Recent Flooding, yesterday 3.5" in a couple hrs.

[SPIKER]

Well had a pretty good gully-washer yesterday, took a few hundred yards of gravel out of the normally low to no flow creek and left it all over my grass/yard areas again. 3 years ago it did it 3 times in 2 weeks, so far this is only 5th flash flood like this her in 15 years. The creek flows maybe 2/3's year less than 4"wide x 1" deep but any time we get Heavy Rains it drains few hundred acres and one pond... This flash flood left a lot of bluegills dead from getting washed out of the pond. The thing drops a lot of debris into my from bridge to culvert conversion I was procrastinating on. I had culverts welded up and pulled under the bridge and chained to the bridge. The flash flood washed up some logs and clogged the culverts & wrecked a lot of what I had DONE. Spent 6 or 7 hrs FIXING all that today.

Culvert (24' cut in two and galv pipe SAFELY welded the two together. (NOTE Welding on Galvanized stuff is dangerous, you need fresh air system.)


click pics for full size & see all photos in the gallery on PB.

this was a week or so ago after a pretty good rain but normally what it looked like above the bridge/culverts.


After cleaning up a bunch of the gravel, same area as above only slightly to left.




Looking back at bridge and culverts after flood



Looking down stream from bridge normally way it looks


after flooding

the fixed culvert under bridge and some back filled w flood gravel out of yard.



some of the bedrock washed lose about 3'x3' size.


center 8" pipe washed 200 yards down stream from where I HAD it and the waste high grasses all washed flat.

looking back towards the bridge area 200 yards away


Saturday spent on tractor priceless. lol

Mark

 

[Bird]

I can't even remember the last time we had enough rain to produce any flooding.

 

[redman135]

Your pipes are to small for more than regular floods. You need much larger pipes or to lower you track to allow large floods to bypass the culverts without wrecking the crossing. I have used this tactic to prevent damage/scouring around my bridge .

 

[EddieWalker]

Is that a bridge over your culverts? Why do you have culverts under a bridge?

Eddie

 

[weldingisfun]

It looks like it is time to turn that into a low water crossing. Leave the culverts in place for normal flow and dig 18" footers on both sides and cover it all over with 4" of concrete. When you get your floods it will go through the culverts and up over the top without washing out your crossing. Or, at least that is what is supposed to happen, Mother Nature may have other plans.

 

[Gary Fowler]

Looks like you need to fix the culverts by replacing the gravel fill and then pouring a concrete header on both upstream and downstream and cap on top. This would keep the gravel from washing away during floods AND allow overflow to pass over the top without damaging the roadway. Be sure to make the header embedded in the dirt far enough so that rushing water doesn't undercut it. On a compacted gravel base, it wouldn't need to be over 3" thick but would allow most of the flood water to simply run over the culvert tops without washing anything out.
Remove that bridge that would trap trash washed out from upstream.

Another thing you might want to consider is just taking out the culverts and putting in a low water crossing of concrete. If you don't have to access the other side during the flood stage, this would be much better than trying to size a culvert to accommodate any amount of flooding.

 

[SPIKER]

Sorry my post wasn't clear the culverts are REPLACING the bridge and the project is just getting started..

They are 24" and I welded 1" galv pipe holding them together ~6" apart in the center. Then I slid PVC 8" in between them from the down stream side UP just for more flow and probably will carry 90% of the normal flow. The "creek" does go DRY about July/Aug most years for a week or two at a time (maybe more) depending on rains.

I have lots of LARGE boulders/rocks that will cap both sides prior to being done & where the bridge/culverts are is actually a bit higher than place water can flood around it. It is set with s bend just above the bridge that has eroded away a bit so some of the boulders will be placed to slow/prevent this from being an ongoing issue.

My biggest issue will be logs/branches clogging them up. I tend to keep the creek bed free of these under normal cases & I control abut 80% of this dryish creek. Neighbor with the farm pond has about 400 yards worth of woods & OLD dam as this used to be a series of ponds at some point. It is used to access about 17~18 of my 22 acres of woods/land so have to keep something there.

The Bridge was built prior to my buying the property & is made from frame of a old mobile home with Telephone Poles lag bolted to the main metal beams. The metal is getting pretty soft from corrosion over the years & poles also getting soft. The deck is shot as well & to replace the deck would cost as much as the culverts & would be done in a few years if/when the metal is gone. The bridge metal & poles are staying but gravel will be leveled up to the OLD deck height so some erosion of gravel would be only a maintenance fix. The metal/poles will keep overall problem floods from going very far into the road surface.

This pic shows the flow of what happens, look at the grass in bottom left corner. The photo is pretty LEVEL vs LAND SLOPE & bridge/culverts are higher by a foot or so at the right vs left of bridge (photo perspective.)


The low spot the flood would go over is grass & would only have over flow water & should not damage much in the rare times this could happen. We normally only get steady rains the 3.5" in couple hours is a LOT for this area... I mow that area and is plenty wide & only concern would be sand/gavel building up in front of the culverts which I can clean out with the tractor & backhoe on those rare occasions.

Edit in also note the current FLOW in the creek is probably 20 times the average "Flow Rate" of the creek under normal conditions. Normally flow is 1 or 2 inches deep after a regular rain by maybe 10~20 inches wide in level areas. At spots it is less than 6" wide by inch or two deep & the 8" PVC could handle normal flow 40 weeks of the year.

Mark

 

[SPIKER]

Have not added any more pics but Monday/Tuesday we had couple more inches of rain in a few hrs and everything flowed great without flooding/backup issues. The ground is still too wet to use the tractor without sinking into the axles but will get more back fill under the bridge and make it work well...


Mark

 

[SPIKER]

Well today I did a bit of looking and took most of the time to mow but enough to take a few sec of poor quality video of the stream flowing it's normal flow rate for spring time... The flood from 2 weeks ago dumped an un official 3.5" in an hour and 6" for the day of the flood. A bunch of videos and photos on FB from my neighbors phone (new smart phone so video is better.) I'll try and get a copy on here or link to it.
as always thumbnails to see full size click the pic/vid.

pic of the inlet (notice the 24" inlets are not even taking any flow thru them.)



Inlet side


and outlet side. Notice 95% of flow rate is thru the 8" pipe and or seeping thru the gravel



Mark

Edit in :

Pics from my Neighbors phone of the day of the rain. see if these work...
Rain flooding above ground pool overflow from 24' pool.
https://scontent-b-lga.xx.fbcdn.net...753_861636187198059_7972933016098202855_n.jpg

and the rain off the road crossing the drive.
https://fbcdn-sphotos-f-a.akamaihd....485_861636150531396_3432333661548807125_n.jpg

 

[Stimw]

Here in Florida we call 3.5" of rain a Summer Afternoon!