Feeds:
Posts
Comments

Archive for the ‘sediment budget’ Category

I just received this email and as a Utah State alum, I thought it was worth posting:

—————————————————————————————————

August 6-10, 2012
Intermountain Center for River Rehabilitation & Restoration
Utah State University
Logan, Utah

For more information and registration: http://cnr.usu.edu/icrrr/

This course is for those who wish to understand and apply the principles of sediment transport to alluvial channel assessment and design.  Principles of open channel flow and sediment transport are combined with watershed hydrologic and sediment source analysis to place channel assessment and design in the appropriate context. The course balances advance reading, lecture, field work, and hands-on exercises for estimating sediment supply, calculating sediment transport rates, forecasting channel response to water and sediment supply, and a class project incorporating gravel augmentation into channel design for dynamic fish habitat.  This course is intended for participants who are familiar with basic principles of river geomorphology.

Topics include:

  • Spatial analysis tools for estimating sediment supply at the watershed to reach level
  • Threshold and alluvial channel models, with guidelines for assessment and design incorporating uncertainty
  • Sediment transport calculations: challenges and methods, sediment rating curves, cumulative transport
  • Field measurement of sediment transport and guidance for different sampling approaches
  • 1-d flow and transport models: HEC-RAS applied to flow competence and sediment transport capacity
  • Forward and inverse application of mixed-size surface-based transport models

Principal Instructors

Peter Wilcock (course director), Professor, Geography and Environmental Engineering,
Johns Hopkins University

Tyler Allred, Principal, Allred Restoration

Patrick Belmont, Professor, Watershed Science, Utah State University

Susannah Erwin, Postdoctoral Associate, Watershed Science, Utah State University

Milada Majerova, Postdoctoral Associate, Watershed Science, Utah State University

The course is taught among the majestic peaks of the Wasatch and Bear River mountains near Logan UT. Cache Valley is a delightful place to visit in August.  Salt Lake City is easy to fly into and there are abundant opportunities for outdoor adventure before & after the course.

Read Full Post »

I haven’t written anything to date for this analysis.  I’ve simply manipulated data from the USGS Suspended Sediment Database and summarized them in a spreadsheet available from the Ohio DNR and made a map.  The watersheds that are delineated in the map were made using EPA Watershed Delineation add-on in HydroDesktop.  The one data point that jumps out at me is the 1982 annual load for the Salmon River: 1,158 tons/mi2/yr, 96% of which occurred on June 5th and 6th. (Granted, the record that year only had 245 days of data, and no data were collected on June 4th). In any event, the number is still quite large and puts it in league with some of the larger annual loads I saw while working in coastal northern California, an area known for its high sediment loads.  The subsequent question that makes me curious is how did the channel respond to this flood in early June, 1982?  I have to assume that the massive load of sediment was deposited somewhere, but I also have to assume that much of bed and banks were scoured. The Google Earth imagery goes back to 1990 and it suggests a fairly stable single thread channel that hasn’t migrated much in the past two decades.  The vast majority of the floodplain appears forested, so my assumption is that much of the suspended sediment was deposited on the floodplain on the receding limb of the storm event or it was simply carried downstream to the Connecticut River.

(Circling back to the Allen Brook analysis, these results from CT gauges make me question  all the more the estimated sediment loads using the SWAT model for subbasins 1, 3, 4 an d 22 which supposedly were generating annual loads in excess of 5,ooo tons per square mile.  As consulting colleague of mine in California once said to me, “Beware the uncalibrated model.”)

The other bit of insight I gleaned from these data are how episodic the pulses of suspended sediment are in New England.  Granted, the data are limited: only 3 gauges had 5 or more years of nearly complete (360+ days of data for a given water year).  Nevertheless, it still suggests to me that most rivers are relatively calm and not transporting an inordinate amount of suspended sediment and then WHAM!, a large and rare event occurs that has the ability to deliver a substantial amount of sediment, well outside the range of normal annual load variability (very roughly speaking 20 to 100 tons/mi2/yr).

