STORAGE AREA

[Richard Schneider]

I am modeling a dam. Made storage area upstream of dam. Allowed for one xsection between storage area section & dam section. Unsteady flow data has 3 boundary sections-1. downstrm (normal depth) ,2. T. S. Gate Openings and 3. storage area (lateral hydrograph). Hydrograph has peak flow of 620 cfs. Hydrograph is direct read from dss file. Initial conditions has 50 cfs initial flow at storage xsec.

PROBLEM When I run unsteady flow, the results show only the 50 cfs initial flow and is not picking up storage lateral hydrograph.

Ideas??

[MichaelG]

The problem that you report sounds like it is related to the time window. Be sure that your simulation time window (set in the unsteady flow manager) is encompassed by the data in the DSS file. Another consideration might be a connectivity error. The reach connections can be found on the Geometric Data Editor under Tools – reach connectivity. For example; two cross sections are required upstream of the dam – one to connect to the storage area and one for the unsteady flow equations to work. Two boundary conditions, internal or external must always be separated by at least one computational cross section.
A tutorial for developing the input data for modeling a dam breach with RAS using a storage area to depict the reservoir was published by the State of Colorado a few years ago. Their document can be found at http://water.state.co.us/DWRIPub/Documents/GuidelinesForDamBreachAnalysis.pdf
That document describes how you enter the data for using a storage area to describe the reservoir. An example of the data structure for describing the reservoir with cross sections is included in the example data sets with RAS 4.1 (Bald Eagle Cr.).
Michael

[Author]

Posts