If your bed is pooling, it ISN'T draining normally. MIght want to think about why that's happening. Your bed may be sitting on top of a clay layer. It may be necessary to do some re-excavating. That would be proactive. Was any excavation actually done, or did you just pile up soil on unexcavated ground?

Do you know how much rain you got? 3-4+ inches in one day? I would expect some puddles if the raised bed is walled-in with boarding which can hold the excess water in like a swimming pool, but it should drain away within an hour or so after it stops raining unless your situation is as Dan described.

There are so many factors. What did you fill up the bed with in the beginning? How deep is it? I What are the walls made of? Short of setting the bed inside a clay depression it should drain reasonably.

In any event you can always dig up the bed off season when hopefully mostly dry and mix in organic material.

My raised beds never ever have pooling, not once anywhere. I would suggest working sand into soil. I have watched it several times after HARD rain (3"-4" in an hour or two).

It's not what's under the bed, it's what's in it - do not get involved with the soil underneath the bed*. Especially do not mix any of the soil beneath the bed with the soil inside the bed - you have made a raised bed in the first place so as to provide a different situation than that provided by the existing soil on the level. Even if the raised bed is filled with the same soil that was already on the site the part inside the bed has been made different by being raised. And if puddles occur only after hours of heavy rain, do not remain for days afterward maybe nothing needs to be done - how have the plants been doing? Are you getting the desired response from them? Otherwise lightening materials like sand or perlite have to be added in large quantities in order to produce a textural change when clay and silt are part of the existing composition. Incorporation of organic matter in much quantity similarly produces a mushrooming effect (ballooning of involved soil volume), a particular problem when the soil being modified is within a confined or defined area like a raised bed. In addition it is undesirable for a garden soil to have an organic content above a comparatively small percentage at any one time.

So here’s lesson number one: Don’t add OM just because you think you need it. Too much OM creates overly rich conditions that can reduce the natural protective chemicals in vegetation. This means pests and diseases are more likely to be problems.

Why soil tests matter: lessons from my vegetable garden – The Garden Professors™

*If the entire garden site collects surface water to a nuisance extent the solution is installation of a drainage system

Fair point that in a raised bed that's a least a foot or so deep, it ought to be able to easlily absorb a few inches of rain before ponding is an issue. But if you've gotten a lot more rain than that, the bed will be saturated if there is no drainage below, and ponding will then happen. That's where what's under the bed becomes important. You might dig into the bed and see if the bed is, in fact, completely saturated. As in, mud all the way down. If so, you have a ground layer problem. If not, then the content of the bed itself is the issue, and sand and or perlite amendments are best. If a ground layer issue, then you have little choice but to dig out the underlayer better, and amend with something that will loosen the clay.

Water tables do not rise from below within beds and only within beds - planting mixes can be dumped on top of asphalt and rooftops and planted with success. Sand content of a soil has to become greater than 50% before a light soil is produced - if there is not already a quite significant percentage of sand present an enormous amount of sand has to be added in order to generate a noticeable change. And making a planted soil sandy can produce problems with droughtiness and leaching. Mechanical disturbance (cultivation, digging, turning over) of flooded or otherwise wet soils degrades soil tilth. Loosening of soils below planting level results in sinking of plantings as the soil so treated settles afterward. A small area dug out of a heavy soil prone to flooding and filled with coarse material is called a sump. Planting holes and small beds dug under similar circumstances including backfilling with a large enough component of soil texture modification materials to produce a markedly coarser texture also become collection points for water.

What is the soil in your raised bed? And if it's raining that hard, is there also water pooling up in other places of more natural ground around the neighborhood? If it's pooling on the ground, it's not that abnormal for it to do so in your bed while it's still raining. If you are having pooling after it's been done raining for a while, then you might need to address what the soil in your raised bed is made of.

What is your raised bed on? If it's on something very hard like a hard pack clay or an area that was compacted by machines or something big and heavy sitting like an old swimming pool spot, that can cause an issue because the raised beds can't drain into the ground properly.

If you have a raised bed, with walls, and an impermeable layer below, the water WILL NOT DRAIN. Nowhere for the water to go. If you don't have walls, then yes, the water permeating the bed will just run out the sides if the base is impermeable. So I guess a fair question is whether this bed has walls. If no walls, no question that the bed itself is at fault. That's true that fine sand is a poor way to make soil permeable. Coarse sand, like concrete sand, is better. I see no problem with digging flooded soil. When it dries out, you still have what you had before. You haven't taken anything away.

