There are three entries to this area, two of which are connected by trails.
One entry is at the north end of NE 22nd Ave, and accesses a short (1/4 mile) trail that leads to Whipple Creek. When you hit the slope down to the creek, the trail splits. While it is possible to follow either trail, and then parallel Whipple Creek to meet up with the other trail and return to the fork, the walk along Whipple Creek can be difficult to follow, especially when the grass is very tall or the water overflowing the banks and there are blackberry bushes to contend with. When I visited in the summer I was not able to make my way through, but in January I could, since the grass was flattened down making it easier to find my way.
The other two entries are at the ends of 164th St and 165th St. A loop trail connects the two entries, and then connects with a trail that runs to Whipple Creek making for about 1/2 a mile of trails. There are some great photos posted by Michelle Rau on Google Maps.
One note of caution: The map at the 22nd Ave entry to Whipple Creek Hollow Natural Area actually shows a trail along Whipple Creek from NE Union Road, however, if you go there to find that trail, you will instead find a gate across the access with a sign that says Keep Out.