Flooding Help

Hi,  I live in western Washington, Puget Sound area, where we get a lot of rain in the winter and at the bottom of my property we have some winter flooding.  The flooding is probably the worst it has been in the three years since we have lived here, some places is 3" deep of standing water.  I have attached a drawing of my property that shows the flooding area.  Right now some of the blueberries that I planted down there last year are sitting in water so I need to take some action quickly.  

The Eastern property line is a bit of a valley the neighbors property almost mirrors ours as far as elevation goes. They have run horses for many years and the soil is very compacted, they do have a drainage toward the bottom of their hill running south past our property, but we do still get some water from that side. We are also getting a lot of runoff from our hill.  We have pretty hard soil, my guess is mostly clay, under the first couple inches of soil.  The driveway runoff, and the roof run off is just pointed down the hill.  The pond overflow is on the south side I'm not sure where it leads to (I'm going to dig it up) but my guess is where it is currently flooding.

I'm thinking about digging a smaller pond in the North end of the flooding area, I would also like to put a couple swales on the hillside where I could divert the water coming from the driveway runoff and at least half of the roof water from the house.  

How would I figure out how big of a pond I should dig?  Our big pond is fed I believe by a natural spring.  Would the smaller pond be empty or low most of the year or also overflowing? Would diverting the pond overflow to a smaller pond, and slowing down the water runoff from the hill with swales be enough to keep the south side of the flood area from flooding? Also, I have marked on my drawing where we are planning on taking out some very large evergreens (I forgot to mark the stand of evergreens in the midst of the flood area that we are planning on taking out).  Will that make the flooding worse if we remove them?

I need some advice on how to drain this area and keep it from flooding in the future.  My plan is to put a food forest area along the South and East side of my property as well as 2 strips of food forest going from South to North in the hill on the Southeast quarter of the property where I can perhaps run pasture in between for grazing animals.  The flooding would keep a lot of this area unusable for at least half the year, plus I would have to plan for flood tolerant plantings.

I am open and hoping for suggestions, Thank you!

Just talked to my neighbor and he informed me that the pond overflow actually runs SE into the neighbors property, I'm guessing it ties into their field drainage.

A few questions;
- Does the flooding cause any damage?
- Why are the evergreens being cut down?
- Could you install a 20,000L tank on the house and reuse the rainfall? My signature has details of that.
- Water retention in the soil is great, can you run a spiked roller over the ground when its damp and work to improve the soil to a greater depth?
Pond Size at Northern end.
Measure the area being flooded, using 3 inches as the flood depth determine the volume of water being trapped.
That should be the minimum pond size you build.
Remember to keep topsoil aside to cover the earth after forming the pond.

No the flooding does not cause any damage as of yet, though I am worried about the blueberries being under water.  It is well away from any structures.
I am planning on cutting the evergreens so I can plant more edibles like nut trees, fruit trees and such like a small food forest or guild plantings.  That’s also why I want to dry it out a bit.  
I would like to have some rain catchment for roof runoff but it probably wouldn’t be that big like 4 rain barrels on the south.  I am thinking of diverting the runoff from the north side of the house into the swimming pool that I’m going to convert into a small pond though that only holds like 1,500 gallons. I would prefer to store more of our water in the ground like in swales, or maybe diverting to mulch pits or something.
For the pond size I believe it is about 270’x90’ it’s about 10’ on the South we have half of it on our property.

From this search I found some interesting answers
Blue berries and flooding
Berries and Floods

Utilizing proper soil drainage and irrigation techniques are important to growing healthy blueberry patches. Adequate soil drainage is essential for healthy blueberry patches. Blueberry plants will not tolerate excessive moisture (wet feet) for long periods.

Something I am not seeing is where does this water come from?  What have you tried that worked or didn't work?

At our other property, the land looked flat though it was actually a slow change in grade from other properties.  When it rains the water naturally washed across my property.  We solved our problem by creating a system of ditches and french drains.

While a pond might help your situation that seems like a lot of work for something that might be a short-term fix.

One of the things that attracted me to our property was the pond unfortunately it sits empty most of the year and only fills when it rains then it drains quickly.

Have you talked with someone about where would be the best place to locate a pond or if it would work for your situation?  In our state, the office is called soil conservation.

Anne Miller wrote:Something I am not seeing is where does this water come from?  What have you tried that worked or didn't work?

At our other property, the land looked flat though it was actually a slow change in grade from other properties.  When it rains the water naturally washed across my property.  We solved our problem by creating a system of ditches and french drains.

