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Getting Started - A Tutorial for L-THIA
This document describes how to get started in using the L-THIA WWW system. An example application of L-THIA WWW is presented to describe how to use the system.
Problem Statement
The local zoning commission has been asked by a developer to rezone a 25 acre area near West Lafayette, Indiana (Tippecanoe County). The developer asks that the area be rezoned into 20 acres of low density residential and 5 acres for a commercial district. The land currently is zoned agricultural. The developer plans to build in two stages. At the end of the first development phase, the area will consist of 20 acres of low density residential housing and 5 acres of agricultural land use. At the end of the second development phase, the area will consist of 20 acres of low density residential housing and 5 acres of commercial land use. The area has hydrologic group B soils (this information can be obtained from maps within the L-THIA WWW system). Use L-THIA to evaluate the effects of the proposed land use changes on average annual runoff to help the zoning commission in its rezoning decision.
L-THIA Input
To begin using L-THIA WWW, select the arrow to the left of the input option from the menu on the left. You can select either basic or detailed input. With the basic input the user can chose from 8 different land use types. This input form is for involved community people who many not have a background in land use planning but are concerned with development in their area. The detailed input has 13 different land use choices plus a custom field. If the custom field is chosen the user can create a new land use by defining the appropriate curve number. Land use planners, developers, landscape architects and consultants are the intended users of this type of input. For this scenario, the basic input will be used.
Scenario Name
The scenario name will be used in tracking your L-THIA analysis. In the example shown in Figure 1, "sample" is used as the scenario name.
Location
Select the location of the area being analyzed (State and County) from pull down menus. For the example problem described above, the location is Tippecanoe County Indiana. The location information is used to select the appropriate rainfall data for running L-THIA.
Units
Select the units that will be used in describing the area you are analyzing. Selection of English units for area units will result in the use of English units in the output. Selection of metric units will result in the use of metric units in the output. In the example described above, areas were given in acres so acres have been selected as the area units.
Hydrologic Soil Groups
Hydrologic soil group is a soil property that characterizes the runoff tendency of the soi. If you do not know the hydrologic soil group for an area you wish to analyze, this information can be obtained after selecting the state of interest in state field. If you click to view the map, a WWW browser with the hydrologic soil group of the state will be displayed. You can zoom to the location of interest to determine the appropriate hydrologic soil group to use in the analysis.
Land Use
In Figure 1, the area of each land use/soil group is entered for each of the time periods considered. The land uses considered are selected from the SELECT LANDUSE menus. In the example problem described above, the hydrologic soil group for the entire area was group B. In the first scenario year all of the land (25 acres) was being used for agriculture. During the second scenario year only 5 acres was being used for agricultural, while 20 acres was in a low density residential development. And in the third scenario year 20 acres was in a low density residential development and the remaining 5 acres was a commercial development. At the bottom of each column there is a summation of the amount of land described for that year. Be sure that all of the columns add to the same amount of land. You may need to click on another entry box for the last value entered to the included in the totals. Once all the information is entered, select the Run L-THIA button at the bottom of the WWW page.
If the detailed input was selected, the user can define a custom land use. In the land use drop down menu, choose the custom option. In the pop-up box, enter a name for the land use and the appropriate curve number separated by a comma. The last column of the input sheet is labeled "SELECT Land Use Similar to the Custom Land Use for NPS Estimation". In this column select the land use that most closely represents the custom land use for the approximation of NPS pollution.
L-THIA Output
Once L-THIA runs (a few seconds), the results will appear in the WWW browser as shown in figure 2. The average annual depth of runoff for each land use and soil combination is also reported as shown.
Runoff
Average annual runoff volumes are also reported in tabular form in this section (Figure 2). Volumes are reported for each time period analyzed.
If you are going to want to review your data later, provide a user name and password at the bottom of the page.
The runoff depth and volume results can also be viewed in graphical form by selecting the bar chart or pie chart option from the menu on the left side of the web browser window. The results are shown in Figures 3 and 4.
Non-Point Source Pollution
Nonpoint source (NPS) pollution results can be obtained by selecting NPS in the menu on the left (use the mouse to click on the triangle symbol beside NPS). A list of NPS outputs will be made available as shown in the figure at the right. Select the NPS pollutant of interest and then select the format that you wish to use when viewing the data. Figures 6 and 7 show the NPS nitrogen that is expected to be generated for each land use area analyzed. Other NPS pollutant results can be obtained by selecting the NPS pollutant name and then the format of the output from the menu.
Completing New and Viewing Previous Runs
Additional model runs can be made by selecting the Input option from the menu on the left to return to the input form. If you saved your data from a previous run, the input data can be reloaded into this form.
Results of previous L-THIA runs can be viewed by selecting the Output option from the menu on the left. Enter your user name and password. The list will include all previous runs saved under that user name.
