Feeds:
Posts
Comments

Archive for December, 2011

The State of Vermont issued its first hydraulic geometry report in 2001 and then did a follow-up report in 2006 with a focus on smaller streams. For both reports, I took a look at the data and tried to add a bit more analysis (2001 review and 2006 review) and I offered some critiques to the reports.
One aspect that surprised me upon closer inspection of the USGS measurement data were how few overbank measurements were made. The USGS has a very well established protocol on stream measurements and rating curve development. All of that is great, but at some point, even the best made curves do start to become and extrapolation at higher flows. While I can fully appreciate staffing and resource limitations, as well as very legitimate safety concerns, it did surprise me that in some cases, several feet of stage change were essentially an educated and professional judgement guess for the associated discharge during high flow runoff events.

With respect to hydraulic geometry curves, this link is one I check perhaps 3 or 4 times a year to see if there are any updates, particularly for my area of interest in New England.

Advertisements

Read Full Post »

The USGS has put out a nice report looking at some of the impacts that occur to rivers within a watershed such as diversions and changes in percent impervious cover.  The report is quite detailed and goes into some fairly complex statistical routines (principal component analyses and generalized linear models).  Fortunately, the take home message is fairly clear.  As more and more water is diverted from a system in August due to groundwater withdrawals, the relative abundance of fluvial fish goes down.  The other key finding is that increases in impervious cover within a watershed also decreases the abundance of fluvial fish overall and appears to have the greatest affect at decreasing the abundance of brook trout relative abundance.

The report can be obtained from here.

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 »

This article goes a bit deeper in depth about some of the implications of shutting down so many gauges.
http://stateline.org/live/details/story?contentId=620251

Read Full Post »

I understand that with a federal deficit in excess of a trillion dollars, cuts need to be made. Nevertheless, it is unfortunate to read that the USGS is proposing to stop operating 580 gages.

http://www.steubencourier.com/mobiletopstories/x669904219/Schumer-to-USGS-Keep-N-Y-river-gauges-running

I’ve always thought that floods and drought could not care less about one’s politics, people with left, right and centrist politics are all affected.  In addition, the data these gauges generate benefit all Americans.  The ability to predict floods and manage water resources will be significantly diminished if these gauges are discontinued.

Read Full Post »

Bummer

I happen to live relatively close to the Larkin Road dam on the Parker River in Newbury, MA.  I also happen to know some of the NOAA NMFS staff that have been involved with the project.  A nice feasibility study was completed by Gomez and Sullivan and some pre-removal baseline data collection has already occurred.  The dam is old and essentially serves no function (no hydropower, no flood control, no water supply) so it seems as though it is a good candidate for removal. Apparently the Newbury Board of Selectmen felt otherwise:

Selectmen Say No To Dam Removal

Maybe the dam will come out someday, but this vote sets the whole project back quite a ways.

Read Full Post »

%d bloggers like this: