How To Fly Fish Flooded Rivers

Welcome to that time of the year where we obsess over weather patterns and river levels. Almost daily we'll try to predict when the two will meet together in that sweet spot of river post-flood dropping and clearing, and with it a new mob of fresh run fish.

There’s no escaping reality though, you gotta pay to play. Perfect conditions on a river like the Tongariro won't come without first dealing with some decent flood events - which, as Murphy's Law would have it, doesn’t usually time well with your fishing plans.

So, what can you do to try and salvage a fishing trip when you’re dealt a rough hand by the weather gods? You can still go fishing, and you can still catch fish, you’ll just need to change tactics and work a little bit harder.

In this article, Chris Dore shares few tips on dealing with flooded rivers, and how to approach things when it starts to drop.

A fly fishing river in flood in New Zealand



Chances are while they were low, dry and weedy on your last visit, they may hold sufficient water now, and just maybe a few fish. Fish will seek out cover in side channels and will stack up making it an easy proposition to cover them well. They'll be pretty happy where they are so you can have some amazing sessions on a piece of water that’s normally only ankle deep.


Fish the edges, inside bends and other softer water areas. This is where the fish will be found, and are accessible in high, dirty flows. Make sure to work your way through all of the soft water from the inside of the fast bend, right though to your feet.

Changing the weight of your fly a couple of times is important if you want to effectively cover the deep, faster stuff and then move into the shallow water without constant drag and snags.

The key here is to cover every inch of water, so persevere long enough and you’ll put a fly right in front of a fish's face, which you have to do because they’re not coming looking for it.


Dark sz10 and sz12 nymphs, big, black streamers, or large, bright glo bugs are the order of the day here. The fly needs to be seen, and it needs to stand out amongst the plethora of debris coming downstream.

Trout only have a short period of time to make the decision to eat, so make it obvious and unmistakable.


It’s perfectly possible to catch fish in water that many deem unfishable. You just have to fish flies that the fish can locate in a way that enables them to locate them. Pulling large, rubber-legged nymphs, hot head patterns or streamers can turn a potential shocker into a decent day out.


We have some of the most productive lakes in the world, so why not explore them. These are likely to remain clear throughout, and the sight fishing they provide is often second to none.

Even though the stream might be spewing out chocolate milk into the lake there will always be an obvious seam where dirty meets freshwater, and the trout will hang out here picking up easy meals.

Rip a streamer through or dead drift some nymphs under an indicator. This kind of fishing can be phenomenally good.


Don’t try and cross a flooded stream, watch out for unstable banks, let someone know where you’re going and when you’ll be back, and wear good gear. Never underestimate a river at full flow, carry a wading staff and always have an exit strategy.

Fishing dark flies on the flooded river edge produced this trout


After a big flush the shape and structure of a river can change and they may not fish the same as they did pre-flood. This is normal following a big fresh but many anglers struggle to come to grips with the changes in the rivers and behaviour of post-flood fish.

Good anglers can always go to a new river, read it and find fish. Those who simply learn which pockets usually hold fish and just target those spots are often lost as their favourite holes change. These simple rules will help you re-learn your local after a decent flood event, and even if it’s not a massive blow-out put them into practice and locate a bit of new water anyway.


Look for permanent structure like large boulders, cut banks and depth – those things that are unlikely to change. Chances are the trout aren’t holding in that straightened gravelly reach. Wider sections of riverbed with lower banks are often better equipped to handle big flows than narrower, channeled sections as floodwaters can spread and gouge out the riverbed much less.

Search out wider pools and this is often where post-flood trout can be found and focus on backwaters, wider areas of river channel where the water won’t have torn through, and inside bends where the force of the current will have missed. Look for stability and darker, algae-covered rocks as this is where the food will be.


If they’re not feeding, trout seek cover. Larger, deeper pools seem to be where numbers can be found. As rivers settle back in, fish will venture out and repopulate greater areas but for now, focus some time on the deep pools and drop-offs. Trout will often feed closer to cover without an abundance of food to pull them into the open.


With a big washout, a trout’s diet becomes heavily focused on food items that survive. Cased and free-living caddis often survive secreted within holes and crevasses in boulders and sizable rocks, while terrestrials such as willow grub, beetle and cicada can often become the mainstay. Whilst mature mayfly nymphs often wash out in floods, juveniles in egg form often remain, and so trout may feed on these much smaller nymphs along inside bends and other places less affected by swollen flows.

Following a big fresh many mature mayflies get washed out. The remaining nymphs are often tiny juveniles that survived, secreted in the tightest of cracks and crevasses. However, caddis are much more resilient post-flood and so I look toward larger free living and horn-cased caddis as my after-flood staples.

Streamers too offer a well-needed mouthful, so keep a Dore's Mr Glister handy, and don’t be shy to send a squirmy wormy for a swim to prospect likely looking water.

And with the redds being disturbed and water colour being spot on the glo bug really comes into its own so how a selection of sizes and colours on hand, and chop and change until you find the one that will do the damage.


With flooding comes debris and fish will often sample a number of things, twigs, leaves and gravel included. With the abundance of debris in the drift now, trout will develop a very quick ejection reflex on anything they find isn’t legit.

Notice an abundance of super-fast ejections on your nymph this past week? Are the fish eating and dropping your fly super-fast? That indicator dipping erratically?You need to set faster. Control your drift, recover slack line and consider a fast, low side set.


With less food on offer fish will only feed when it is worth their while post summer fresh. This may be a few brief periods when the invertebrate drift is heavy, or mid-morning when the willow grub really get going. This probably won’t last for long so you need to make the most of any activity you find. If the fish are feeding and you’re tangled you are fluffing around trying to make the cast then you need to get with it - you may just miss the best shot of the day.

Catchinf trout fly fishing in a flooded Tongariro river


Chris Dore is a battle tested fly fishing guide with over 15 years of professional guiding experience, battling the demanding, ever changing conditions that our New Zealand rivers throw at us.

In 2006 Chris became one of the first New Zealanders to successfully pass the internationally recognised Federation of Fly Fishers Certified Casting Instructors examination and has since taught many thousands of anglers to up their skillset.

For more in person and on river fly fishing advice and upskilling why not book Chris for a day or three?