While a pond might help your situation that seems like a lot of work for something that might be a short-term fix.

One of the things that attracted me to our property was the pond unfortunately it sits empty most of the year and only fills when it rains then it drains quickly.

Have you talked with someone about where would be the best place to locate a pond or if it would work for your situation?  In our state, the office is called soil conservation.

So if you look at the map I attached on the original post I put contour lines on it (from county) and that flooding area is the low spot on our property so it makes sense that water makes its way there.  

We haven’t tried anything yet to fix this problem I’ve got some ideas I just am not sure they are worth it yet.  

Our pond stays full year round but in the summer it has dropped like 3’ in the past which is quite a lot for such a big pond (it’s about 10’ deep on our end). But that does lead me to wonder if our winter rains/snow may be just raising the water table here and that low area happens to be under it now.  If that’s the case is there any other option then just filling the low spot in with more dirt?

As for draining it I wouldn’t have anywhere to drain it to, unless my neighbor wants some extra water.  Really I would like to keep my water on my property just in a more contained way.

If the water is coming mostly from runoff of the hill, roof, and driveway maybe slowing it in swales on the hill will be enough?

If I dug a small pond there and the cause of the flooding is the water table rising it wouldn’t do much good, would it? I’m not sure.

I don't see well so I had not paid much attention to your drawing other than it is a nice drawing.

Looking more closely it looks like the lower elevation is below your garage.  I am not seeing where the flooding is.

I am puzzled by your last comment about draining the pond.  Why would you want to drain the pond?  Is that where the flooding comes from?

Its rare for the water table to rise above the ground in the manner you speak of.
Its my guess its runoff that accumulates at a low spot prior to soaking away.
Doing exactly what you actually want, keeping it in your soil.
Why not accept what is happening and let it e?

Anne Miller wrote:I don't see well so I had not paid much attention to your drawing other than it is a nice drawing.

Looking more closely it looks like the lower elevation is below your garage.  I am not seeing where the flooding is.

I am puzzled by your last comment about draining the pond.  Why would you want to drain the pond?  Is that where the flooding comes from?

Sorry the drawing is kind upside down sideways which doesn’t help reading it. The low point on the property is the SE corner South from the pond.

I mentioned draining not to drain the pond but you had said in your earlier post that you used French drains and trenches to remove the excess water from your property I was just pointing out if we put a drain down there there isn’t anywhere to drain it to.

John C Daley wrote:Its rare for the water table to rise above the ground in the manner you speak of.
Its my guess its runoff that accumulates at a low spot prior to soaking away.
Doing exactly what you actually want, keeping it in your soil.
Why not accept what is happening and let it e?

I may have to leave it as it is but the reason I wanted it not flooding is because I would like to plant some nuts and fruit down there that are not going to like sitting in water all winter and spring. Plus my blueberries that are already down there I would like to save.  Maybe it would be best to find a new spot for them and try to transplant them right away.

ok, please accept my quick MS paint drawing... but I have a few comments. If no building are being damaged by flooding, praise be. Flooding, of blueberries, I dunno, but, as a side note, Wa State Dept of Ecology has fined farms big on blueberry farms that have applied compost in fall that got washed off in flooding events and messed with their TMDL's. just something to keep aware of.  

I tend to think of land and plantings in places that plants want to be and thrive to grow. But that said, there are ways to manipulate water flow in a beneficial manor without changing the natural flow of things (keyline as an example of such).  US army corps of engineers had a big (disaster) plan to drain wet areas and river (straighten the rivers, drain the swamps) as fast as possible, huge problems there. Instead, beautify the land by slowing water at the top, help increase infiltration and percolation, delay the movement of water over the surface and create a path for water to move through the soil ... and that gets to my simple drawing.  You will likely need an engineer (or do a bit of search on web for a slope/contour/soil type/veg cover/rainfall intensity index model (sorry I dont have one off hand (MAYBE SOMEONE HAS A LINK TO SUCH A MODEL, RUSLE is a good place to start search))).

Another note, I'm pretty sure in one of sepp holtzers vids, ...to create a pond without permit, said something like ,,,you just take a little dirt at a time and make a small burm, then add a little more, if regulatory agency question, you just say "I was cleaning out a natural wet area"... I hope I got that right, full disclosure, I am not suggesting you do anything outside of permitting, and if I wrongly associated such comments with sepp, may I be struck with lightning.

