Geomorphological equilibrium by Rosgen and River Style Framework methods (Case study: Tarwal River, Kurdistan)

Document Type : Full length article


1 Assistant Professor of Geomorphology, Faculty of Natural Resources, University of Kurdistan, Iran

2 Assistant Professor of Range and Watershed Management, Faculty of Natural Resources, University of Kurdistan, Iran

3 MSc in Natural Hazards, Faculty of Natural Resources, University of Kurdistan, Iran


There are many different factors changing rivers in terms of size, shape, direction and pattern. These changes highlight that rivers tend to equilibrate. The balance between erosion and deposition in a river is defined as equilibrium while the stability of stream morphology is defined as the ability to resist morphological changes for a long time. Doyle and Harbor (2003) showed that bed sediments type has a great impact on the equilibrium, so that the time needed for a sandy-bed channel to equilibrate is almost half of that needed for a gravel-bed channel. It’s because sediments transport more rapidly in sandy-bed channels and such channels equilibrate faster than those having fine sediments. A well-known method to evaluate river stability is Rosgen stream classification system. Savery et al (2007) reported that Rosgen stream classification system is applicable for flat and low steep areas. This method is applicable in river engineering designs, management purposes and stream restoration. River Style Framework method is another applicable method to evaluate river stability. Equilibrium, stability and the role of environmental variables on Tarwal River have not been studied yet. As a result, there is no proper knowledge of its equilibrium and stability. Therefore, this case study is trying to study the equilibrium and stability issues in Tarwal basin.
Materials and methods
This case study demonstrates the capabilities of Rosgen and River Style Framework methods in Tarwal River, the main tributary of Sefid Rud. The tributary is located in the eastern part of Kurdistan province. For each river style segment of Tarwal River network, equilibrium capacity and geomorphic conditions have been determined by river style framework using three parameters of channel properties, channel planform and bed characteristics. In the next step, stability of Tarwal River has been determined by Rosgen stream classification system using 15 parameters (bank vegetation, channel capacity, section cuts, aggradation, degradation, sediment and etc.). In addition to extensive field campaigns, topographic maps, aerial photos and Google Earth software have been used to determine cross section dimensions and vegetation condition as well as trenches and terraces. During field campaigns, cross sections dimensions have been measured by a laser meter Leica D5 and locations of sections and trenches have been recorded by GPS. Then, the data have been digitized by ArcGIS. Furthermore, required photos have also been collected from different features in situ.
Results and discussion
Based on river style framework method, river style segments of fine-grained bed having low sinuosity, clay-bed and sandy-bed meandering have represented a local equilibrium capacity. These rivers style segments have indicated limited vertical and lateral movements and their sediments sorted well while river style segments of gravel-bed having low sinuosity or sandy-bed multichannel in Ozon Darreh River, sandy-bed with low sinuosity in Tarwal River and fine-grained meandering in Sang Siah River all have indicated a high equilibrium capacity. This is because of vertical and lateral movements and non-homogeneous sediments. In fine-grained meandering river style segments of Sang Siah River, equilibrium capacity was increased because of vertical (bed incision) and lateral movements in the form of channel contraction (alluvial terraces). This was dominated by vertical movements. These results support Nayyeri and Rezaei Moghadam (2005) findings in meandering river of Siminehrood where bed equilibrium reported as the form of bed incision. By River Style Framework method, the geomorphic conditions of the river were assessed through river characteristics and behavior. River style segments of gravel-bed river with low sinuosity in Sis River and a small tributary (in the northeast part of Tarwal River), a sandy-bed river with low sinuosity in Tarwal River and sandy-bed multichannel in Ozon Darreh River have represented a relatively high width to depth ratio, low sinuosity, compound and irregular channel shapes and erosional banks. These river style segments have represented poor geomorphic conditions because of non-homogenous poor-sorting sediments and bed erosion. River style segments of fine-grained bed with low sinuosity in Esmail Jamal, Jorvandi, Ozon Darreh and Tarwal Rivers, clay-bed ada in Sang Siah and Jorvandi Rivers and sandy-bed meandering in Tarwal River have also indicated a good geomorphic condition because of well-sorted sediments, considerable vegetation cover and lack of erosional banks.
The stability of all sections has been analyzed by Rosgen stream classification system. For this purpose, each river style segment, 1-3 sections (totally 34 sections) have been studied and their dimensions measured in situ. River style segments of clay-bed ada in Sang Siah River with sandy-bed meandering, sandy-bed multichannel, fine-grained river with low sinuosity and fine-grained meanders in Tarwal Main River are stable while river style segments of gravel-bed river with low sinuosity in Sis and a small tributary (in the northeast of Tarwal River), sandy-bed with low sinuosity in Tarwal River and sandy-bed multichannel in Ozon Darreh River are unstable. This instability is because of significant incision, high roundness of sediments grain distribution and their poor sorting as well as filled pools.  
Instability of River style segment in downstream Jorvandi and Ozon Darreh Rivers and upstream Tarwal and Sang Siah Rivers might be related to numerous faults in some sections. Increase in sediment size is a good evidence of recent faulting activities in these sections. Faults possibly increase stream channel slope that results in increased velocity of streamflow and creating unstable reaches. Increasing streamflow velocity causes considerable movements of sediments so as fine sediments washed out and only coarse sediments remain in the streambed. Such evidences supports that the riverbed of these segments has affected small-scale tectonic activities. Due to non-steepness of the study area, Rosgen stream classification system is suitable for the field data very well. This supports Savery et al (2007)’s recommendation about benefits of Rosgen method in flat areas. The results of this study can help us improve integrated evaluation of watershed management activities, hydrological designs and river rehabilitation projects.


