Posts Tagged ‘stream stability’

Monday’s Bankfull Flows

Posted on: December 4th, 2020 by Tim Koch

Monday November 30th, 2020 was a rainy day in the Ashokan watershed. A home rain gauge in Boiceville measured approximately 4 inches over the course of the day.

In response to the significant precipitation the Beaver Kill, Little Beaver Kill, Bushkill, and Esopus Creek at Cold Brook reached bankfull discharge. Bankfull discharge is the stream flow that completely fills the channel in a geomorphically stable stream. Any flow that exceeds bankfull will put water onto the adjacent floodplain.

Cross section of a geomorphically stable stream where the entire channel is filled during a bankfull flow.

Streams that have berms or levees, are incised, or otherwise unstable do not have such a clear relationship between bankfull discharge and channel geometry.

In the Northeast, a bankfull or greater flow happens once every 1.5 years, on average. However, “on average” means that some years see multiple bankfull events while others have none. Monday’s event was the second time in 2020 that the Little Beaver Kill has equaled or exceeded its bankfull discharge of 909 cubic feet per second (cfs).

2020 Hydrograph of the Little Beaver Kill. From USGS.

Bankfull flow events are important because over time, these flows move more sediment than any other discharge, larger or smaller. This is because bankfull flows happen regularly, every 1.5 years on average, as opposed to big floods that move a lot of sediment but are more infrequent.

Due to the geomorphic importance of bankfull discharge events, the AWSMP regularly visits stream restoration sites, culvert replacement projects, and other stream reaches following bankfull events to take photographs and monitor any changes observed in the channel.

AWSMP staff from the Ulster County Soil & Water Conservation District inspect a restoration site on Woodland Creek following a bankfull flow in November 2019. Photo by Tim Koch.

New Video on Stream Channel Stability

Posted on: May 6th, 2020 by Tim Koch

The AWSMP office might be physically closed, but our education staff have been hard at work generating online stream based content for both youth and adults.

AWSMP Educators Matt Savatgy, Brent, Gotsch, Tim Koch, and Amanda Cabanillas.

AWSMP Educators (from left to right) Matt Savatgy, Brent Gotsch, Tim Koch, and Amanda Cabanillas during a snowshoe stream walk in 2019.

 

AWSMP Stream Educator Tim Koch has just released a new video on stream channel stability: what it is, and why it is important to maintain and improve the stability of our rivers and streams. This 9-minute video is meant for landowners, municipal officials, conservation advisory council members, and anyone else interested in or involved in stream management.

 

This video can also be viewed directly from AWSMP’s YouTube Channel.

AWSMP Watershed Youth Educator Matt Savatgy and Program Assistant Amanda Cabanillas are currently producing a series of educational videos and at-home activities for students. Follow along at home as they discuss different types of rocks, assess a culvert, and investigate stream features in a channel cross-section.

 

Screenshot of CCE Ulster Youth Education Video Series Website

Screenshot of CCE Ulster Youth Science Education Video Series Website

 

The online science series can be found at the Cornell Cooperative Extension of Ulster County website and on the AWSMP website under Videos.

Check back with us in the coming weeks, especially if you are a streamside landowner or own property in the Special Flood Hazard Area as Resource Educator Brent Gotsch will be producing a series of short videos on floodplains, floodproofing, and all things flood insurance. In these upcoming videos, Brent will teach viewers how to read a flood insurance rate map (FIRM) and the workings of the National Flood Insurance Program (NFIP) among other flood related topics.

As always, our education and technical staff are available to answer any stream, floodplain, or riparian buffer related questions! Call the AWSMP office main line at (845) 688-3047 for assistance or email info@ashokanstreams.org.