So contour terraces. I have about a quarter acre of them, 2ft wide beds on about a 15% slope (1ft between beds), it works out well, you can angle them in a back and forth manor to prevent over flow kinda like a plinko game (?), plant the slope between each terrace with dense red clover or something perennial.

Ok, I think I should stop before I get in trouble. Have fun, but live life and be on the edge of trouble... the good side :)
P.  

one other note... nuts. Pecans are used quite often to "dry up" wet areas in the south, you might be able to find a suitable cultivar for your area.

Hmmmm. Ok, not what you want to hear, but something to consider: is there any example of swales on a hill making the area below drier?
As I understand Sepp’s system, all his earthwork improvements lead to year round ponds - he extends the time that wet areas are wet, not shortens it.
In Jeoff Lawton’s permaculture design course, he lectures on swales and says that an extensive hillside of swales can lead to a permanent swampy area at the bottom: by slowing the water, you have created a year round water source for the swamp. He didn’t consider this a drawback, as ponds and chinampas are some of the most productive spaces you can have.
And in making small farms work, Richard Perkins mentions that keyline plowing led to a ridge that was swampy later in the year - just from the plowing in a way that retains water.
If the area you are describing is under water for the winter and spring, systems that retain water uphill from that may not help you, may actually increase the length of time it is wet. At the least, I would try to find an example of permaculture water retention techniques drying out a downhill space, and understand why it worked. What was the catchment area? How much water was falling in a single event? During the whole rainy season? I suspect in you situation, at a low point where the water has no where to go and stays wet for half the year, your best bet might be to transplant the blueberries to uphill swales, and turn the low area into a pond or marsh.
I hope you update, would love to hear how things turn out!

Just saw the date on the previous post - hope to hear how this last year went!

I have no experience of ponds, but I used to live half way up a mountain, so we had a lot of runoff, the main idea was to just maintain the drainage in the correct places to let the water flow past us and onto the next lowest area, or into the nearest stream. It was an annual job, digging out the ditches before the main rains came. (or sometimes in the middle of the deluge lol).

We also planted big trees higher up, to stop the water that is falling. Big trees will suck it up.
Lower down we used reeds, and sedges, to make barriers or just to suck up water. Reeds and sedges also clean water, so they are useful if you are wanting to re-use the water.

I live in the same region (Whidbey Island) and experienced the same series of events this year:  Dry summer, wet winter, standing water in low areas of my new forest garden.  It's very slowly soaking in, but still way too wet for way too long for most of my forest garden plans.

Here's my theory and proposed fix:  Water is falling on the higher ground and not soaking in through the hardpan, which sits around 18".  The water flows down along the hardpan and accumulates in the low areas.  I'm going to break up the hardpan as much as I can with a 24" subsoiler, allowing water to more easily soak into the ground while also loosening the soil for the roots of our fruit trees (which are going in next spring).

This theory and/or fix may be wrong, in which case I'll dig two French drains to channel the winter water and deposit it off the lower end of the forest garden.  I'm trying the subsoiler method first simply because I want to loosen the soil for the new trees anyway, and hope the added drainage will obviate the French drains.

Being regional neighbors, perhaps there's some elements of my plan that may be useful for you if you have a similar hardpan soil profile.

Hi Kelli - I'm a water resources engineer in the Seattle region. I do the hydrologic and hydraulic analysis to evaluate the problems you're having. To understand where all of the water is coming from, I think gathering some more data (observations) would help.

Investigation/Observation
1. Have you checked NRCS Web Soil Survey to see the soil types for yours and your neighbor properties? Have you had any soil testing performed to categorize your soils? I would recommend digging a few test pits (or holes) around your property to better understand your subsoil situation and how that might affect infiltration rates.

2. Have you observed the groundwater levels during the winter and summer? Installing a simple piezometer (perforated vertical PVC pipe with an inspection cap on top) 4 feet deep would allow you to easily check your groundwater levels throughout the year.

3. How much hardscape (driveway, roof, outbuildings) is on your property relative to the undeveloped landscape? Even a small roof can contribute enough water to make other areas extra soggy.

4. Could this flooded area historically have been wetland prior to being converted to pasture/farmland/etc.?

Solutions?
Once you have a good understanding of where the water is coming from and why it wants to be there, the solution may appear.

In the name of, "the problem is the solution", perhaps you could grow plants that tolerate/love wet conditions. Ben Falk did this with his homestead in New Hampshire, when he realized growing rice made more sense than vegetables.