Main Subjects

اسماعیلی، ر. و حسین‏زاده، م.‏م. (1394). مقایسة روش‏های روزگن و چهارچوب استیل رود در طبقه‏بندی رودخانه‏های کوهستانی، مطالعة موردی البرز شمالی، حوضة آبریز لاویچ، پژوهش‏های دانش زمین، 6(21): 64ـ79.
بابایی، ه. و لشکرآرا، ب. (1394). به‏کارگیری تئوری رزگن در طبقه‏بندی رودخانه (مطالعة موردی: رودخانة کاکارضا)، دهمین کنگرة بین‏المللی مهندسی عمران، دانشکدة مهندسی عمران، تبریز.
حسین‏زاده، م.م.؛ اسماعیلی، ر. و متولی، ص. (1384). بررسی کارایی طبقه‏بندی رزگن (مطالعة موردی: طبقه‏بندی رودخانه‏های بابل و تالار در محدودة جلگة ساحلی خزر)، فصل‏نامة جغرافیایی سرزمین، 2(5).
دفتر فنی معاونت برنامه‏ریزی و نظارت راهبردی رئیس جمهور (1391). راهنمای مطالعات ریخت‏شناسی رودخانه‏ها، نشریة شمارة 592.
رامشت، م.ح. (1391). نقشه‏های ژئومورفولوژی (نمادها و مجازها)، تهران: سمت.
رضایی‏مقدم، م.ح.؛ ثروتی، م.ر. و اصغری سراسکانرود، ص. (1391). بررسی تغییرات شکل هندسی رودخانة قزل‏اوزن با تأکید بر عوامل ژئومورفیک و زمین‏شناسی، جغرافیا و برنامه‏ریزی محیطی، 23(2): 1ـ14.
روستایی، ش.؛ خورشیددوست، ع.م. و خالقی، س. (1392). ارزیابی مورفولوژی مجرای رودخانة لیقوان با روش راسگن، پژوهش‏های ژئومورفولوژی کمی، 4(1ـ16).
زندی، س. (1394). تأثیر ویژگی‏های ژئومورفولوژیکی بستر رود بر روی کیفیت آب (مطالعة موردی: حوضة رودخانة تروال در استان کردستان)، پایان‏نامة کارشناسی ارشد، دانشکدة منابع طبیعی، دانشگاه کردستان.
لایقی ص. و کرم، ا. (1393). طبقه‏بندی هیدروژئومورفولوژیکی رودخانة جاجرود با مدل روزگن، پژوهش‏های ژئومورفولوژی کمی، 3(3): 130ـ143.
نیری، ه. (1389). تحلیل دینامیک و شکل مجرا در حوضة آبریز رودخانة مهاباد، رسالة دکتری، دانشکدة علوم انسانی و اجتماعی، دانشگاه تبریز.
نیری، ه. و رضایی مقدم، م.ح. (1384). تغییرات ژئومورفولوژیک مجاری آبرفتی دشت سیلابی زرینه‏رود و سیمینه‏رود و مخاطرات ناشی از آن‏ها، کنفرانس مخاطرات زمین، بلایای طبیعی و راهکارهای مقابله با آن، دانشکدة علوم انسانی و اجتماعی، دانشگاه تبریز.
یمانی، م. و تورانی، م. (1393). طبقه‏بندی ژئومورفولوژیکی الگوی آبراهة طالقان‏رود در محدودة شهرک طالقان از طریق روش رزگن، پژوهش‏های جغرافیای طبیعی، 2(183ـ198).
یمانی، م.؛ مقصودی، م.؛ محمدخان، ش. و مرادی، ا. (1394). طبقه‏بندی مورفولوژیکی آبراهة رودخانة تلوار بر اساس روش رزگن و کارایی آن (حد فاصل روستای کچی‏گرد تا حسن‏خان)، پژوهش‏های دانش زمین، 23: 1ـ18.
Angela C.B.; Javier C.J.; Teresa G.M. and Marisa, M.H. (2015). Hydrological evaluation of a peri-urban stream and its impact on ecosystem services potential, Global Ecology and Conservation, 3: 628-644.
Babaie, H. and Lashkarara, B. (2015). Using Rosgen theory in river classification, (case study: Kaka Reza River), 10th international congress on civil engineering, Faculty of civil engineering, Tabriz.
