dambrk modeling questions

Gentlemen:

I knew at the time our company purchase this software that it was a overkill, however once we got familiar with it we could us it on other project. Unfortunately we need to get a simple problem completed.

We have a small lake which has a water surface area of 4.0 ac. The downstream channel to analysis is only 1000 feet in length an we will have 4 cross sections. The questions are as follows:

1. How do I enter cross sections? I am used to entering cross section as distance Lt.or Rt.of the centerline along with the elevation at that point. (ex.. 46',980.0).

2. Do you enter the flow hydrograph for the drainage area into the lake? The example shows a few numbers for a hydrograph, like beginning of storm, peak flow and end of storm, is this all that is needed?

3. The biggest problem is just how do enter and arrange the data for such a simple problem?

Dear Hugo :

Please see my responses to your questions, below.

If you have any additional questions or need any further information, please contact me again.

Sincerely,

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

> 1. How do I enter cross sections? I am used to entering cross section as distance Lt.or Rt.of the centerline along with the elevation at that point. (ex.. 46',980.0).

To enter cross-sections, from the main menu select the following menu items:

Input Data
Enter Input Data
Reach Description

You will then enter the Cross-Section Location Selection dialog box. From this dialog box you enter the cross-section location ID, which corresponds to the river mileage of the cross-section, measuring in a downstream direction. Use "Add" to add the cross-section location.

Next, use "Select" to select the cross-section you just added and you will be placed into a menu describing the cross-section data. From this menu select Cross-Section Description. From here, press Page Down and Page Up to go between data entry screens. Note that the Cross-Section Geometry data entry screen is used to enter the cross-section geometry, which is defined as elevation versus top-width pairs. DAMBRK requires the same number of top-width pairs at each cross-section.

> 2. Do you enter the flow hydrograph for the drainage area into the lake? The example shows a few numbers for a hydrograph, like beginning of storm, peak flow and end of storm, is this all that is needed?

You define an inflow hydrograph at the upstream reservoir. This inflow hydrograph defines the length of the simulation run. Therefore, if you define a 10 hour hydrograph, the DAMBRK model will only run for 10 hours. So, it is important to define a hydrograph that is long wnough in elapsed time so that it is routed all the way downstream.

> 3. The biggest problem is just how do enter and arrange the data for such a simple problem?

The best way is to review Chapters 3 and 4 in the DAMBRK User Manual. Chapter 3 provides you with an overview of how to define the DAMBRK model, and Chapter 4 gets into the specifics of each data item.