I like your idea of swales, because likely the issue is runoff collecting at the low point. If you can slow and infiltrate the water, you'll reduce the amount collected at the low point. That said, your soil data will tell you how helpful the swales will be at infiltrating the water they collect.

Large conifers (especially douglas firs) suck up a LOT of water. They also hold a LOT of water in their canopy during rain storms. If you remove the large conifers, you'll probably experience more water unless you implement other solutions.

Capturing runoff from your hardscape and structures will reduce the loading on the wet area.

The pond will hold water all year if the INFILTRATION + EVAPORATION < POND DEPTH. Temporary ponds also make excellent amphibian habitat, as they reduce predation by fish and are necessary for some amphibian life cycles.

I'm also in the PNW, Port Hadlock.  Though we're in the Olympic rain shadow, our property also floods at the bottom of a 7% slope.  Having more perennial vegetation in the higher elevations might help to keep and use water to reduce some runoff.  But as described, swales and small ponds, etc. above may just prolong retention below.  Instead, I would dig out deeper but also smaller vernal ponds in your flooded areas with higher ground between them, in which you can plant bushes and trees that can tolerate wet feet but not be covered in water (e.g. bog cranberry, high bush cranberry, aronia berry,  keystone willows). Those plants can then use the subsoil water during our dry periods.  Having longer lasting vernal pools will also be a boon for amphibians - frogs and salamanders in our region who definitely need our help, as well as other wildlife - birds, insects, etc. The vernal ponds will need to last for a while until the tadpoles mature.  With GW, our wet/dry seasons in the Puget Sound area might become more extreme, so now's a good time to adapt our landscapes to possible changes.

I don't know what the requirements are for your area but in my Western Washington area any land development that disturbs more than 7000 sqft of land or involves removing vegetation form areas that disperse runoff from driveways or roofs would require a permit.  That would likely involve hiring an engineer to either meet the prescriptive requirements of an 1100 page design manual or do a detailed computer model analysis.  However, since your roof runoff is just aimed downhill it sounds like your property has never had to meet such requirements.  

Your roof drains seem to just end in an open area.  There should be some sort of splash block or rock pad at the end of those drains to disperse the flow and then to prevent downhill runoff that open area should be 100 to 200 feet of native vegetated flow path.  I suspect that is contributing to the wet area below.  The prescriptive method to fix that would be to break up the soil to an 18 inch depth; mix in a lot of compost; plant with native trees, shrubs and groundcover and cover with mulch following a down slope line from the drain ends.  

You didn't mention what the deeper soil conditions are.  The several feet of water that falls on your impervious areas each year has to end up somewhere.  Diverting it onto your neighbors property is usually not allowed.  If your soil can't infiltrate it then it will pool at the surface.  Is your road is acting like a berm to retain the water but occasionally spills over?  If so adding more soil might just make more mud and make the road worse.  Maybe you could turn the southern part of the wet area into a rain garden that would better infiltrate the water.  You might be able to shift some soil around while building that.  

Ok, this appears to be an older thread, but one that appears to be garnering some interest.  Background - spent around 20 years in excavation/light engineering; 10 years in soils engineering and geotechnical; 25 years in flood mitigation, flood identification/mapping and assisting on development/review of flood mitigation projects.

First need would be a larger map to show the context of the property in question.  It is very hard to know what to fix without information.  That includes the NRCS soils mapping info that an earlier responder suggested is invaluable.  The soil types often identify if the soils are wetland or not as well as the average slope.  In that area of the country, you probably had continental glaciers.  The soils would then be what I was taught 50 years ago would be diamicton or essentially whatever was in the ice when it stopped moving and melted.  Often if the soil is clayey, it will be locally called "hardpan" and it can be amazingly hard and nonporous.  The suggestion to subsoil is excellent for far more than just water infiltration.  It will allow more oxygen into the subsoil to enhance soil biota and that is the cheapest and most efficient way to enhance soil structure for growing plants.  I would say, move the berries from the wet area, I have a section of road ditch that cannot get standing water but still is too wet for some plants.  Willows, dogwood, wetland flowers and such are great to plant.  The flowers will pull pollinators and beneficials.  Standing water is usually not a good thing due to potential for gnats and mosquitos.  If you can get a large enough population of amphibians, that is not such an issue.  For gnats, plant flowers that humming birds will access.  They eat tons of gnats to get the protein they need to be healthy.  

