WEBVTT 1 00:00:05.860 --> 00:00:07.180 Hi, this is Chris Morris 2 00:00:07.180 --> 00:00:08.490 and I'm the surface water specialist 3 00:00:08.490 --> 00:00:10.770 at the USGS in Las Vegas, Nevada. 4 00:00:10.770 --> 00:00:13.400 I will be talking about non-standard culverts. 5 00:00:13.400 --> 00:00:15.060 In previous videos I discussed surveying 6 00:00:15.060 --> 00:00:16.100 the approach high-water marks, 7 00:00:16.100 --> 00:00:18.817 the tailwater high-water marks, an approach cross-section, 8 00:00:18.817 --> 00:00:21.110 and the general attributes of box, pipe, 9 00:00:21.110 --> 00:00:23.060 and pipe arch culverts. 10 00:00:23.060 --> 00:00:25.650 Even if you have some aspect of a non-standard culvert, 11 00:00:25.650 --> 00:00:27.080 you will still need to measure features 12 00:00:27.080 --> 00:00:28.653 described in those videos. 13 00:00:29.690 --> 00:00:31.660 The information presented in this single-component video 14 00:00:31.660 --> 00:00:35.140 can also be found in TWRI 3-A3, 15 00:00:35.140 --> 00:00:36.690 Measurement of Peak Discharge at Culverts 16 00:00:36.690 --> 00:00:38.290 by Indirect Methods. 17 00:00:38.290 --> 00:00:39.790 Not every unique circumstance 18 00:00:39.790 --> 00:00:41.290 can be discussed in this video, 19 00:00:41.290 --> 00:00:42.740 so if you do have a non-standard culvert, 20 00:00:42.740 --> 00:00:44.550 having the TWRI to reference in the field 21 00:00:44.550 --> 00:00:45.973 is especially important. 22 00:00:47.150 --> 00:00:48.890 As mentioned in previous videos, 23 00:00:48.890 --> 00:00:50.510 good clear notes are needed. 24 00:00:50.510 --> 00:00:52.830 With complex culverts or when combined with other methods, 25 00:00:52.830 --> 00:00:54.900 say a road overflow, it is easy 26 00:00:54.900 --> 00:00:56.530 to forget to measure the beveling or note 27 00:00:56.530 --> 00:00:58.780 if you measured the top or bottom of the culverts. 28 00:00:58.780 --> 00:00:59.970 There is nothing worse than finding 29 00:00:59.970 --> 00:01:02.420 that a critical element was missed a few months ago, 30 00:01:02.420 --> 00:01:04.430 and an additional site visit or survey is needed 31 00:01:04.430 --> 00:01:06.340 to finish the computation. 32 00:01:06.340 --> 00:01:08.190 Even for someone who has surveyed many culverts, 33 00:01:08.190 --> 00:01:09.610 I find having a checklist is useful 34 00:01:09.610 --> 00:01:10.960 to get everything you need. 35 00:01:12.010 --> 00:01:13.750 Let's first look at mitered culverts, 36 00:01:13.750 --> 00:01:15.170 or those with entrances and exits 37 00:01:15.170 --> 00:01:18.020 that are at an angle to match the embankment. 38 00:01:18.020 --> 00:01:20.270 The top and bottom of the culvert have different lengths, 39 00:01:20.270 --> 00:01:23.060 so where should you measure for the total culvert length? 40 00:01:23.060 --> 00:01:24.700 If the culvert entrance was submerged, 41 00:01:24.700 --> 00:01:26.790 completely underwater, the length of the culvert 42 00:01:26.790 --> 00:01:27.970 from the top of the entrance 43 00:01:27.970 --> 00:01:30.500 to the top of the exit should be measured. 44 00:01:30.500 --> 00:01:32.510 If the culvert entrance was not submerged, 45 00:01:32.510 --> 00:01:34.540 the length of the culvert from where the water surface 46 00:01:34.540 --> 00:01:36.710 first intersects with the culvert entrance 47 00:01:36.710 --> 00:01:38.350 and where it intersects with the culvert exit 48 00:01:38.350 --> 00:01:39.403 should be measured. 49 00:01:40.840 --> 00:01:42.730 The question of the length from the culvert 50 00:01:42.730 --> 00:01:44.520 for the approach also arises. 51 00:01:44.520 --> 00:01:46.400 Should you measure from the top of the culvert entrance 52 00:01:46.400 --> 00:01:47.540 or the bottom? 53 00:01:47.540 --> 00:01:49.090 This one requires a little math. 54 00:01:49.090 --> 00:01:51.140 Don't worry, it's easy. 55 00:01:51.140 --> 00:01:53.350 Take the water surface elevation at the approach 56 00:01:53.350 --> 00:01:55.650 and subtract the elevation at the invert, 57 00:01:55.650 --> 00:01:57.660 or the bottom of the culvert entrance. 58 00:01:57.660 --> 00:02:00.370 Now divide this number by the culvert diameter. 59 00:02:00.370 --> 00:02:01.940 If the result is less than one, 60 00:02:01.940 --> 00:02:04.980 then measure the distance using a tape from the approach 61 00:02:04.980 --> 00:02:06.830 to where the water surface first intersects 62 00:02:06.830 --> 00:02:08.730 with the culvert entrance. 63 00:02:08.730 --> 00:02:11.020 If the number calculated is greater than one, 64 00:02:11.020 --> 00:02:12.470 then measure the distance using a tape 65 00:02:12.470 --> 00:02:15.050 from the approach to the top of the culvert. 