River flow calculations for gabions
River flow calculations for gabions
(OP)
I am working with the native population in Panajachel, Guatemala. I am trying to design a river containment system (dikes) with 30º bank slope, covered with 9" x 2m x 4m gabions o/geotec fabric. The river gradient is 200'/mile, the width 70m, x 2m max depth (20,775 cfs)for max (1) 12hr period once a year. Normal flow is 1-4000 cfs or less. River velocity at full capacity is 21.2fps. Can I use gabion mattresses at that flow?, and if they fail, how would they fail?. Can occasional deadmen be attached to resist movement.?





RE: River flow calculations for gabions
Gabions fail in different ways. High velocity flow can lift a section of mattress and move it. Debris can snag a wire and break it and then the riprap gets carried away by the current. Alternatively, one or two missing hog rings or a missing tie wire can cause the same thing. Holes or gaps in the filter fabric can allow soil to be piped out during high flow, creating a void below the gabions. High velocity flows can also just deform the baskets leaving a very rough surface. Scour at the toe of the slope can create a hole and the mattress slides in.
RE: River flow calculations for gabions
RE: River flow calculations for gabions
RE: River flow calculations for gabions
RE: River flow calculations for gabions
RE: River flow calculations for gabions
RE: River flow calculations for gabions
RE: River flow calculations for gabions
RE: River flow calculations for gabions
RE: River flow calculations for gabions
RE: River flow calculations for gabions
thanks for the help...
The river shown in the attached section is depicted at maximum expected 1000yr flood stage (4" rain/hr.), dashed line at Agatha level (1.7"/hr). The typical river level meanders in the river basin at 200cfs in the dry season to 1-4000 cfs between storms in the rainy season. At max expected flood, we are calculating 52,972 cfs. The main culprit is a slope of 200+'/mile. I have not seen HECRAS in operation before, but I reviewed the program online and it seems dooable. I will download the program and see what I can do with it... not sure it I am experienced enough to run it but I will see. the first posting I sent has the calcs for flow.
RE: River flow calculations for gabions
I really quickly calc'd the shear stress at the toe of slope at: normal (Agatha) stage which is +/-10lbs/ft2 and at max stage which is +/-18 lbs/ft2. With this information you may want to investigate other types of protection. I really don't think the reno's will do the trick. Have you called MacCaferri directly and chatted with them?
RE: River flow calculations for gabions
there has not been any other study done, than by map analysis, transit for gradient, and visual observations and calculations for water flow.
I have contacted MacCaferri. They are looking into it now.
RE: River flow calculations for gabions