Estimation of bankfull discharge based on stream channel characteristics in Garmabdasht Catchment, Golestan Province

Document Type : Full length article


1 Assistant Professor of Geomorphology, University of Mazandaran, Iran

2 M.Sc. of Geomorphology, University of Mazandaran, Iran


The bankfull discharge corresponds to the river level just before it starts to flow out of its main channel and over its floodplain (Navratil et al., 2006). Bankfull discharge is a deterministic discharge often used to estimate the channel-forming discharge. It is adopted that the bankfull discharge (magnitude and frequency) is one of the important concepts in the analysis of river morphology, flood events and ecological systems. River geomorphologists are particularly interested in bankfull discharge because it serves as a consistent morphological index that can be applied in river engineering and stream restoration to design a stable size and shape for a stream so that its channel will maintain its dimensions, pattern, and profile over time without degrading or aggrading (Rosgen, 1994; Knighton, 1996). Bankfull hydraulic geometry relationships vary by region along with changes in hydrology, soils, and land uses (Doll et al., 2002). This study investigates spatial changes in the bankfull hydraulic geometry such as width, depth and cross section area with bankfull discharge and catchment area.
Garmab-Dasht catchment is located in the northeastern Alborz, Golestan province and south east Gorgan. The study area geologically consists of marine and continental sequences, which deposited through the Msozoic to Cenozoic. The altitude of the Garmab-Dasht catchment varies from a maximum of 3400 m to 400 m on the valley floor. Mean annual rainfall in the catchment is around 550 mm. Mean annual discharge of main stream is measured 0.58 m3/s.
Materials and Methods
In this research, Garmabdasht catchment is divided into eleven reaches. Several criteria have been identified to assist in field identification of the bankfull stage. It contains significant breaks in slope, changes in vegetation, the highest scour line, and the top of the bank. Field measurements of bankfull width (W), bankfull depth (d) channel slope (S), bankfull cross-sectional area and streambed-material sizes (Di) were conducted at each site. Two or three width measurements per channel reach were conducted and a mean width per reach was calculated. The grain sizes of surface sediments were sampled along the channel by pebble count method. After data collection, hydraulic geometry relationships calculated for bankfull discharge, cross-sectional area, width, and mean depth as functions of watershed area for the Garmab Dasht catchment. Flood frequency analysis is used to estimate the recurrence of bankfull discharge by a 30 years Annual Maximum Series (AMS).
Results and Discussion
The relationships between channel-morphology characteristics and bankfull discharges were examined using the power function regression equations. The high coefficients of determination indicate good agreement between the measured data and the best-fit relationships. The exponent value of width and depth were obtained 0.42 and 0.34, respectively. It shows that channel width increases more rapidly with the area than channel depth. Also, values of shear stress and stream power at bankfull condition represent a power function regression with catchment area. The study reaches show a good relationship between cross section area, bankfull discharge and drainage area, through the linear regression with a high R2 (0.95). Shear stress and stream power show a power regression with catchment area. Also, stream power has a good relationship with bankfull width (R2 = 0.74). The empirical equations expressing the relationships between Di (in m) and drainage area is calculated as power regression. But, correlation results give no significant p level (P>0.05) for Di and drainage area. Many research show that there are relationships between bankfull hydraulic geometry (width, depth, cross section area) and drainage area (Harman et al., 1999; Vianello & D'Agostino, 2007; Mulvihill & Baldigo, 2012; Modrick & Georgakakos, 2014). The results of this study verify such relations in Garmab-Dasht catchment. 
Log-Pearson Type III distributions were used to analyze annual peak discharge data for Garmab Dasht gage station. Many studies have found that bankfull discharge occurs at a recurrence interval of about 1–2 years on the basis of the annual maximum series (AMS) approach (Leopold et al., 1964; Dury, 1976; Castro & Jackson, 2001, Navratil et al., 2006; Schneider, 2011). The recurrence interval for the bankfull discharge in study area obtained 2 years.
The results of the regression analyses indicated that Bankfull width, bankfull depth, bankfull cross-sectional area, and bankfull discharge were related to drainage area using regression analysis. Bankfull hydraulic geometry relationships can be used to estimate the bankfull discharge at an ungaged site. Also, it can be toassist in field identification of bankfull stage and dimension in un-gaged watersheds. Further work is necessary to develop reliable relationships for other regions and rainfall/runoff conditions of Iran.


Main Subjects

اسماعیلی، ر.؛ حسین‌زاده، م.م. و متولی، ص. (1390). تکنیک‌هایمیدانیدرژئومورفولوژیرودخانه‌ای، تهران: لاهوت.
متولی، ص.؛ حسین‌زاده، م.م. و اسماعیلی، ر. (1392). ارتباط دبی لبالبی با واحدهای ژئومورفیک در رودخانه‌های کوهستانی، مطالعة موردی: رودخانة لاویج در دامنة شمالی البرز مرکزی، پژوهش‌هایدانشزمین، 4(14): 17 ـ 33.
Bhatt, V.K. and Tiwari, A.K. (2008). Estimation of peak streamflows through channel geometry, Hydrol Sci J, 53(2):401-408.
Cinotto, P.J. )2003). Development of regional curves of bankfull-channel geometry and discharge for streams in the non-urban, Piedmont Physiographic Province, Pennsylvania and Maryland: U.S. Geological Survey Water-Resources Investigations Report 03-4014, 33 p.
Emmett, W.W. and Wolman, M.G. (2001). Effective discharge and gravel-bed rivers, Earth Surface Processes and Landforms, 26: 1369-1380.
Esmaili, R.; Hosseinzadeh, M.M. and Motevalli, S. (2011). Field technique in fluvial geomorphology, Lahut, Tehran (In Persian).
Faustini, J.M.; Kaufmann, F.R. and Herlihy, A.T. (2009). Downstream variation in bankfull width of wadeable streams across the conterminous United States, Geomorphology, 108: 292-311.

