Tonight I was thinking of a way to increase productivity when creating drainage area maps. Drainage area maps are pretty simple to produce. The plan is basically contours, drainage areas, flow arrows and a drainage table. Using parcels can be a great way to create drainage areas. So I decided to create a simple parcel style that would automatically display the drainage area ID, acreage and runoff Q. This label style would save me time from creating small blocks or text to identify drainage areas.
The first step is to create two simple expressions under my Parcel/label styles/area. My first expression was for my pre-development areas (existing drainage area map). I used a runoff coefficient of 0.30 and the Town of Flowermound 100 year rainfall intensity of 8.82. Then I created a post-development expression (proposed drainage areas) with a runoff coefficient of 0.90 and rainfall intensity of 8.82.
Next I created two new label style under Parcel Label Styles/Area Style called DA-PRE and DA-POST. In my new label styles I added the new expression that we just created into the proper label styles. Then I turned on the boundary option in the styles and used a circle. And that’s basically it. See my images below for examples. Hopefully this will give your more ideas with using expressions. Later