Your septic system is on a good grade, but I do not believe there is clear identification of whether the drainage is dry well, stone fill or leach field.  With the gradient your contours showed, that could easily provide much of the water pooling at the low point.  Ground water follows the general slope but often that slope can drop faster than the water table surface and that leads to wet weather springs.  The picture seems to show standing water along the drive.  That is a concern.  Not only can heavy precipitation lead to overtopping, a saturated road bed will be unable to handle heavier vehicles or tractors, leading to rutting and, if someone attempted to pave the wet area, cracking known in the road industry as "alligatoring" due to the similarity with a reptile's back.  I doubt you have much frost, but saturated soil with frost will create seasonal issues of poor road surface.  I have seen a drive roll like waves on the ocean under a travel bus during frost out.  We were all walking to lighten the load until the bus hit the paved road.  That road almost scrubbed the bottom of the bus it rolled so deeply.  If the wheels had broken through, we would have been waiting for a very heavy wrecker for some time.  If you do wish to pave over a wet section, use layers of geotextile and stone as a base.  The geotextile will create a pad to spread the weight over a larger area and keep the stone from being contaminated by clay and silt squirting up from the wetter area below.  If that happens, you will be dumping stone until the cows come home.

You did not identify if you have slab on grade, crawlspace or basement.  If crawlspace or basement, it will be vital to move any runoff from uphill around the foundation to storage (hopefully) or to allow to drain downhill.  Otherwise, in a wet situation, open water can collect in either basement or crawlspace and that is an invitation to mold and fungus growth, much of which can be downright unhealthy.  If drains were run from beneath the house site, they may well have been routed into the leach system from the septic.  Don't laugh, I have seen floor drains run under septic tanks into the same drainage as the septic.  Just luck that no backflow  to the cellar occurred.

Also noted above, ensure you have checked with any zoning or building codes for drains.  I read that horses were being kept on the other side of the property line with some pasture about the same elevation as the lower wet area.  Be careful if keeping the entire area wetter.  Horse lovers get very protective if they feel the ground is too soft because someone build a pond near their pastures.  Some breeds of horse have very fragile leg bones.  Hopefully there are no cattle there.  If the neighbors decided to raise some beef or dairy cattle, cattle instinctively relieve themselves if they walk into a pool.  That could create multiple issues with having open water down there.  One way to counter open water would be to push top soil back, get coarse stone or gravel dumped, encase with geotextile and then recover with top soil.  Then the stone pile would maintain lots of porosity and serve as a great water retention area not subject to drought or mosquito growth.  Any trees with tap root growth habits planted on top will send down shoots and, once they are well established may nurture other trees that share the same fungal types.  Groundbreaking work on how fungi link multiple species of trees into a living web in forests indicate the evergreens you are planning to cut may be worth more alive and nurturing the area.  Check the work of Canadian researcher Suzanne Simard, her work has revolutionized our view of how fungi work to link living organisms and to assist each other to respond to attack from both natural and human sources.  Properly implemented, the natural systems are much more resilient to environmental stress.

Hope this is helpful.

Hi! Im in Portland and have been inundated with rain as well. I am still a novice but in case it’s helpful I’ve attached a few videos of my situation. The first is where the water comes from since a lot of people asked about that. Mine just pops out of the ground during big rains. Never in the same spot, but in the same general area. So I built some swales downhill from that area (video 2). As you can see, two are holding strong and the middle one is a disaster. I’ll build it up and plant it like crazy when the water recedes.

One thing I’ve learned about my own property in 3 winters is that I get too much water to capture. A lot of the information I’ve read over the years is from Australia or the US Southwest where they capture every drop. That’s just not going to happen on this property. So my swales might be described more like switchbacks where the water is captured during small rains, but is allowed to run like a river during big rains. I think I’ll always be adjusting and playing with it… I love making changes in the fall and then anxiously awaiting the winter rains so I can see if it works. Helps me look forward to a season that is otherwise not my fav.