Heitmuller, F.T.; Hudson, P.F. and Asquith, W.H. (2015). Lithologic and hydrologic controls of mixed alluvial–bedrock channels in flood-prone fluvial systems: Bankfull and macrochannels in the Llano River watershed, central Texas, USA, Geomorphology, 232: 1-19.

Harman, W.A.; Jennings, G.D.; Patterson, J.M.; Clinton, D.R.; Slate, L.O.; Jessup, A.G.; Everhart, J.R. and Smith, R.E. (1999). Bankfull hydraulic geometry relationships for North Carolina streams. In: Olsen, D.S., Potyondy, J.P. (Eds.), Wildland Hydrology, AWRA Symposium Proceedings, American Water Resources Association, Bozeman, MT, pp. 401-408.
Johnson, M.H. (2003). Development of a Regional Curve to Relate Discharge and Drainage Area to Hydraulic Geometry for the Red River of the North Basin, University of North Dakota, Grand Forks, ND, Master's Thesis.
Johnson, B.H. and Padmanabhan, G. (2010). Regression estimates of design flows for ungaged sites using bankfull geometry and flashiness, Catena, 81: 117-125.
Modrick, T.M. and Georgakakos, K.P. (2014). Regional bankfull geometry relationships for southern California mountain streams and hydrologic applications, Geomorphology, 221: 242-260.
Montgomery, D.R. and Gran, K.B. (2001). Downstream variations in the width of bedrock channels, Water Resources Research, 37(6): 1841-1846.
Mulvihill, C.I. and Baldigo, B.P. (2012). Optimizing bankfull discharge and hydraulic geometry relations for streams in New York State, Journal of the American water resources association, 48(3).
Mulvihill, C.I.; Baldigo, B.P.; Miller, S.J.; DeKoskie, D. and DuBois, J. (2010). Bankfull discharge and channel characteristics of streams in New York State,Scientific Investigations Report 2009-5144, U.S. Geological Survey, Reston, Virginia, pp 51.
Motevalli, S.; Hosseinzadeh, M.M. and Esmaili, R. (2013). Relation of bankfull width with morphological units in mountain stream: Case study, Lavij River in north slope of Central Alborz, 14: 17-33 (In Persian).
Petit, F. and Pauquet, A. (1997). Bankfull discharge recurrence interval in gravel-bed rivers, earth surfaces processes and landforms, 22: 685-693.
Pietsch, T.J. and Nanson, G.C. (2011). Bankfull hydraulic geometry; the role of in-channel vegetation and downstream declining discharges in the anabranching and distributary channels of the Gwydir distributive fluvial system, southeastern Australia, Geomorphology, 129: 152-165.
Schneider, C.; Flörke, M.; Eisner, S. and Voss, F. (2011). Large scale modelling of bankfull flow: An example for Europe, Journal of Hydrology, 408: 235-245.
Sweet, W.V. and Geratz, G.W. (2003). Bankfull hydraulic geometery relationships and recurrence intervals for north Carolina’s coastal plain, Journal of the American Water Resources Association, 39(4): 861-871.
Tayfur, G. and Singh, V.P. (2011). Predicting Mean and Bankfull Discharge from Channel Cross-Sectional Area by Expert and Regression Methods, Water Resour Manage, 25: 1253-1267.
Vianello, A. and D'Agostino, V. (2007). Bankfull width and morphological units in an alpine stream of the dolomites (Northern Italy), Geomorphology, 83: 266-281.
White, K.E. (2001). Regional curve development and selection of a reference reach in the non-urban lowland sections of the Piedmont Physiographic Province, Pennsylvania and Maryland: U.S. Geological Survey Water-Resources Investigations Report 01-4146, 20 p.
Williams, G.P. (1978). Bankfull discharge of rivers, Water Resour. Res., 14(6): 1141-1153.
Wu, B.; Wang, G.; Xia, J.; Fu, X. and Zhang, Y. (2008). Response of bankfull discharge to discharge and sediment load in the Lower Yellow River, Geomorphology, 100: 366-376.
Xia, J.; Wu, B.; Wang, G. and Wang, Y. (2010). Estimation of bankfull discharge in the Lower Yellow River using different approaches, Geomorphology, 117: 66-77.
Volume 48, Issue 3
October 2016
Pages 451-463
  • Receive Date: 04 April 2015
  • Revise Date: 23 February 2016
  • Accept Date: 16 March 2016
  • First Publish Date: 22 September 2016