WEBVTT Kind: captions Language: en 00:00:05.950 --> 00:00:08.029 Brandon Forbes: The minute 319 pulse flow experiment flood 00:00:08.029 --> 00:00:13.500 in the Lower Colorado River Delta allows scientists to have the interesting opportunity to study 00:00:13.500 --> 00:00:22.680 many different aspects of a flood: from water quality, to recharge, rates and volumes, to 00:00:22.680 --> 00:00:24.410 the actual flood itself. 00:00:24.410 --> 00:00:31.189 And Jeff Cordova and I were able to install CSA or Continuous Slop Area sensors in a reach 00:00:31.189 --> 00:00:34.610 just downstream of the dam that was opened up where the flood was released. 00:00:34.610 --> 00:00:40.780 These sensors allow us to estimate what the discharges is and normally we put these gages 00:00:40.780 --> 00:00:46.930 or Continuous Slop Area sensors in areas that are impacted by wildfire or are just hard 00:00:46.930 --> 00:00:48.790 for our technicians to reach. 00:00:48.790 --> 00:00:53.989 So it's hard to actually hard to get to a spot and measure and a difficult thing to 00:00:53.989 --> 00:00:59.770 estimate when we do this kind of method is the roughness that the vegetation actually 00:00:59.770 --> 00:01:02.380 pushes against the water during the flow event. 00:01:02.380 --> 00:01:05.880 And you have to estimate this while you're in the field and this goes into the Manning's 00:01:05.880 --> 00:01:08.560 equation so we can estimate discharge. 00:01:08.560 --> 00:01:14.310 In this unique event in the pulse flow, in the Colorado River, we were able to put these 00:01:14.310 --> 00:01:18.920 sensors in and we knew when the flood was coming and how big it was going to be so we 00:01:18.920 --> 00:01:24.560 could prepare before the flood and collect as much data as possible during the event. 00:01:24.560 --> 00:01:29.689 We also had the ability for our scientists in the Yuma field office to make high quality 00:01:29.689 --> 00:01:36.580 and very highly accurate discharge measurements using ADCPs or Acoustic Doppler Current Profilers, 00:01:36.580 --> 00:01:41.719 and they did this at multiple times during the event which allowed us to have very accurate 00:01:41.719 --> 00:01:46.829 discharge measurements where we could compare this with the CSA or Continuous Slop Area 00:01:46.829 --> 00:01:50.049 sensors that we had deployed in the reach. 00:01:50.049 --> 00:01:55.380 This gives us the opportunity to actually back calculate the roughness value at the 00:01:55.380 --> 00:02:00.670 times that our technicians in Yuma measured discharge. 00:02:00.670 --> 00:02:05.229 During the installation of the CSA sensors, all the sensors in the reach were programmed 00:02:05.229 --> 00:02:10.099 to collect stage, or the depth of water, every five minutes throughout the duration of the 00:02:10.099 --> 00:02:11.120 flood event. 00:02:11.120 --> 00:02:14.860 Once the sensors were properly programmed to collect data at the correct intervals, 00:02:14.860 --> 00:02:18.069 which can be done in the field, the sensors were anchored in the channel to prevent them 00:02:18.069 --> 00:02:20.819 from moving during the flood event. 00:02:20.819 --> 00:02:25.709 Once the CSAs are fully installed, we mark each cross section associated with each sensor 00:02:25.709 --> 00:02:31.519 in the CSA reach so that a survey can be conducted to record the shape of the channel and the 00:02:31.519 --> 00:02:36.170 height of the sensor at each cross section. 00:02:36.170 --> 00:02:41.360 Here we are surveying the channel geometry at each cross section using a Total Station. 00:02:41.360 --> 00:02:45.390 This is an accurate tool used to measure the height of each sensor as well as the shape 00:02:45.390 --> 00:02:49.040 of the channel at each cross section in the CSA reach. 00:02:49.040 --> 00:02:54.450 The Prism at the top of the survey rod is used as a target for the Total Station; when 00:02:54.450 --> 00:02:58.580 using this equipment, there needs to be line of sight between to the Total Station and 00:02:58.580 --> 00:03:04.070 the Prism, this is not always possible give the winding nature of rivers and the vegetation 00:03:04.070 --> 00:03:05.530 you can see here. 00:03:05.530 --> 00:03:09.030 In such cases, a reference mark is used. 00:03:09.030 --> 00:03:14.269 Here it is a stake hammered into the riverbed and is used as the reference mark. 00:03:14.269 --> 00:03:19.040 The mark can be seen multiple cross sections when the Total Station is moved. 