How to use the National Hydrography Dataset (NHD) in ArcGIS Online by Al Rea

Have you ever wanted to get a very quick view of what’s in the NHD for an area that you haven’t downloaded?  Even if you have the data on your hard drive, I’ve found the quickest way to see the basic NHD features is through the ArcGIS Online (AGOL) viewer. I’ve made a very simple web map in AGOL that accesses an NHD dynamic map service from The National Map (TNM). To give it a try, open this link: http://bit.ly/1puvHOn

Zoom to your area of interest. You can use the standard map zoom tools, or type in a place name or street address in the search box in the upper right of the window. You need to be zoomed in to a scale where the NHD streams can be displayed reasonably. If you don’t see any streams on the map, click on the “plus” symbol in the upper left corner of the map to zoom in more. Notice that in the legend there is a scrollbar once you’re zoomed in so that streams begin to display. The NHD streams are called “Flowline – Small-Scale” or “Flowline – Large Scale”, and appear at the bottom of the legend. You will need to zoom in so that the scale bar in the lower left corner of the map shows one mile or less to see the ephemeral streams, which are in a dashed brown line style. (Note that ephemeral streams are not shown in all areas.) Intermittent streams are shown in a light blue dashed line style. If you have used this service in the past, you may notice that the symbology has changed recently.

There are several other map services from The National Map that might be of interest to you. A listing can be found here: http://viewer.nationalmap.gov/example/services/serviceList.html. You can bookmark that URL, or just remember this: Search for The National Map, go to the main page, and on the left under Products and Services, click on the Framework Web Feature Services link. You should be able to open the ArcGIS Online map above without having an AGOL login account. If you do have an account, you can save the map as your own and customize it as you like. The TNM services listed above may also be added to your map, along with anything else that is out there on the web.