text: need help in building a small dam (about half a foot in height) to prevent erosion of soil? in the place where i live, during rains the ground besides me becomes a small stream. what that does is that it erodes the soil and the place becomes very uneven after monsoon. so every year we have to bring truckload of soil to fill the small gorges. so this time i built a small mud dam but then during heavy rainfall the water flows over it and takes the soil with it. so what should i do so that the soil does not get eroded or water doesn't flow? and for ur information the place has a slope of about 10-15 degrees several courses of action should be taken.  if there is no alternative to the slope, then you should force the water to go a longer distance, and make the slope smaller, like a down hill skier.  reducing the slope and putting in many bends will slow the water down more.    upstream, a retention pond should be put in, or a sizable pool that will fill with water, slow down the water, and really delay the water form heading downstream all at once.  although if you have monsoons, this may not have maximum effect.  during the dry season, plant in the streambed and beside it where the water goes.  try to use plants that are typically in or near the water or the stream.  this will slow the water down, and the roots will help hold onto soil to keep it from washing away.  after these options, a small dam could be put in.  start by placing wooden or metal poles in a line, slightly bowed out going upstream, across the stream bed.  from there, place wooden or metal poles laid down across the perpendicular poles.  then place the soil on top of that.  in the middle of the dam, you will want it open in a v shape going up the dam, to allow water to still pass through.  a v shape will allow the little bit of water to pass when it is dryer, but more to pass when it is wetter.  ideally you should put a layer of concrete over the dam to stop it from eroding, but if not, then just pack it very tightly and put more plants right into the dam.  though some of this sounds expensive and time consuming, will save in the end if you dont have to truck in the sand.    if its part of a road, use cement/ brick/ mudbricks over the section that water flows on.  if its a short section, see if it would be possible to install a culvert (pipe) so that water will flow under and not over the road.  without additional information, i can only suggest rocks and boulders in the area to slow the water and prevent erosion.  other techniques that you can research that are more specific to your situation may be found on a yahoo search, or if you have some money, invite an engineer (geotechnical or civil) to the site if possible.