Pond Boss Forums MANAGING AN EXISTING POND Evaluating and adjusting fish populations Managing Sediment flow into Pond

Hello - I have a 2.5 acre pond that sits at the bottom of a valley. It is spring fed and typically stays around the same level, unless we have a very long summer drought. The main source of water bubbles up out of the ground about 1000 feet from the pond and trickles down a creek bed into the pond. There is another inlet that catches alot of run off, but a very high water table. In this area and in one spot near the main creekbed the water bubbles out of the ground just from driving a mower over it.

Where the main creek bed feeds into the pond, I get sand / sediment build up creating a sand bar. I just had the pond dregged and removed a lot of water shield and muck / built up sediment and quite a large sand bar. There is a link below tgat contains a video which should give you a pretty good idea of my issue. About 3 years ago watershield totally took over the pond. In the video when I pan out to show the pond, that used to be completely covered in watershield. The remaining watershield you see is where the excavator couldnt reach. The watershield was so thick that as the sediment rushed into the water it hit a wall of weeds and the sediment just built up there. I thought that dredging and removing the watershield would solve this issue. Last night we had our first massive rain since the pond was worked on and now the problem is back.

https://www.dropbox.com/scl/fi/d3q3...771txuvc86opvyy&st=3pf4rb0a&dl=0

When we get these heavy rains the water just RUSHES down the creekbed (normally it is a trickle). This time I could see alot of the sediment disperse into the water, but it still made this sandbar. How can I prevent this sand bar from forming? I just built a land bridge over the creek and I'm going to add a bunch of rip rap near the pipe inlet and outlet, and a few other places above and below the pipe to prevent washout and also slow the water. Will the rip rap help by slowing the water down? Would love to know if anyone else has had this issue of sediment build up and how to prevent it.

I should also note that I have a pond siphon overflow which i've been having trouble with. I've attached a picture for reference (but not sure it will work so here's a video https://www.dropbox.com/scl/fi/ytc5...4av69wabzskita8&st=xi71tav2&dl=0 ) . In the picture the highlighted circle shows what I will refer to a water level control pipe. My pipe is 2 inches in diameter and originally extended about 3 feet under water at about a 45 degree angle. It has several holes drilled into it. The siphon is supposed to break once the water level hits one of these holes. It doesn't stop on mine until the water gets all the way to the end of water level control pipe. Incredibly frustrating as we'll get heavy rains at night, and then I wake up and my pond is drained. I drilled a bunch more holes into the pipe; it didn't break siphon. I cut the end of the pipe off so that the water level wouldn't get so low, and then drilled even more holes. It didn't work, but now it stops pumping at a level i can live with. Perhaps this fix is for another thread, but i thought i should mention this because in my mind, if the water is pumped out faster than its coming in, then at some point the sedimentary water will start to build up at the inlet because the water has become shallow there and it doesn't have as much depth to disperse. Is my logic sound?

If there is room on the property, dig a sediment pond before the main pond where the creek flows into the main pond. The water velocity will slow down, the sediment will drop out there and enter the main pond. Plan on cleaning out the sediment pond annually. That's really the only fix to the problem.

esshup has described above the optimal solution. If you want more information, research a "sediment pond" or a "settling pond".

I would design it such that I could easily get an excavator (or mini-excavator as pond size requires) to the location at an effective angle to periodically clear out the accumulated sediment and pivot to dump it in a place that is acceptable or easily spread.

IF you are going to build a small pond on your property, you could also consider making it a "dual use" pond. Make it a forage pond, brooder pond, etc. If you are going to spend money/time building improvements that help your large pond, might as well get a bigger bang for your buck.

There is also a more subtle physics concept at play. The amount of elevation change from the top of a stream to its local "base level" has a huge effect on the erosive power of water moving through that stream. In the steep landforms of the American West, you can easily observe the ravines that are sharply cutting into the rock cliffs. Any loose material is immediately transported down with the running water because it is well above the local base level. However, as soon as the flowing water hits the floor of the valley it immediately drops 99% of its sediment load. That is because the local base level of the valley 10 miles downstream may only be a foot lower in elevation than the base of the cliff. These deposits at the toe of the cliff are called alluvial fans.

Sorry for the long lesson, but it was necessary to explain another solution to you. Any time you can create a higher local "base level" in your stream, you will reduce the erosive power of the stream. If you have some easy spots in the seasonal stream, you could install some chuck dams. These could be almost anything based on your available materials and how you want to effect the visual appeal of the stream (if that matters). You could fell a big tree and drop the trunk across the stream, you could use rocks from your property, or free concrete demolition debris, etc. You just need to make a dam that creates a temporary pool during a heavy rain event. Your dam is probably better to be imperfect. If a bit of water runs through your rock pile dam, but it still creates a pool, then you will have reduced the erosive capacity of your stream (and the amount of sediment transported to your settling pond), yet your chuck dam will be less likely to be over-topped - which might cause erosion of the banks of your stream.

Finally, can you improve the groundcover density on your land before that surface runoff accumulates into your creek? For example, dense forest sometimes has sporadic ground vegetation. If you are cutting trees for firewood, etc., then make some deliberate clearings to enhance the growth of rooted ground vegetation for erosion control. Narrow clearings perpendicular to the slope running down the the stream would be your most efficient means of trapping sediment before it even reaches your stream.

Good luck on your improvement projects for your large pond!

Not only make the settlement pond easy to dig out with an excavator, make it easy to get a dump truck there to put the spoils into it as you bucket it out of the settlement pond. Touch it once if possible.