The nymphs that are most vulnerable to catastrophic drift are those that are close to emerging and are therefore more active on the streambed. To imitate these insects, choose patterns with well developed wing pads. Since the actual emergence is often temporarily suspended, emergers and dry flies that imitate hatching insects are less productive fly choices for the catastrophic drift.
Color choice is vital. Dark colors such as brown and black show up well in turbid water, but lighter colors tend to disappear. It’s also important that the contrasting colors in your flies really “pop.” Fluorescent colors retain their visibility in muddy water and work great when combined with a dense primary color.
MW Coulee Scud (Mat Wagner)
HOOK: 2X-strong wet fly hook (here a Daichii 1530), sizes 12 to 16.
THREAD: Tan 6/0.
BODY: Tan UV Ice Dub.
SHELL: Clear Scud Back, 1 /8 inch.
BEAD: Fluorescent bead.
RIB: Black wire or thin black mono.
LEGS: Tease the dubbing to imitate legs.
MAT’S TIP: Twitch the fly if the dead drift doesn’t work; make it pop and jump.
The MW Scud is an example of an ideal nymph for high, turbid water. Not only does it represent a common food source for high flows, but the main brown color also shows up well and the bright fluorescent pink hot spot adds the needed contrast to excite trout.
Getting your flies to the fish is a challenge that involves first finding where they are and then adding enough weight to break through the strong vertical current layers. Trout tend to push to the banks and bottom during high flows, so you need to identify prime feeding locations. Erosion is greatest along the outer banks, which creates undercuts, widens river bends to accentuate meanders, and also dislodges potential meals for trout from the soil. River bends and the initial straight section just downstream of them are ideal locations for nymphing after the storm, especially with a San Juan worm or crane fly imitation.
Add enough weight to compensate for the strong current and deeper water. Your fly needs to be contacting the bottom; trout will not fight the strong current to chase very far. If you don’t feel the bottom occasionally or hit a snag once in a while, add more weight. Consider using a heavily weighted anchor fly, perhaps something tungsten, in tandem with one or two other flies. An anchor fly’s main purpose is to carry the other flies to the bottom. Keeping your casts short will allow you to better maintain contact with the bottom.
Dry Flies: Normal insect activity is often suspended during a high water event, so a dry fly such as Parachute Adams might not produce well. But if high flows occur following heavy summer rains, terrestrial insects such as beetles and ants may wash into the river. Recolonization for ants is a common summertime occurrence, when long columns of ants head out to form a new colony. Summer rains that coincide with ant migration close to the stream can wash countless ants into the water to end up in eddies and depositional areas that collect foam and flotsam. Cast an ant or beetle to float among the debris, and you might just be surprised that a trout has noticed an easy meal opportunity among the clutter.
Since beetles often cling to streamside vegetation, heavy spring or summer rains cause these insects to drop into the water. Dead drifting a beetle imitation along the shore where branches overhang the water can be productive, especially if you are fishing in or just after the rain. Greedy trout are often positioned just downstream, eagerly awaiting a terrestrial insect.
Streamer Fishing: When the feeding lies and home sites of trout are altered by high flows, trout reshuffle to new locations according to the hierarchy of fish size that determines their pecking order. Smaller and medium-size fish tend to be more mobile until they evaluate new feeding lies and reestablish new locations. Before the hierarchal stability allocates a new site to each fish, there is a lot of jockeying for position, and opportunistic larger trout intercept smaller fish as they redistribute to new locations.
Larger trout cruise the soft-water edges along the banks of the stream in the hope of picking off smaller fish displaced from their normal lies and feeding routines. This makes high water a good time to throw a streamer. The smaller fish that large trout prey upon generally hold along the river margins, while their feeding sites are often in swifter current. Large trout typically target these smaller fish when they are on the move, and hence most vulnerable. Look for soft-water edges along runs and the back edges of gravel bars, where smaller trout often stage on their way to feeding lies. Minnows often hang out there, too, and large trout cruise these areas to find vulnerable prey fish. Try dead-drifting, swinging, and stripping a streamer through these zones.
As with nymphs, your streamer choice should be based on visibility in turbid water, and dark, dense main colors with exaggerated contrast work the best. The black and fluorescent green combination of Ben Furimsky’s Gunni Special is effective in fast muddy water, especially if the water has the slightly greenish discoloration often found in summer. The fluorescent chartreuse remains highly visible under those conditions. Even though the fly is weighted, using a sinking-tip line will help get the Gunni Special to some of the deepest lies, and a short leader increases the percentage of landed fish.
The abrupt, drastic changes caused by fast-rising water is a game-changer for fish and other stream residents. But high water doesn’t mean that your whole trip is a wash. While you may have to make some adjustments in your fishing strategies and take a bit more care in wading, you can still catch fish and salvage a trip to the river that might otherwise have been unproductive.
Jason Randall’s second book, Feeding Time; A Fly Fisher’s Guide to What, Where and When Trout Eat, is a must-read for all anglers. He is a veterinarian certified in fish health and medicine.