constructing ditches 4

[lancekilgore]

Hello all, new here.

I have a question I have bad flooding and I tried building a ditch 1 foot wide by 2 feeet deep filled with river rocks. That did not work the rocks filled with dirt. So I am in the process of removing the rocks. I will still have the ditch that is 1 by 2 feet deep. My question is what can I do to the dicth to keep the dirt from washing awayand getting bigger and out of control?? I thought about concrete but to expensive, I thought about lining the sides with wood but that would only last so long. Are there any solutions for me out there?? Not to expensive please.

 

[Maury]

Can you line the sides and bottom with the rocks? If the flooding is intermittent, sod or seeding could be enough. What longitudinal slope do you have?

 

[cvg]

First - you should always place a filter fabric under the rock. this prevents the fine soil under the rock from being washed away.

Second - It sounds as if you may have sediment which was deposited in your channel which then covers the rocks. You need to either remove the sediment before it gets into your ditch, or make sure it moves downstream and doesn't stay in your ditch.

To remove the sediment, you construct a sediment basin which is basin excavated upstream of your channel which is designed to fill up with sediment. It must be cleaned out periodically.

To keep the sediment moving through the ditch, make sure you have a good slope and sufficient capacity in your ditch, so the water velocity is high enough. this will keep the sediment in suspension.

 

[francesca]

It is possible that the sediment is coming from off your site, and your rocks are dissipating enough energy to make it fall out of the water and accumulate in your ditch.

If this is the case, then somebody upstream is in violation of the NPDES permit, and has is legally responsible.

How long has the flooding condition persisted? Is it new? It could be that construction activity upstream has caused more water to cross your site, which also has legal ramifications.

Sediment moving through the ditch is a bad idea: the sediment needs to be contained upstream of the ditch, not downstream of it. The only sediment concerns the ditch should have is not to cause any more sedimentation.

Ideally, you need an indication of the size of the drainage area, an indication of the ground cover in the drainage area, and the slope of the ditch, and a geographic location. These four things will enable a crude calculation of the amount of water flowing in the ditch, as well as the depth of flow in the ditch. This way, we'll know if the ditch is adequate. This will also give an indication of what type of protection you need on the ditch to prevent erosion in the ditch.

Failing this drainage area information, the size and slope of any upstream pipe would give a big hint.

Vegetation (i.e. grass) is usually adequate protection - once its established - for flows between 3 and 5 foot per second. Anything faster and you'll need those river rocks to dissipate energy and protect the ground below the rocks. If the slope is steeper than 10H:1V (i.e. 10%), then you definitely need to consider a liner below the rocks.

Do the rocks actually fill the ditch? Or just line it? How big are they, on average?

 

[lancekilgore]

the edges of the ditch are straight up and down, where do I get the filter fabric, to put under the rocks? I have seen it in Belgium, Korea, and Germany but not here? The flooding only happens about five to six times a year during heavy rains. It washes my road out when it does so I paved the road and now it is eating the dirt away under the road. Yes the rocks are filled all the way to the top is this a mistake?
Should I slop the sides so I can plant grass and rocks?

Thnanks for the replies

 

[cvg]

It sounds like you have constructed a french drain when you really need an open ditch.

Flatten the sides of the ditch so the top of the ditch is about six or seven feet wide. Bottom width is 1 foot and depth is 2 feet. This will provide a slope flat enough so the rocks will stay in place on the sides of the ditch.

Then place the filter fabric on the bottom and rocks on top of the fabric. You can get the fabric at Home Depot or Lowes in the garden department.

You could use the rocks you have and just line the bottom of the ditch. Then use grass for the top part of the ditch.

 

[francesca]

If the flooding is happening with that kind of frequency, then you'll find extreme flooding every couple of years. Urban storm water systems are usually designed on a "10-year occurance storm", or a storm so big, it has a probability of occuring only once every ten years. Provided that flooding will not affect your buildings or vehicles, however, this shouldn't be a problem.

