Intro slide. Names: As Kayce said, my name is Anthony Alvarado, I am a PE and a project manager of our geomatics engineering group at Ayres Associates. I have been a part of hydrosurvey work for over 7 years and involved with GIS for over 8 years. With me today is Dusty Robinson, also a PE working for Ayres Associates with nearly 10 yrs of hydrographic survey experience. Thank you for coming and I hope that is interesting and educational for you. If you have questions, please feel free to interrupt me, don’t feel like you have to wait til the end. Now with that, why a discussion of hydrographic survey at GIS in the Rockies? In the middle of landlocked Colorado?
Reason why hydro survey on rivers is important. Bridge failure is bad. I think these bridges were in NY. Caused by bridge scour. Can’t simply inspect bridges, need accurate data to model scour on a new or existing bridge. Of course, there are plenty of bridges in Colorado…
Levees. This picture should be near the delta of the Sacramento River, just a weak spot in the levee that eventually failed when flow came up. Hydro survey on rivers is important. Levees need a lot of work in the Sacramento Area as well as plenty of other areas in this country protect by levees including even Pueblo, CO and of course the area that most comes to mind, New Orleans. Hydrosurvey is a part of levee and bank protection design and the system wide hydraulic modeling that allows for adequate levees.
Another area that hydro survey plays into... One that hits a little closer to home here in Colorado… floods. Hydrosurvey comes into play in the need for accurate bathymetry for accurate hydraulic modeling…
Other major uses of hydrographic data: reservoir sedimentation, habitat analysis and monitoring. In the mid 90s, we were and are doing all of this from hydraulic modeling, bridge scour analysis, and flood mapping to stream restoration, levee repair and habitat analysis, we needed this data so we simply developed the capability to do this in-house. But with all this, if I were to ask what comes to your mind when I say “hydrosurvey”, this might come to mind…
Typically when most people think about hydrographic survey, if they have any concept of it, they might think of this… an ocean or coastal survey. Or…
Or we might think this when thinking hydrosurvey or how to obtain bathymetry… Just wade the section!
Today, the world I want to talk briefly about is the world in between… about hydrographic survey in shallow water streams and how it’s done and the equipment involved and then a few project examples. Not so typical hydro survey perception: The big boats with outboard props. These boats are typically used on larger channels and reservoirs. The top picture was taken at Fort Peck Lake, Montana while the lower picture was taken on Sacramento River near Sacramento during a high flow event. One key thing to understand is that you need the right equipment for the right job. Seems pretty obvious but it’s significant when it comes to hydrographic surveying on shallow inland water bodies.
Again, a not so typical hydro survey perception: The standard boats with outboard jets. The jet boat is our most prominently used hydrosurvey craft. The upper picture is on the American River while the lower photo is on the Sacramento River
And the extremely untypical hydro survey vehicles: The specialized boats. The airboat on the Platte River in Nebraska, the zodiac in a small pond, the cataraft on the Rio Grande near Bernalillo, NM.
I’d like to now take you through an example of the full hydrosurvey process on a river where 2ft contour mapping is desired. In this case, this is the San Joaquin River, just south of Stockton, California which is south of Sacramento. The project in this case was to survey near 300 miles of channel in San Joaquin system back in 1997. I’m going to show you a part of that and I’ll show you a typical set-up now not necessarily what was used back in 1997.
Pictures of the San Joaquin River including a bird’s eye view out of Bing.
So here is the typical setup with the typical pieces: your positional equipment (note I do not limit this to simply GPS), the laptop or simply something that can integrate the position and depth data, the depth sounder, and the transducer. In my slide, you’ll notice we’re using a Leica 1200 GPS system , a Getac rugged laptop and an Innerspace 455 single beam survey grade depth sounder with an Airmar transducer. But again, think of these as examples of components. I’ll show an alternative to GPS in one of my project examples and I’ll dig into the depth sounders next along with the software on the laptop.
Depth Sounders. The key with depth sounders is to remember that every depth sounder or fathometer is coupled with specific type of transducer. So on the left are some typical fish finders (the upper one is on the high end) while on the right are some survey grade depth sounders. You could not take a transducer pictured with the Innerspace 455 and try to use it with a fish finder. That might be an obvious example but that starts to come into play even between the different survey grade depth sounder and dealing with single frequency versus dual frequency. Other differences, really? Besides about $5-10k in cost? For a design level bathymetric survey, the survey grade depth sounder is the way to go. But according to USACE standards on a typical hydrographic survey where a continuous DTM is being produced or just simple cross sections, the fish finders will actually do the job. The key is how accurate your GPS and how you actually process the data.
The big push now is multibeam depth sounders. Multibeam is to Singlebeam in way how High Density Laser Scanning is to GPS. The upgrade in detail is obvious. This photo is actually from the upper Sacramento River near Redding, California. The equipment shown is a Reson multibeam system.
