April 28 2008 |
How do I go about producing tapered streams?
Mapping Center Answer:
You'll need an attribute that indicates the symbol size you want to use. If your attribute is specifically for symbol size, then you could use Unique Values symbology or if the attribute is something like Mean Annual Flow, you can classify the features based on that using the Graduated symbol method under the Quantities heading on the Layer Properties dialog's symbology tab.
If you're mapping in the U.S., the NHDPlus data has a mean annual flow attribute (use the MAFlowUA attribute, which means the flow was calculated based on upstream drainage area). NHDPlus data is a value added dataset based on the USGS's NHD medium resolution hydro data. If you're making small scale maps this data will work well. In fact, we've been working on making such a dataset recently; so I zipped up an example for you to download [10.2 Mb]. There is a flow class attribute, which ranks rivers in classes of flow from 1 being the most (.e.g., lower Mississippi River) to the largest number for the least significant river in the dataset.
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