**I can’t figure out how to post a video so I attached screenshots instead.

Fungi understanding as well as soil biologicals are very important. Not immediately so be patient. Subsoiling is very short lived and may not be worth the expense. Organic material on the soil surface is critical to feed the soil life.
The earth worms are the soil drainage workers. Worms need oxygen so they will not be the key in the flooded area. But they will give you the benefit of infiltration from the high area to the ware edges. Each year The flooded areas will decrease

Each area of the country has different challenges.  I could not tell what slope you have, so my response should be taken with with care.  The photo of water welling up out of the ground along with the information that the seeps seem to move around would make me suspicious that some subsurface burrowing is happening.  In my area, we have woodchucks, in the west, prairie dogs and ground squirrels are found.  All will create burrow networks that can redirect wet weather water.  In the Swiss Alps, I remember a study that showed how ground rodents created shallow burrows that pulled flow off the surface and moved water far faster just below the surface than is normal for subsurface water to flow.  Most burrowers will create bypass passages to leave them safe in their inner chambers while the water runs alongside.  I would counsel keeping an eye on any such burrowers and if you have issues with their passages (really bad for larger herbivores and potential killers for horses), see if you can use biologics to redirect their area of activity.  Many of them do not like certain plants due to the chemical weapons those plants produce.  Another potential issue is if ground bees take over old burrows.  Nothing creates a buzzkill like stepping into a large ground bee nest.  It can mess up your whole day.

Good luck.

Roger - In your part of the world, I would agree that subsoiling may not last long.  Much of Iowa is old prairie and the upper soil was created by windblown soil and is very loamy.  That soil is not very high in clay.  In my part of the Northeast US, we have soils dropped and occasionally pounded down by mile+ thick glaciers.  We see clay around boulders and rocks of all sizes.  My back lot is only a couple of feet of soil above shale bedrock from over 350 Million years ago.  So, for my soil, subsoiling will carve grooves in thin bedded shale along the bottom and will let oxygen feed the soil organisms.  It also brings nutrients back to the surface.  We get deep frost that also helps to pack soil tightly.  I have a decent slope on my back lot where my neighbor's cattle graze.  I have watched their wandering pack the soil like concrete.  After a few years, I now have wet springs on the side hill where I have nearly lost my boots.  I need to subsoil that ground to allow the water to move downhill to my pond and to keep the cattle from mucking the ground to a consistency where grass will have a difficult time growing.  I would love to have some Iowa topsoil.  But, each of us has to make do with what we have to work with.  Until I can amend the back 40, I will have to keep subsoiling for multiple reasons.  

The PNW and BC where I am was essentially rainforest, and is now cities, towns and farms.

As mentioned, remove the evergreens with care, they are soaking up a tremendous amount of water.

I too have a high water table; looking at the flood zone maps for my area was very revealing; there is a spring fed lake a couple of miles away, the outlet for that lake has been "interupted" by multiple roads and areas where the land was built up and essentially buried the outflow.  With careful attention it is clear that the outlet used to run behind out property, and magically reappears at the end of our street in a culvert/storm drain system that the ditches run into, then down to the river.  

This means our property is essentially fill on what would have been a marsh or wetland.  The good news is that in summer, a five foot deep, hand dug well remains useful all summer long.  The bad news is that in winter, when we have heavy rains we will have standing water, at times inches deep, and literally running like a river, obviously trying to access the old water course behind our property (that no longer exists).

Your situation sounds similar to ours.  To my mind we have two options provide a place for the water to flow and exit the property and/or elevate the land by adding rock and soil.  As to the legalities of your situation, sounds like there is a local land/water guru above who might have all the answers you need.  Here we are working to divert water from the water logged areas by burying perforated pipes (leading to ditches) under gravel and then topping with soil and retaining the lot with metal roofing panels so we end up with raised beds.  This eliminates the plants floating in water in the wet season, but allows them put down deep roots for water in the summer.  We are also propagating willow shoots from our huge tree for use in other areas.

Any chance the evergreens can stay at least until the nut trees are established and doing their part drinking up the excess water?

As a follow-up to my post last year in this thread, here's our results (and a remimder, we're on Whidbey Is., not far from the topic creator):

We cleared all the trees from the upper end of our property, removed 1/2 the stumps, subsoiled 24", and topped the ground with 40 yards of 1/2 composted wood chips (over an area of 5000 sqft).  We also added a rain collection (diversion, really) from our small barn, removing 600 sqft of rainfall area.

Rainfall this year has been less than last year, but not to a striking degree.  Still, we've had essentially no drainage issues this year.  Last year we were bogged down into June.  This year, nadda.

So was it the subsoiling?  The wood chips?  The reduction of rainfall?  I don't know.  I do know I am going to continue these tactics.

I was personally very surprised that after removing dozens of large trees, our drainage improved.  I was afraid it might go the other way.  Pleasantly surprised!

And I must respectfully disagree with the comment above about subsoiling being a temporary fix.  Hardpans grow on geological timescales.  If you subsoil through it, it will not return on any timescale that matters.  I personally think it was the most important thing we did, but that is just an opinion.