It appears your solution would be to do the following:
You can set the points and distance along your line to then create the buffer to select those waterways in your area.
You could use the Create Points from Lines
Construct Points creates new point features at intervals along a selected line. For instance, you could use Construct Points to place utility poles along an electric line. You can create a specific number of points that are evenly spaced, or you can create points at an interval you choose based on distances or m-values.
There are three options you could use:
Number of points—A specific number of points are created along the selected line so they are evenly spaced. In this example, two points, evenly spaced, are created on the line.
Two points created on the line
Distance—The points are created on the selected line based on an interval that is measured in map units from either the start or end of the line. Arrows are shown to indicate the direction of the selected line. In this case, the line starts at the left and ends at the right.
Arrows are shown to indicate the direction of the line
By measures (m-values)–The points are created on the selected line based on an interval that is measured in m-values from either the start or end of the line. To use this option, the line must have m-values, and they must be in order (consistently increasing or consistently decreasing) to be valid.
Alternatively, this may be another approach
Take your point features and create a buffer to the 6 km area of interest you have set.
Then use the select by location:
Then you could create a feature from selection
Also, if you wanted to export to data your selected feature files you can by:
- Right-click the layer in the table of contents and click Data > Export Data.
- Click the Export arrow and click All features, Selected features, or All
features in View Extent.
- Click the option for the output coordinate system you want to use.
- Click the browse button Browse and navigate to a location to save the exported data.
- Type the name for the output data source.
- Click the Save as type arrow and choose the output type.
- Click Save.
- Click OK.