Additional problems

I have other problems with the understanding of the real meaning of some
parameters:
a) Highest top-width number of landslide mass,
b) middle top-width number of landslide mass,
c) lowest top-width number of landslide mass,
In particular it is not clear if they describe the geometry the landslide
mass could assume in the channel once it has failed or something else.
The "number" means a length in meters. And last, what about the "arrival time
elevation increase criterion" that is not specified in the user's manual ?

Best wishes.

Marco Masetti

We have included a landslide example with our DAMBRK program. Example problem P08.DBK illustrates how to use the landslide option in DAMBRK.

The Top-Width Number data entry refers to the entry number in the Cross-Section Geometry input screen that represents the center of mass for the reservoir landslide mass. Therefore, this is between 1 and the number of entries that you have defined in the Cross-Section Geometry input screen.

The Thickness data entry refers to the thickness (into the bank) of the material that will then fail (prior to failing). The model uses this to determine the increase in cross-section top-width at the time of failure.

Note that the on-line help has more detailed information that is not included with the current User Manual.

The Landslide Description screen will be presented if you have specified in the Channel Cross-Section Description screen that a landslide occurs along the downstream routing reach for the current cross-section.

NOTE: You can over-ride any entered landslide data using the landslide entry in the Project Description screen--thereby allowing you to analyze the routing reach without a landslide. The maximum number of adjacent cross-sections (and corresponding downstream routing reaches) where a landslide can occur at is 6. Also, this screen does not apply for the downstream extremity cross-section.

To view a graphical plot of the current cross-section, press F3 . This cross-section plot is extremely helpful while defining the cross- section and useful in checking your input data for errors.

Below is a list of the Landslide Description data entries, and a short description about each entry.

DURATION OF LANDSLIDE (hr)
Time of duration for the landslide. This is usually in the range of 15 seconds to a few minutes, although the value must be entered in hours. [55-TSL]

HIGHEST TOP-WIDTH NUMBER OF LANDSLIDE MASS
Channel cross-section top-width number of the highest portion of the reservoir landslide mass. [55-LSU]

MIDDLE TOP-WIDTH NUMBER OF LANDSLIDE MASS
Channel cross-section top-width number of the middle portion of the reservoir landslide mass. [55-LSM]

LOWEST TOP-WIDTH NUMBER OF LANDSLIDE MASS
Channel cross-section top-width number of the lowest portion of the reservoir landslide mass. [55-LSL]

MAXIMUM LANDSLIDE MASS BANK THICKNESS
Greatest thickness (depth into the bank) of the landslide mass, at the landslide's middle top-width. [56-THKSL]

ANGLE OF REPOSE FOR DEPOSITED MASS (degrees)
Angle of repose that the deposited material from the landslide mass assumes in the bottom of the reservoir at its center or mid-point. [55-ALPHA]

POROSITY OF LANDSLIDE MATERIAL
Porosity of the landslide material, entered as a decimal fraction. [55-POR]

Also, the on-line help has more up-to-date information on the Arrival Time Elevation Increase Criterion. Pressing F1 lists the following information.

ARRIVAL TIME ELEVATION INCREASE CRITERION
Specify the increase in water surface elevation over the initial conditions water surface elevation that is used to determine the arrival time of the routed flood wave. Leaving this entry blank causes the program to default to 1.0 ft.

By looking over the example problem I referred you to, you should be able to better understand what is going on.

Please contact me should you have any additional questions.

Sincerely,

Chris E. Maeder, M.S.
Senior Technical Engineer
chrism@bossintl.com