00:03:19.040 --> 00:03:22.969 This ensures that the survey between the two points where the Total Station has been set 00:03:22.969 --> 00:03:24.750 up remains on the same plane. 00:03:24.750 --> 00:03:30.709 Yeah this is going to be CSGX4; the pin will be four. 00:03:30.709 --> 00:03:37.499 Yeah I'll do the top of the T post then I'll try and get the sensor level. 00:03:37.499 --> 00:03:38.560 Ready. 00:03:38.560 --> 00:03:44.010 This is Brandon Forbes, April 25th. 00:03:44.010 --> 00:03:51.849 But I'm going up to our upper most sensor in the slope area reach; the water's about 00:03:51.849 --> 00:03:52.980 six feet deep here. 00:03:52.980 --> 00:03:58.510 The channel changed quite a bit, but it's way deeper than it was when we first installed 00:03:58.510 --> 00:03:59.510 the sensors. 00:03:59.510 --> 00:04:00.510 Yes! 00:04:00.510 --> 00:04:01.659 And there she blows. 00:04:01.659 --> 00:04:10.220 She looks good, stable; it's in this clay layer right here. 00:04:10.220 --> 00:04:12.680 Very very nice. 00:04:12.680 --> 00:04:18.639 Now that the flood is over and the dam is now shut off, we have conducted three surveys 00:04:18.639 --> 00:04:23.610 of the channel bottom and the heights of the four sensors that we deployed in the reach, 00:04:23.610 --> 00:04:29.480 and we've also measured the water with ADCPs multiple times during the event. 00:04:29.480 --> 00:04:35.960 Now we're looking at all the data and we're going to compare the two and see what we get. 00:04:35.960 --> 00:04:40.240 It's very important to survey after the flood, because a lot of times the channel can change, 00:04:40.240 --> 00:04:44.440 and what we're seeing already in that the channel is filled with fine sediment that 00:04:44.440 --> 00:04:48.630 was carried from the dam and down into the reach where we measured. 00:04:48.630 --> 00:04:52.760 And this can affect the cross-sectional area of our estimate, so it's very important to 00:04:52.760 --> 00:04:58.250 capture this now right after the event occurred so we can have the closest estimate of what 00:04:58.250 --> 00:05:05.340 the channel looked like while the event was happening. 00:05:05.340 --> 00:05:10.170 This is an efficient tool to measure the channel profile and the channel characteristics that 00:05:10.170 --> 00:05:12.250 we use in a lot of streams in Arizona. 00:05:12.250 --> 00:05:19.750 It's called an RTKGPS and this is a high accurate survey grade GPS unit that we can take out 00:05:19.750 --> 00:05:23.470 into the field and measure channel properties without line of sight. 00:05:23.470 --> 00:05:28.730 With traditional survey equipment like the Total Station, you need line of sight and 00:05:28.730 --> 00:05:32.670 it's far more difficult to get through the canopy and through the vegetation that we 00:05:32.670 --> 00:05:35.220 have on the banks of the streams. 00:05:35.220 --> 00:05:41.210 The RKTGPS allows us to go to any point where we can get a GPS signal, and that we want 00:05:41.210 --> 00:05:45.890 to know the exact XYZ coordinates of that point. 00:05:45.890 --> 00:05:50.650 In Arizona it's vet difficult to get to a flood while it's occurring because floods 00:05:50.650 --> 00:05:51.910 happen so fast. 00:05:51.910 --> 00:05:56.970 In this unique opportunity we knew the flood was going to happen which gave us an incredible 00:05:56.970 --> 00:06:02.550 heads up on we could collect during the event and now process after the event has occurred 00:06:02.550 --> 00:06:05.770 to try to learn as much as we can from the pulse flow event. 00:06:05.770 --> 00:06:09.880 Now we are compiling, collecting, and analyzing all the data we collected during the flood 00:06:09.880 --> 00:06:14.160 event and we hope to have interesting results we can share in the very near future.