Modifying CCF or IDF Coefficient in MiTS 2 and MiTS 3

In MiTS, you can edit the CCF or IDF coefficient to be used in your drainage design. However, there is a bit of a difference between MiTS 2 and MiTS 3’s coefficient adjustment for the Drainage module due to the different interfaces.

MiTS 2 #

Adjusting IDF Coefficient in MiTS 2

1. Click on the Drain button

2. Go to the Properties tab in the RHS panel

3. Click the ‘…‘ button at the end of the Location row to open the Location window

4. Select the location for your project and the Design ARI.

5. Adjust the CCF value or the IDF coefficient in the Fitting Constant row

MiTS 3 #

In MiTS 3, the coefficients of a published rain gauge are read-only. They are the values printed in the design manual for that gauge, and the report labels them as such. To use your own coefficients, change the IDF Source to User λ, κ, θ, η coefficients (or, under MSMA 1st Edition, User a, b, c, d coefficients (MSMA1 equation)) and enter the values there. Turning CCF on or off is still a single setting, CCF Inclusion, beside the IDF source.

Projects saved before this change still calculate with the same values. If you had edited a rain gauge’s coefficients, the project opens with those edited values as User λ, κ, θ, η coefficients, one row for each ARI, with the CCF values unchanged. The old gauge name is kept for the record. Add a Location note so the report says where the values apply. See Choosing the IDF Source for the full description of each source.

You can make these changes in both the RHS panel and Project Settings.

RHS Panel #

Adjusting IDF Coefficient in MiTS 3 from RHS Panel

1. Click on the Drain button

2. Go to the Properties tab in the RHS panel

3. In the Rainfall Intensity section, set IDF Source to User λ, κ, θ, η coefficients

4. Set CCF Inclusion if you need to turn CCF on or off

5. Click the ‘…‘ button at the end of the Details row. This opens the Rainfall Intensity page of Project Settings, where you enter the coefficients (next section)

Project Settings #

Adjusting IDF Coefficient in MiTS 3 from Project Settings

1. Go to Options > Project Settings

2. In the Parameters dialogue box, go to Storm Design > Design Rainfall > Malaysia > Rainfall Intensity

3. Set IDF source to User λ, κ, θ, η coefficients

4. Choose the Coefficient format. One coefficient set for every ARI uses one λ, κ, θ, η set and lets the return period vary through $T^\kappa$. Separate coefficient set for each ARI takes a full row for each ARI. Click Add ARI row for each ARI the analysis uses

5. Enter λ, κ, θ, η and CCF. If you are adjusting a gauge’s published values, look them up first with IDF source set to MSMA2 rain gauge, which shows the selected gauge’s coefficients read-only, then switch to User coefficients and type them in

6. Enter a Location note, for example Industrial site near Jalan Ampang, Kuala Lumpur. It is printed in the reports to show where the coefficients apply

With the separate-set format, every ARI the analysis requests needs exactly one complete row. If a row is missing, the run stops with a message naming the ARI. MiTS does not borrow the nearest ARI’s values.