River Hazards: What Are Strainers On A River?

Low-head dams might’ve earned the nickname “drowning machine,” but don’t assume that other river hazards, such as strainers, are any less deadly.

What are strainers on a river, though? Why do they rank so high on the list of kayakers’ worst nightmares? And, most importantly, how can you encounter this deadly blockage and live to tell the tale?

Keep reading to find out! 

What Are Strainers On A River?

Strainer on a River

River strainers are created by obstructions – naturally formed or man-made objects – that allow water to pass through but “catch” larger objects, pinning them in place. In essence, they will strain the river of debris, boats, animals, and people, by “filtering” the water through the gaps in the obstruction – hence the name.

The best way to think about a strainer is – well, a strainer. As in, the one you have sitting in your kitchen as we speak.

As silly as the comparison might sound if you think about it, there isn’t that big of a difference in how a river strainer and your average colander work:

It allows water to escape through the gaps, but the openings aren’t big enough for larger objects to pass through. It’s like when you’re draining pasta, and the water runs out – but the spaghetti remains inside the colander.

Strainers can be caused by many things and can occur naturally or due to artificial obstructions, especially during flooding and heavy rain. Anything that can form a barrier on the river while still letting water pass through could create a potentially deadly trap known as a strainer.

Here are some examples of strainer-forming obstacles you might encounter as a kayaker:

  • Fallen trees
  • Large branches
  • Root systems
  • Logs and boulders
  • Tires
  • Submerged vehicles
  • Fencing
  • Guard rails
  • Construction debris
  • Shopping carts

Unfortunately, our waterways have become a dumping ground for debris and waste of all sorts – and it’s essential to understand that this is more than just an environmental risk. There’s always a possibility of these larger objects forming deadly river obstacles, too. 

What Is A Sweeper & How Are They Different?

Sweepers can sometimes accompany strainers, which makes the whole thing even trickier. So, it’s essential to know the difference and learn how to recognize both when you encounter them on the river – preferably before you get too close. 

Unlike strainers formed by underwater – and often “hidden” – obstacles, a sweeper is created by overhanging barriers, like a fallen tree or low-hanging branches. 

That’s the most significant difference between the two. 

Sweepers and Strainers

So, yes, sweepers are generally easier to spot, but that doesn’t make them any less dangerous. There might be a portion of the obstacle you don’t see, like roots and branches, hiding under the surface and forming a strainer.

Talk about double trouble, huh? 

What Is The Danger Of A Strainer?

Strainer and Sweeper in River

Strainers can be extremely dangerous and force to be reckoned with; I hope I made that part clear by now.

But what is the danger of a strainer, exactly?

The single most significant risk associated with strainers is the risk of entrapment. It’s not the obstacle itself that’s deadly, though; it’s the relentless current passing through it.

Due to how strainers work – by letting water pass through while trapping larger objects – there’s a real risk of getting pinned against the obstacle, held in place by the sheer force of water.

Kayaker stuck In Tree Strainer

Worse yet, the current can be so powerful that it flips the kayak over and pins you against the barrier, immobilizing you and pulling you under. Once you’re under, fighting the water pressure becomes virtually impossible, making drowning due to underwater entrapment a probable outcome.

Even if you manage to avoid entrapment, getting wet could be a risk in itself, depending on the weather and water temperature. Cold shock and hypothermia can be every bit as deadly as the strainer you’re trying to avoid. 

What To Do If You’re Approaching A Strainer?

Man and women on river bank, portering around river hazards

If river kayaking is your thing, you’ll eventually come across a strainer. It might happen sooner or later, but I’d say that the encounter is pretty much inevitable.

With that in mind, I probably don’t have to tell you how vital it is that you know what to do when approaching a strainer, do I?

Now, when it comes to river hazards like strainers and low-head dams, kayakers generally have to stick to the same safety rules – with the number one rule being:

Avoid them.

But since strainers tend to hide underneath the surface, spotting this hazard in advance isn’t always an easy thing to do. A few twigs bouncing on the water’s surface will often be your only indicator of what’s underneath, and even then, you only see the tip of the iceberg.

So, I’d like to add three more rules to that list:

  • Plan your route. Do your research, check the weather, watch the water conditions, and scout your route before launching your kayak; do whatever you need to do to familiarize yourself with the area and identify potential hazards ahead of time.
  • Keep a safe distance. The best possible scenario is one where you spot the strainer in time so that you can maintain your distance and navigate your way to the nearest bank.
  • Portage around it when possible. If there’s no way to navigate your way around the obstacle safely, the safest course of action would be to paddle to shore and portage around it.

Keep these rules in mind at all times; they might save your life one day. 

Oh, and while we’re at it, here’s what to do if you capsize as you’re approaching a strainer and there’s no way to reach the shore in time:

Start swimming as if your life depends on it – because it does.

But contrary to what your instincts tell you, if there’s no way to avoid the obstacle, you should swim towards it as aggressively as possible rather than scrambling to escape.

That’s right; towards it.

Be RiverSafe - Survival swimming - Strainer swim

Take control of the situation by swimming directly at the strainer full force and putting all your energy into propelling your body up and over the barrier. Survival swimming is your best shot.

Bonus Advice: What To Do If You Get Caught In A Strainer

Kayaker suck in river strainer

No one wants to think about getting caught in a filter-like obstacle on the river; it’s a kayaker’s worst nightmare. But it’s important to discuss this scenario – as uncomfortable and scary as it might be.

Hopefully, it won’t get to that.

But before you leave, I’d like to go over some additional tips and safety advice for good measure:

  • Always wear a life jacket. I am sure it goes without saying, and is just common sense, that a life jacket is one of the most important pieces of safety equipment you can have when kayaking – regardless of your swimming ability or skill level. In fact, in many parts of the world it’s a legal requirement, and if you encounter a river strainer it might just save your life.
  • Don’t kayak alone. Kayaking in a group is generally safer because you can all keep an eye out for each other, scout the waters more efficiently, and alert each other about potential hazards. Plus, having others around means you’ll have someone to help with the rope-assisted rescue.
  • Perform a wet exit and swim to shore. If there’s no one around to help, perform a wet exit, get over the obstacle, and swim to safety. It’s not ideal, but it might be your only way out.
  • Always keep an un-pin kit onboard. The so-called rescue gear or un-pin kit, consisting of a throw bag with rope, an inflatable Type IV throwable PDF, standard and locking D carabiners, pulleys, and Prusik cord – an essential product that should be a standard part of your gear. It will be vital for whitewater rescue and scenarios where the kayak is pinned against an obstacle in the water.
  • Complete swiftwater rescue training. Attempting to rescue someone who’s caught in a strainer is never a simple task. Proper training is a must. Otherwise, you could end up endangering others – including yourself – in the process. 

Once you’re caught in a strainer, there’s not much you can do besides fighting to get over and away from it. But hopefully, the tips I discussed above – along with a suitable PFD and a helmet – will be enough to keep you alive and well. 

Strainers & Kayaking – A Quick Summary

You came here in search of an answer to a relatively simple question – what are strainers on a river, but I hope you’ve learned a lot more than that.

Again, the number one thing to take away from all this is that you should avoid river hazards as much as possible. Prevention is always your best bet.

Know the river you’re paddling in, stay aware of your surroundings, and keep a safe distance.

But if things don’t go as planned and you end up caught in a strainer, your PFD, your paddling group – and, preferably, at least one person with swiftwater rescue training – and an unpin kit will be your best friends.