Posts Tagged ‘stony clove’

Bankfull Flows on Friday

Posted on: August 20th, 2018 by Tim Koch

On the evening of Fri­day, August 17th, 2018 some­thing very impor­tant hap­pened in the world of stream sci­ence and man­age­ment. The Eso­pus Creek, Birch Creek, and Wood­land Creek reached “bank­full discharge”.

Bank­full dis­charge is the amount of water flow­ing in the stream when the chan­nel is com­pletely filled to the brim, mea­sured in cubic feet per sec­ond (cfs). At bank­full, all the water is still con­tained within the chan­nel. Once bank­full has been exceeded, water spills out onto the flood­plain and the stream is tech­ni­cally flood­ing. The pho­to­graph below shows the Stony Clove Creek at near bank­full flow. The  unde­vel­oped flood­plain vis­i­ble on the left is acces­si­ble to the stream and ready to accept any flood waters in excess of bankfull.

(a)bkf2(b)Stony Clove headwater close to bankfull

(a) Stream cross sec­tion show­ing bank­full stage, (b). the head­wa­ters of Stony Clove Creek flow­ing at ~800 cfs, approach­ing bankfull

In the humid north­east, most streams will see a bank­full flow event every 1.5 years on aver­age. The last time we saw a bank­full flow in the Ashokan water­shed was Octo­ber 2017.

If any flow over bank­full means that the stream is flood­ing, then we can expect our rivers and streams to flood at least once every year and half. This is nat­ural, sta­ble stream behav­ior and high­lights the impor­tance of flood­plain management.

Bank­full dis­charge is crit­i­cal to stream man­agers because over time it is the flow that moves the largest amount of sed­i­ment, effec­tively shap­ing and main­tain­ing the chan­nel form. Due to the impor­tance of bank­full dis­charge for chan­nel main­te­nance, some of the research projects that we fund at AWSMP have trig­gers that are acti­vated fol­low­ing bank­full flow events.

Below is a chart that com­pares the stream flows observed on Fri­day the 17th (far right) to bank­full dis­charge. The Q1.5 col­umn is an esti­mated bank­full dis­charge based on sta­tis­tics. This is a use­ful esti­mate for bank­full when field derived val­ues are not avail­able. The most accu­rate way to deter­mine bank­full dis­charge is to read the stream. A well-trained eye can locate bank­full indi­ca­tors in the field such as depo­si­tional fea­tures or changes in bank slope, veg­e­ta­tion, and par­ti­cle size. By using these indi­ca­tors as a guide to mea­sure the dimen­sions of the stream chan­nel, highly accu­rate bank­full dis­charge val­ues can be cal­cu­lated (mid­dle column).

 

USGS Gage Station

Q1.5 (cfs) Cal­i­brated Qbkf (cfs)

Qmax 8/17/18 (cfs)

Eso­pus Creek at Allaben

2,524 2,772 2,950

Eso­pus Creek at Coldbrook

10,343

7,069

12,000

Birch Creek at Big Indian 287 331

588

Wood­land Creek above Phoenicia 1,650 -

1,720

 

Q1.5 = sta­tis­ti­cally cal­cu­lated flow that occurs roughly every 1.5 years, often used a sub­sti­tute for field-calibrated bank­full discharge

Cal­i­brated Qbkf = field cal­i­brated bank­full discharge

Qmax = instan­ta­neous peak flow mea­sure­ment from Fri­day, August 17th, 2018

 

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AWSMP Repairs Damage on Stony Clove Creek

Posted on: January 7th, 2016 by Brent Gotsch

The Ashokan Water­shed Stream Man­age­ment Pro­gram (AWSMP) has com­pleted a project to halt bank ero­sion on the Stony Clove Creek near Lanesville.  The chan­nel was restored through a 2,500-foot cor­ri­dor heav­ily dam­aged dur­ing Trop­i­cal Storm Irene. Restora­tion of the stream chan­nel cost approx­i­mately $1.5 million.

Dur­ing T.S. Irene, sev­eral homes were dam­aged by ero­sion and flood­ing, and sed­i­ment accu­mu­lated in the cen­ter of the chan­nel, push­ing stream flows toward the banks.

Stream banks con­tin­ued to retreat in front of three remain­ing homes and sev­eral large hill­slopes. The rapidly slump­ing hill­slopes con­tributed sig­nif­i­cant amounts of fine sed­i­ment to the stream. The sed­i­ments travel miles down­stream to the Eso­pus Creek and Ashokan Reservoir.

Engi­neers used a com­bi­na­tion of instream grade and flow con­trol struc­tures designed to mimic nat­u­rally occur­ring stream fea­tures to sta­bi­lize the chan­nel and erod­ing stream banks. The chan­nel was engi­neered to pass both low and high stream flows, and the sed­i­ment car­ried by those flows, with­out sig­nif­i­cantly eroding.

Kingston Equip­ment Rental, Inc. (Baker Broth­ers Exca­vat­ing) out of West Hur­ley built the project. The project was designed by con­sult­ing firm Milone & MacB­room, Inc. The Ulster County Soil and Water Con­ser­va­tion Dis­trict (SWCD) pro­vided over­all project management.

In 2016, the Ulster County SWCD will work with landown­ers at the project site to tai­lor plant­i­ngs to their prop­er­ties and reveg­e­tate areas scoured dur­ing T.S. Irene. They will also con­tinue mon­i­tor­ing the site.

Long-term mon­i­tor­ing wells were installed on a major fail­ing hill­s­lope at the site, and a sep­a­rate phase of restora­tion is being planned for that hill­s­lope in 2016.

The stream restora­tion was funded by the New York City Depart­ment of Envi­ron­men­tal Pro­tec­tion and the Nat­ural Resources Con­ser­va­tion Ser­vice Emer­gency Water­shed Pro­tec­tion pro­gram. The Town of Hunter spon­sored the project.

Over the past four years, AWSMP has pro­vided local match to fed­eral funds to com­plete six stream restora­tion projects total­ing $6.8 mil­lion in the Stony Clove Creek water­shed. The AWSMP is a part­ner­ship between Cor­nell Coop­er­a­tive Exten­sion of Ulster County, Ulster County SWCD, and New York City Depart­ment of Envi­ron­men­tal Protection.

The AWSMP plans to carry out a stream restora­tion project in the Beaver Kill Water­shed in the Town of Wood­stock in 2017.

Stony Clove Creek near Wright Road looking upstream before steam restoration.

Stony Clove Creek near Wright Road look­ing upstream before steam restoration.

 

Stony Clove Creek near Wright Road looking upstream during steam restoration.

Stony Clove Creek near Wright Road look­ing upstream dur­ing steam restoration.

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