Monday, July 1, 2019

DDMSW HEC-1 Quick Start

DDMSW is a program of Maricopa County to calculate and manage drainage projects. This blog post tells the simplest way to get started using the HEC-1 hydrology part of DDMSW.


1. DDMSW keeps its projects in its own central database on your PC. For good file management, always use the File, Project Management menu to Backup your project to your project team's folder location after working and Import it from from there when you return to the project.
2. DDMSW sometimes crashes hard and badly (from Help, for example), but your data is usually safe. To end DDMSW from Task Manager, look for stl.exe.


Usage case 1 is using DDMSW alone to create the simplest HEC-1 model possible for a single subbasin in Maricopa County with no GIS input.  Scenario 1 is only best for the simplest of watershed models or to begin getting familiar with how HEC-1 works in DDMSW. If there much mixing of soils, land use types, and sub-basins at all, GIS input is worthwhile (especially with my DDMSW Export tool for AutoCAD), even if you are an AutoCAD user.
Watch the video


Figure 1: Form to create a project: Select Project - Add
Chose File, Select Project. then click the Add button and select Hydrology and Hydraulics. A form will appear where you choose the defaults for the project. Fill out what you can including the values shown in Figure 1. Then  stay on this form.


Figure 2: DDMSW rainfall grid map 52, Central Phoenix
When you Select Project, a form appears in which you have to set many project defaults including the Rainfall. You can select NOAA2, NOAA14, or CUSTOM. It's important to notice that NOAA2 (which is obsolete) may be initially selected. With NOAA2 or NOAA14, to select rainfall using only DDMSW (no GIS maps), you have to look at the DDMSW rainfall grid maps (see Figure 2). The maps are in left-to-right rows starting at the southwest corner of Maricopa County. If you select CUSTOM, you can enter precipitation values for your location (the NOAA Precipitation Frequency Data Server is a good source) under the Hydrology, Rainfall menu.

Note that in DDMSW, Rainfall is associated with a Major Basin "MB".

Use the Save then OK buttons to continue.

Use the Hydrology, Rainfall menu to open a form where you enter either the precipitation for your location (CUSTOM rainfall; you may be able to get away with entering only the 6-hour precipitation) or the map cells to average for your Major Basin. To look up cells, first click the Map button to see the cell grid map. To add ranges of cells, use the Add and Save buttons. When you are done adding cells to average, use the Update button to automatically enter average precipitation data for your Major Basin. Then use the OK button to continue.


Next, use the Hydrology, Sub Basins menu and its Add button to add a subbasin. Add all the values you can without using any of the Custom boxes. Then click OK to continue.


With a Sub Basin created, either use the Hydrology, Land Use Defaults menu to Add your own custom Land Use type definition(s) first or go directly to the Hydrology Land Use menu to Add Land Use types one at a time and assign it/them to your Sub Basin. After adding each Land Use assignment, use Save. The area of all your assignments must add up to the Sub Basin area. Use OK when you are done assigning Land Use types to your Sub Basin.


Follow the same procedure you did with Land Use to assign Soils to your Sub Basin.


Now that there are Soil and Land Use assignments for your Sub Basin, return to the Hydrology, Sub Basins menu and use the Update button to do some of the most important magic we use DDMSW for, namely iterating TC with rainfall excess intensity based on soil loss parameters.

If you are using HEC-HMS or a HEC-1 model outside DDMSW, this is as far as you have to go with DDMSW. The Green and Ampt and Clark values are now listed for your Sub Basin in this form.


1. Use the Hydrology, HEC-1, Network menu and
a) the MB button to assign Major Basin 1
b) the Add button to add a Basin, your Sub Basin, then Save
c) the Create Draft button to create a dummy model (You will need to select a folder for the model runs path. Any folder will do. Then you will have to use Hydrology, HEC-1, Network and the Create Draft button again.)

2. Use the Hydrology, HEC-1, Model and
a) uncheck Update HEC-1 and then Save and Run Model for the dummy
b) check Update HEC-1 and then  Run Model with your data


Use the Results button to see flows.
Use the Output button or Hydrology, HEC-1, View Output to see the HEC-1 output file.


Usage case 2 is using DDMSW with imported shapefile maps to to create the simplest HEC-1 model possible for a single subbasin in Maricopa County based on GIS maps. See my posts on AutoCAD, GIS, and DDMSW if you are an AutoCAD user and need help preparing shapefile maps for this purpose. There is less work to do in DDMSW even for the simplest model if you have GIS maps prepared. And for more complex combinations of soils, land use types, and sub-basins, GIS input is the only sane way to use DDMSW. For now, I am leaving this detailed description for another time. So I will refer you to Usage case 1 for DDMSW HEC-1 help and to this video for help bringing GIS maps into DDMSW.

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