I also used the Effective Discharge from Suspended Sediment spreadsheet available from the Ohio DNR here.  Unfortunately, I’ve never quite gotten the gist of the spreadsheet, despite looking at it and reviewing the hidden Calculation Table tab.  In any event, I’ve plugged in the data for the eight CT gauges.  The hyperlink in the first column should take you to the USGS data, and the hyperlink on the right should take you to the spreadsheet I’ve saved on Box.net.  Each spreadsheet is just under 6Mb and is saved in .xlsm format to save space and to allow the macros that Dan Mecklenburg at the Ohio DNR developed to be functional.

Station Number
(USGS Link)

Station Name
(Effective Discharge Spreadsheet Link)

1125415

Muddy Brook At Childs Hill Rd Nr Woodstock, CT

1127500

Yantic R At Yantic, CT

1184100

Stony Bk Nr West Suffield, CT

1184500

Scantic R At Broad Brook, CT

1192883

Coginchaug River At Middlefield, CT

1193500

Salmon R Nr East Hampton, CT

1199000

Housatonic R At Falls Village, CT

1200500

Housatonic R At Gaylordsville, CT

It is at this point that I’m seeking some help.  If anyone has some insight into how to reasonably estimate effective discharge for any of these gauges based on the available data, I would love for you to contact me.  Please feel free to use the comment section.

Read Full Post »

While searching for hydrologic and geomorphic data, I also ran across a study that occurred on the White River. The study contained some good data, particularly on Ayers Brook, and I wanted to try to take it a bit further and see if I could make a crude annual sediment load estimate. Admittedly, the calculations were assumption rich, but I’d like to think I was able to develop some reasonable estimates of annual sediment load. While consulting in California, it almost seemed as if sediment budgeting efforts were a dime a dozen, whereas in New England, they were very few and far between. Given my familiarity with various approaches to sediment budgeting efforts, I very much enjoyed doing the analysis. The one slight downside to the analysis is that the cross sections that were surveyed were not terribly wide which greatly hampered my analysis. Fortunately I was able to get my hands on one section that was large enough to handle larger flow. Without that one section, I would not have been able to make any estimate at all.

Ayers_Brook_numerical_sediment_modeling.pdf

While sediment budget efforts are not required or necessary for many stream restoration projects, I’ve always thought that they provide some valuable context for understanding a river system, how dynamic it is, how much the bed and banks aggrade and degrade.

For a really nice sediment budget effort done recently in New Hampshire, take a look at this paper done by my colleague Matt Collins.

Rates and processes of channel response to dam removal with a sand-filled impoundment

Read Full Post »

Back in 2004 I was living in California, but I knew I wanted to move to the east coast. Consequently, I started scouring the internet for various hydrologic and geomorphic datasets in New England. I ran across a TMDL for Allen Brook in Williston, VT that was listed as impaired for sediment. “Perfect!” I thought. I took the data from that report and tried to build upon the analysis a bit.

Now, back in 2004, the internet and aerial photography isn’t quite what it is today. At the time, Microsoft offered a service called Terra Server. As a user, I could one by one, download little black and white air photos. I then had to use a photo editor to stitch the photos together. The process was a bit tedious and time consuming.  Since this was merely a hobby for me, I limited the number of photos that I stitched together.

The take home message for me was that the SWAT model could produce some very high loads and in my opinion, loads that seemed unrealistic when converted into tons/mi2.  Parts of Northern California are known for its unconsolidated, highly erodible bedrock that is steep and subject to intense rain and earthquakes.  These factors are all missing in Williston, VT, yet some of the subbasins in the TMDL analysis were indicating loads in excess of 5,000 tons/mi2.

Allen Brook mainstem airphoto.ppt

While searching for geomorphic data, I also ran across the Ohio DNR website that was sharing it’s cross section template developed by Dan Mecklenburg.  The template was perfect fit for the data that were collected as part of the TMDL.  I plugged in all the data and developed the spreadsheet below.  The one step I never got around to was to develop a nice summary table of all the data produced in this spreadsheet.

Allen Brook cross sections.xls

Finally, while it really wasn’t much of an analysis, since Allen Brook has no gauge, I put in a bit of effort to find some nearby gages that could serve as a surrogate gauge.   Below is the brief write-up I did for that.

Allen Brook surrogate gauge analysis.doc

Read Full Post »

%d bloggers like this: