Stream Channel Terminology Rosgen 1998 photos diagrams content

Stream Channel Terminology Rosgen (1998) – photos, diagrams, content Bob Gubernick – content

Wetted vs. Bankfull Channel • Wetted Channel – Portion of the stream channel covered in water – Fluctuates with hydrologic changes – Perform survey at baseflow to get comparable data • Bankfull Channel – Channel that contains bankfull discharge – Bankfull discharge is the discharge that fills a stable channel to the elevation of the active floodplain – Return interval 1. 1 -2 yrs, 65% chance each year, can happen several times per yr

Wetted vs. Bankfull Channel • Wetted Channel – Estimated width – Max and ave depth – Dom and substrate • Bankfull Channel – – Bank instability LWD Channel width Riparian width

Wetted vs. Bankfull Channel Bankfull Width Wetted Width

Is it always that easy?

Where’s bankfull? • It’s not always easy to find • Sometimes we need bankfull indicators…

Bankfull indicators • Flat depositional areas next to active channel – Sand deposits – Break in slope of banks • Top of depositional feature (point bars)

Bankfull indicators • Look at the ‘big picture’ – use the entire channel and a combination of indicators • Focus on areas with uniform flow, especially riffles with few irregularities • Often not clear around culverts, bridges, tributaries, large wood

Top of bank = bankfull

Top of point bar = bankfull

Break in bank slope = bankfull

Top of point bar = bankfull

Bankfull Measurements • Always use areas with uniform channel – Straight riffles or runs are best • Do not use irregular areas – – – Pools or glides Meanders or bends Tributary or side channel confluences Road/trail crossings Large wood jams

Where to measure

Where to measure

Bankfull Example

Bankfull Quiz