likely implications of this reforestation over the 30-year
period from planting to maturity.
Submission of a
ief report for this Assignment must be made via LearnLine in .pdf file format before the dead-
line (1630 ACST, Wednesday Week 11).
The length of the report is limited to 600 words ± 10% (excluding Appendices) and not more than six pages of
A4. It should cover the outcomes of the investigations in Parts b), c), and d), above. It should be written to a
professional standard, using past tense and, in general, passive voice. Students should retain an electronic
copy of the HEC-RAS files they produced during this Assignment as a spot-check may be made to confirm
the submitted results. The report may include a number of screen-shots by way of illustration. Marks will be
deducted for mistakes in spelling and grammar. A word count must be included at the end of the report. The
work you submit must be your own work - plagiarism will result in a zero mark for this Assignment.