Advice, methods and tools for estimating channel roughness

C McGahey, Donald Knight, PG Samuels

Research output: Contribution to journalArticle

12 Citations (Scopus)


Roughness plays an essential role in water level estimation for rivers, watercourses and drains. It reduces the discharge capacity through energy expenditure from boundary-generated turbulence as well as physical blockages caused by vegetation. Today's practitioners are constantly challenged with identifying, quantifying and simulating these processes to provide vital information for a range of flood risk management tasks. This paper introduces the roughness advisor, one of a series of tools embedded in the recently developed Environment Agency's conveyance and afflux estimation system. The roughness advisor provides an extensive database of roughness information from a diverse set of sources (>700) and presents it in a structured manner to enable users readily to select from a range of in-channel and floodplain vegetation and bed material types. Traditionally, flow resistance datasets are based on average values of Manning's n for whole river sections. Here, the notion of a local unit roughness n(l) is introduced and its performance is demonstrated through flow prediction for a range of channel types. Further applications are used to compare the unit roughness with the traditional Manning n, to trial a boulder roughness approach and to describe the sensitivity and relative importance of roughness in the calculation of channel flow.
Original languageEnglish
Pages (from-to)353-362
Number of pages10
JournalWater Management
Issue number6
Publication statusPublished - 1 Dec 2009


  • hydraulics & hydrodynamics
  • river engineering
  • floods & floodworks


Dive into the research topics of 'Advice, methods and tools for estimating channel roughness'. Together they form a unique fingerprint.

Cite this