66 00:02:15.050 --> 00:02:17.340 Finally, sometimes the first length of a mitered culvert 67 00:02:17.340 --> 00:02:19.710 is at a different slope then the rest of the pipe. 68 00:02:19.710 --> 00:02:22.650 If so, measure the culvert invert at full pipe, 69 00:02:22.650 --> 00:02:25.260 or when the mitering of the pipe stops. 70 00:02:25.260 --> 00:02:26.830 If there are multiple culverts, 71 00:02:26.830 --> 00:02:28.870 the distance for the approach upstream should be 72 00:02:28.870 --> 00:02:32.730 at least one to three times the sum of the culvert widths. 73 00:02:32.730 --> 00:02:34.840 Sometime the culverts may have different slopes, 74 00:02:34.840 --> 00:02:36.190 be made of different materials, 75 00:02:36.190 --> 00:02:38.030 or have different elevations. 76 00:02:38.030 --> 00:02:40.780 All culverts need to be surveyed and measured. 77 00:02:40.780 --> 00:02:42.880 Additionally, the separation between each culvert 78 00:02:42.880 --> 00:02:44.880 should be measured and noted. 79 00:02:44.880 --> 00:02:47.590 line:15% For those that are located more than 10% of the diameter 80 00:02:47.590 --> 00:02:49.340 or width of the culverts apart, 81 00:02:49.340 --> 00:02:51.150 they will be treated as multiple components, 82 00:02:51.150 --> 00:02:53.140 as is discussed in another video, however, 83 00:02:53.140 --> 00:02:55.950 no additional field work will be needed. 84 00:02:55.950 --> 00:02:57.970 After a flood, material is often found 85 00:02:57.970 --> 00:02:59.143 in the culvert itself. 86 00:03:00.540 --> 00:03:03.000 More often than not, here in Nevada I find sand fill 87 00:03:03.000 --> 00:03:05.320 in the first few feet of the culvert. 88 00:03:05.320 --> 00:03:06.760 When this material is loose, 89 00:03:06.760 --> 00:03:09.220 it is typically assumed that at the peak itself, 90 00:03:09.220 --> 00:03:11.290 the high velocities keep the culvert clean 91 00:03:11.290 --> 00:03:12.510 and the material is deposited 92 00:03:12.510 --> 00:03:14.560 on the recession of the peak. 93 00:03:14.560 --> 00:03:17.710 The next peak again removes it on the rise. 94 00:03:17.710 --> 00:03:19.960 However, at some sites the material is well compacted 95 00:03:19.960 --> 00:03:22.170 or naturally cemented and doesn't appear to change 96 00:03:22.170 --> 00:03:24.180 as a result of peaks. 97 00:03:24.180 --> 00:03:26.980 The same can be true for debris at the entrance. 98 00:03:26.980 --> 00:03:29.220 If it is thought the material was present at the peak, 99 00:03:29.220 --> 00:03:31.290 the obstructed area needs to be measured. 100 00:03:31.290 --> 00:03:33.530 For example, if I found gravel well compacted 101 00:03:33.530 --> 00:03:34.940 and cemented in a box culvert, 102 00:03:34.940 --> 00:03:37.640 I would need survey a cross-section in the culvert, 103 00:03:37.640 --> 00:03:39.000 or if that was not possible, 104 00:03:39.000 --> 00:03:41.170 dig part of the culvert clear and use a folding ruler 105 00:03:41.170 --> 00:03:45.320 to directly measure the depth to compute an accurate area. 106 00:03:45.320 --> 00:03:47.810 Take time in the field to assess if the culvert was clear 107 00:03:47.810 --> 00:03:50.453 at the peak or was impacted by debris or fill. 108 00:03:51.410 --> 00:03:53.580 Some culverts actually have natural bottoms. 109 00:03:53.580 --> 00:03:56.140 In such situations, a cross-section needs to be surveyed 110 00:03:56.140 --> 00:03:58.450 at both the culvert entrance and exit. 111 00:03:58.450 --> 00:04:01.770 An average elevation will be used for the invert. 112 00:04:01.770 --> 00:04:04.500 A final special case is running a slope-area measurement 113 00:04:04.500 --> 00:04:06.310 inside of a culvert. 114 00:04:06.310 --> 00:04:07.750 Unlike a natural channel, 115 00:04:07.750 --> 00:04:09.470 a culvert with a concrete or metal floor 116 00:04:09.470 --> 00:04:11.890 is not subject to scour or fill. 117 00:04:11.890 --> 00:04:14.210 In the situation when the flow was not conducive 118 00:04:14.210 --> 00:04:17.780 to a culvert measurement, this can be a good alternative. 119 00:04:17.780 --> 00:04:19.800 However, often high-water marks are hard to find 120 00:04:19.800 --> 00:04:22.100 inside the culvert barrel and flow may be wavy 121 00:04:22.100 --> 00:04:25.510 or indicative of unsteady flow from high velocities. 122 00:04:25.510 --> 00:04:27.720 If a slope-area measurement is attempted, 123 00:04:27.720 --> 00:04:29.910 it should be done away from the culvert entrance. 124 00:04:29.910 --> 00:04:31.560 More information about slope area measurements 125 00:04:31.560 --> 00:04:33.790 line:15% can be found in other videos. 126 00:04:33.790 --> 00:04:34.840 If you need help in the field, 127 00:04:34.840 --> 00:04:36.710 call your supervisor, surface-water specialist, 128 00:04:36.710 --> 00:04:38.460 or indirect measurement specialist.