Filling the ditch with rocks is a mistake, because the rocks are taking up room that the water would flow in. If there are smaller rocks, these will help prevent the bottom eroding, providing the flow isn't too great or the slope of the ditch isn't too steep.

Sloping the sides of the ditch is highly advisable. Vegetation can't regrow on sheer slopes on your ditch, which means that they'll erode every time it rains, making your ditch wider over time.

Our typical ditch section is 2' deep with sides sloping no steeper than 3H:1V (33%). Depending on where you live, you might want to mow the grass on the sides of your ditch, and if you have space, a gently sloping side slope will give more room for your water to flow, as well as slow it down (more friction and less depth contributing to momentum).

Where are you located? How long is your ditch? How steep is it? Where is the water coming from and where is it going to?

It concerns me that the spaces between the rocks are filling with sediment. Is this sediment coming from within your ditch? (For instance, did it wash in there from the pile of dirt you excavated to create your ditch?) Or is it coming from off your property?

If this sediment is washing off your property, and it's of your making, you could be liable for a fine or a lawsuit. If it's washing across your property from somebody else's property, then they could be liable for a fine or a lawsuit.

 

[lancekilgore]

looks like I will get the erosion fabric from home depot and angle the ditch with rocks on the botton and plant grass on the sides of the ditch. I live on the plains out side of Colorado springs. these floods have been happening since the don of time. we are also in a new housing development, not a part of any city. so the water comes off the hill above and into the premade ditches that eventually goes to this big depression to hold the water in the middle of the development. my little ditch about 50 feet long is only there to catch the water from washing out the or my road and devert it to the big ditches at the end of the drive.

Thanks for all the help.
Lance

 

[cvg]

You may want to discuss this issue with the developer and also with the County development services department - who presumably reviewed and approved the grading plan by your developer. Management of the offsite flows and sediment should have been addressed in the engineers report and implemented by the developer. This shouldn't have been your responsibility. As mentioned previously, this is a NPDES issue and it appears that your ditch may continue to fill with sediment if there is no sediment trap upstream of your house.

 

[francesca]

I work in residential subdivision design, and can assure you that a housing development on previously undeveloped land increases the flow of water off site, unless adequate measures are put into place. Even if your home is part of the first phase, construction of subsequent phases should not negatively impact you, for instance, by flooding your front yard.

Our standard detail for rock lined ditches (called "rip rap" ditches does not call for a fabric underneath the rock. You are obviously better off with it, but it may not be necessary. The crunch will be where the sediment is coming from. If it's coming from upstream, then you more than likely don't need to go to the trouble of unpacking all your rocks and putting down the fabric. If, however, the sediment is coming from your own ditch eroding, then I would recommend it.

As mentioned above, even out in the county, there will be some regulatory body (somebody owns the public road, probably a "county highway authority"). You should contact them regarding the sediment and the flooding -- which could be separate issues. They are responsible for road and drainage issues because they accepted the road and drainage structures from the developer. You should not have had to go to the expense of creating your own ditch; the drainage provisions ought to have been adequate.

The following document outlines the Colorado NPDES permit, and the responsibilities of developers and their contractors. If the sediment is from construction activity, call the appropriate person at the state and they will require the contractor to clean up your ditch at a minimum.

http://www.cdphe.state.co.us/hm/PCD/water/appc.pdf

These are the people you can contact at the state.

http://www.cdphe.state.co.us/wq/wqhom.asp

Good luck.

 

[lancekilgore]

Thanks for all the help all, I now have a course of action which i did not have before. I also have follow up actions to look into to ensure things are taken care of.

couldn't have done it with out your imput.

Lance

 

[ovittasbargu]

two way,
first one is RipRap. its cheap but you need to good foreman. he must be like puzzle as you know RipRap like an Puzzle and should be focus on key stone and unsoluble rocks.

another one is Gabion desk. its not cheap.