There are major differences between Multibeam and Single Beam. The cost of multibeam is still significantly higher than single beam – we’re talking $10k versus $200k. Multibeam also is not built yet to work in shallower riverine areas. Part of this is how multibeam needs pitch and roll sensors and calibration for wherever you’re surveying. And, of course, multibeam is a lot more data. But multibeam should typically be less processing and less time in the field where it fits.
Software. The industry standard is HYPACK. HYPACK is still geared towards ocean and coastal hydrography but it does the job for riverine applications and it’s fantastic for reservoirs. In this example, the user is using set cross sections placed ahead of time in which they are using Hypack to track to, shown at the bottom left. Every other software package that we know of is associated with a specific depth sounder. Initially, when we got into this business, we developed our own in-house software package.
Now back to the survey process. Here you see our raw survey data straight from the field. Again, this was for 2ft contour mapping of the channel, not for design but for a continuous DTM of the channel. Notice the perpendicular cross sections. This is very important in accurately representing the hydraulic characteristics of the channel! Zig zags will not adequately represent the channel. Also, you don’t just have one more step after this. You cannot simply triangulate this data or you end up with a mess. Your triangles won’t be good and the curvature in the river will not be accounted for.
Here is the data edited and thinned. You still can’t triangulate this data or it misrepresents the curvature of the river, especially along the thalweg or centerline.
Now we see it processed to 50 ft sections and accounting for the bends in the river, using the perpendicular edited and thinned cross section data and interpolating 50 feet sections in between and along the curvature.
Combined with photogrammetry/LiDAR for complete topographic coverage. In this case, the photogrammetry work was done by our Madison office so it was a bit easier to work more closely with them to make sure we had good overlap.
Final surface with color coded contours
As with the rest of topographic survey, the big picture is pushing towards large data collection via remote sensing. With hydrographic survey, there is the emergence of Bathymetric LiDAR. I want to explain this a bit because it is slowly improving and there a lot of questions about it’s use. The basics is that it uses 2 light waves, with one return for the surface of the water, one return for the ocean bottom. The issue to remember with this is that it only works with clear water and even then only to a limited depth (roughly 50m). Biggest and most prominent use right now is along coastal areas, along the shoreline, for instance to track beach erosion. This technology has been tested also on the Rio Grande, a sand bed channel in New Mexicao and the Yakima River, on a higher mountain stream reach in Washington. There were mixed results. It worked well on the Yakima River but that was in a super clear mountain channel and they dropped the flow significantly to make it happen. Bathymetric LiDAR is growing but still does not work in a sediment laden channel like the Rio Grande or Mississipi.
Now I’d like to show 3 pretty unique examples a little different than the one I just walked you through. The first is this area near RM 208 on the Sacramento River near Chico, California. At the bottom of the picture you’ll see the diversion facility for an irrigation district known as the Glenn Colusa Irrigation District or GCID. GCID is the largest irrigation pumping station in Northern California where nearly 25% of our produce comes from. In the 70s, a bend in the river downstream (to the right) of here cut off which dropped the water surface elevation through here. This severely dampened their pumping ability due to having to account for salmon runs and meeting other needs. They thought about putting in a 3ft weir to raise water levels but that would have hindered both boaters and salmon. That led to our design of the gradient restoration facility – the white area barely seen…
This is essentially a rock ramp underwater with fish depressions. It meets needs of GCID, as well as allowing for functionality for boaters and fish.
Hydrosurvey was a huge part of this project in obtaining design conditions and then post-construction quality control and monitoring since then.
In this you see the number of points taken in this survey, where we are really trying to duplicate multibeam functionality without multibeam. This area would be tricky for multibeam though because it is relatively shallow, fast current and highly turbulent flow.
A few pics of the latest survey at GCID. Notice in the upper right photo, the change in flow. That change in flow occurs at the top of the structure where the rock begins.
Pueblo Dam outlet works for CH2M Hill in Pueblo. This dam is actually owned by the City of Colorado Springs and they were in the process of designing a new outlet structure. They needed to determine an accurate depth for the outlet area where the new structure will be built, as you can see the pilings in the rendering. But the area was difficult to access and yet design level accuracy (1ft contours) was needed. Too deep to wade and would take too long anyway.
Used the cataraft and a Leica robotic total station. Pete, seen operating the robotic total station, only dialed in the total station when it would lose lock. This survey also had a lot of safety issues so we had a dive specialist ready as well as a 4 th person on the bank not the total station operator. There was also a lock out procedure for shutting down the flow from the dam which also added pressure to this survey because our window of time was only a few hours.
Here we have the survey on the Platte River with Airboat and Jet Boat. This was and is for the Platte River Recovery Implementation Program who are basically looking at trying to restore historical crane and fish habitat. In this case we surveyed the profile along a 100-mile stretch of river along with selected cross sections for monitoring. We used one of our jet boats on part of the reach until we started to hurt the engine with the amount of sand it was sucking up! From there, we successfully set up our hydrosurvey equipment on the airboat and used it to hydrosurvey over 60 miles of channel, over 100 miles total. We’ve definitely had some unusual hydrographic survey recently. The economy and market situation has definitely hurt our workload in this area but these more unorthodox surveys keep popping up for us.