Water does drain considerably faster from a raised beds (RB) built on hard clay than the hard clay drains for 2 reasons, one of which has already been mentioned. 1) The added ht of the raised bed increases gravitational flow potential of the water column. That is to say the weight of the water column in the RB soil pushes down on water nearer the clay layer and forces it to move laterally through any openings in the sides, or under the sides if the rest directly on top of the clay layer. Stand a dry sponge on edge, then slowly start pouring water on top of the sponge. The sponge will absorb water to a given point (called field capacity), then water will start to flow laterally across the top of the surface the sponge is resting on. 2) Water's tendency to stick to itself (cohesion) and it's tendency to stick to other objects (like soil particles) added together + the force of capillary action, which in any soil which isn't saturated, pulls free water in all directions. The predominant direction is downward though, because the force of gravity will be working in concert with capillarity.

The first part of clay soils to dry is the soil exposed to the air. When the surface of the clay soil surrounding the RB dries, it dramatically increases the capillary pull of the dry soil due to the very large (collective) surface area of clay soil's particulates and the added force of adhesion the surface area causes. So you have the weight of the water column pushing downward and forcing water to move laterally, plus, you have water being pulled laterally by the soil's capillarity, significantly increasing evaporative water loss from the bed. As the soil surface dries, it continues to pull water from the RB.

When a RB is built on clay through which water is reluctant to percolate, it is best to avoid amending the clay soil on which the bed rests. This slows but doesn't stop 'the bathtub effect' from occurring over time. Raised beds, with their increased aeration and usually higher levels of OM, are hospitable harbors of refuge for populations of soil biota more concentrated than clay supports. Over time and through the activity of soil live, clay soils beneath RBs gradually become more porous and tend to hold more water in the root zone, so the beds would benefit from being moved from time to time.

The only reason I built raised beds it to keep things neat and make it easier to maintain the lawn around the beds. I'm fortunate that my raised beds are built on loamy soil that drains well, but I still see clear evidence of what I described in the paragraphs above, after I water with a soaker hose. Water runs out between the 4x4s that make up the bed walls and the soil around the beds becomes wet until it evaporates. The more impermeable the clay is, the wider the water spreads from the beds.

Al

If you're going to get ponding in raised beds then you might as well just amend your soil and grow in the soil. I've found that if I dig in 3" of manure or mushroom compost that my clay soil fluffs up till it's 8" higher than the original soil level so that it drains efficiently. If your soil has any slope this will add to the drainage. I think it's much less work and much cheaper to grow in the original soil and it's better for the earth as it's a permanent improvement to your soil.

I've been adding a shallow trench around a new bed by pushing my spade into the edge of the bed and rocking the spade toward the amended soil. I do this from outside the new bed. Any drainage now drains into the loose soil you just amended.

Sloping surfaces do not make wet soils dry, think of seeping embankments - it is the internal structure of involved soils that determine the drainage conditions therein. Incorporation of organic amendments does not produce a permanent improvement, for instance in a study undertaken in a hot summer climate peat dug into a soil could not be seen to be present one year later.

The whole point of a raised bed is to provide good drainage. If yours is not draining, there's something very wrong. Could we have more information of how this raised bed was constructed?

Embothrium

One of my gardening goals is to keep my soil from drying out. If one end of your garden bed is a foot higher than the other and your fluff it up 8" your position is that the bed won't drain.

At my age when I dig in 3 inches of mushroom compost I consider that permanent. My lawn which was converted to my garden has been a lawn for 70+ years and from looking at it it hasn't had any amendment during the entire period. I've mowed it for 17 years and always sprayed the grass clippings and some of the leaves that got dusted up with the mower but there's a 1/2 inch of sod and that's it. If someone had added that 3 inches a few times over those years I'm sure the soil would be much better. If I had a foot of loam soil I would add an inch of manure or mushroom compost every 5 years or so because it improves the soil

I don't think it's a good idea to tell garden folks not to add amendments cause it ain't permanent!

But organics aren't permanent. That's all there is to it. Bacterial and fungal action convert ALL organics to CO2. The time it takes depends on the particular organic. Leaves, with lots of hardy vascular tissue in veins, last the longest. No one tells gardeners not to add organics as amendments, but rather insist that they do so regularly. If when you mow the lawn and don't bag and remove the trimmings, as I do, you're adding organics to the soil. They in situ compost on the soil surface. In fact, it's pretty obvious to anyone with a compost pile that the pile disappears gradually as it ages. I mostly do leaf composting, but I have a separate pile for kitchen compost, and though we add a couple of pounds a week, it always amazes me that the pile size never really increases. In container plants, the soil level drops yearly. That's the organics disappearing.

This is what the soil in my raised beds looked like 2 years after I "made" the soil. It was mostly pine bark with a good measure of sand, Turface MVP, and reed/ sedge peat. While the soil itself was extremely productive, shrinkage was significant - about 1.5" (in ht) per year. Fortunately, I do 150-200 repots per year, mostly gritty mix, so I had a ready source of material to make up for the shrinkage. Over the last 20 years or so, the mineral fraction of the soil has steadily increased as I added Turface MVP and crushed granite every spring from the repots, so shrinkage has slowed a bunch, but the beds need more watering now.

If I had it to do over, I would have started with a load of sand/silt loam typical to the Saginaw River Valley) and added about 10% each of pine bark and reed/sedge peat and called it good. Still, it remains very productive.

Al

To the extent you don't want to excavate the underlayer, Turface as an amendment is a nice idea for standing water control. It's highly porous. Pretty much the same as under-car oil absorbant. At least as porous as perlite, and it's a lot cheaper. It is just clay, so when it dissolves it's probably impermeable, but it is supposed to have a lifetime of decades.

In my post yesterday about an alternative to growing in raised beds I was trying to say that if you grow in the ground the improvements become part of the soil; where alternatively what you put in the raised bed many times will become an effort to find a place to dump it. I also think it's much less work digging the ground as opposed to building the raised bed and finding something to fill it with.

I have had over 30 inches of rain in a 2 day period and water did not stand in my raised beds. 2 years ago I had 16 inches of rain one day, and 1 to 2 inches over the next 4 or 5 days and no rain standing in my raised beds. The ground around the raised beds were completed saturated, and any soil that had been tilled you could not stand on without sinking past your ankles. A picture would be nice, might help more than you would think.

If the sides of the raised beds are deeper than the top of the ground, it could cause water not to escape. Otherwise, there is probably too much clay in the raised beds, causing a clay layer that will not drain. Adding mulch to the top will not help, and I have no idea why someone would think adding a soaker hose to bed would improve drainage.

'If the sides of the raised beds are deeper than the top of the ground...'

This confuses me. By deeper, do you mean lower? That would not be a raised bed.

The sides can be just set on top of the ground. That is how most people put them in. Or you could dig down a few inches, and install the raised bed. A 2 foot raised bed could be put in the ground 6 inches, making it 6 inches in the ground and 18 inches above the ground.

Thank you for clarifying.

For me, the sort of raised bed I think is useful is one made in the garden, with garden soil (including homemade compost which has been well incorporated).

The soil is first dug, more soil is addled from elsewhere in the garden so that you now have quite a good depth of soil in the bed. This produces good drainage.

'Raised garden beds' - the sort I see for sale left and right around here - which are then filled with potting mix, are not my idea of a raised garden bed. Plus, I'd rather eat food that has been grown in (garden) soil than in potting mix.

"If I had it to do over, I would have started with a load of sand/silt loam typical to the Saginaw River Valley) and added about 10% each of pine bark and reed/sedge peat and called it good. Still, it remains very productive. "

Unless it's a small container and/or weight requirements are a factor, I too am a big fan of just mineral soil and some organic component. (for most applications, I use some flavor of sand or loamy sand)

I design a lot of soil profiles for general landscapes, bioswales/biofiltration, light weight rooftop applications, sports field root zones, etc. and one thing that I've learned over the years for deeper plantings is that, rather than placing organic amendment the entire depth, it can really help to do a "split layer" using the mineral soil / organic blend in the top 10 to 12 inches and just the mineral fraction without any organic below that. With less organic, you'll have less settling over time. And, since you're amending the top foot or so, that will be enough to provide a favorable rooting environment for a broad range of plants. This has the extra bonus of helping to avoid the formation of anaerobic conditions at lower depths when you've got deeper rooting species to worry about.

A few months ago, we had a lot of rain and received about 12 inches of precipitation. To prevent excess water from accumulating in my raised bed, I installed a drain. It has helped the excess water flow out of the bed and has been a great solution

seep holes help. My raised beds are concrete blocks (3 courses) with seep holes every coupla metres.

I have had no end of issues finding the right balance of soil mix - basically mineral topsoil with hydroleca/horticultural grit and an annual topdressing of composted bark does the trick for me.