Brierley, G. and Fryirs, K. )2005). Geomorphology and River Management: Application of the River Style framework, Blackwell publishing, UK. 398 p.
Department of Technical Affairs, Office of Deputy for Strategic Supervision. (2012). Guideline on the river morphology studies, No. 592.
Doyle, M. and Harbor, J. (2003). A scaling approximation of equilibrium timescales for sand-bed and gravel-bed rivers responding to base-level lowering, Geomorphology, 54: 217-223.
Esmaeili, R. and Hosseinzadeh, M.M. ( 2015). Comparison of Rosgen and the river style framework methods for the classification of mountainous rivers, case study: northern Alborz, Lavij basin, Journal of earth science researches, sixth year, 21: 64-79.
Fryirs, K. and Brierley, G. (2000). A Geomorphic approach to the identification of river recovery potential, Physical Geography, 21: 244-277.
Hosseinzadeh, M.M.; Esmaeili, R. and Motavali, S. (2005). Assessment the efficiency of the Rosgen classification, (case study: classification of the Babel and Talar rivers, the Khazar coastal plain), Quarterly Geographical Journal of Territory, 2(5).
Kasai, M.; Marutani, T. and Brierley, G. (2004). Channel bed adjustments following major aggradation in a steep headwater setting: findings from Oyabu Creek, Kyushu, Japan, Geomorphology, 62: 199-215.
Layeghi, S. and Karam, A. (2014). Hydrogeomorphological classification of Jajroud River by Rosgen model, Quantitative Geomorphological Researches,3(3): 130-143.
Minghui, Yu.; Hongyan, Wei; Yanjie, Liang and Chunyan, Hu. (2010). Study on the Stability of Noncohesive River Bank, International Journal of Sediment Research, 25(4): 391-398.
Mousavi, S.M. (2012). Application of Rosgen classification the Ziarat watershed, Gorgan, Journal of American Science, 8(4): 184-189.
Pregun, C. (2016). Ecohydrological and morphological relationships of a regulated lowland river; based on field studies and hydrological modeling, Ecological Engineering, 94: 608-616.
Nayyeri, H. (2010). Analysis of dynamic and flume form in Mahabad river basin, PHD thesis, Faculty of humanities and social sciences, University of Tabriz.
Nayyeri, H. and Rezai Moghadam, M.H. (2005). Geomorphologic changes of floodplain alluvial flumes of the Zarrinehrood and Siminehrood and their hazard, International Conference of Earth Hazards, Natural Disasters and their Solutions, Faculty of humanities and social sciences, University of Tabriz.
Ramesht, M.H. (2012). Symbols and images in geomorphology, Samt Publication.
Rezaei Moghadam, M.H.; Sarvati, M.R. and Asghari Sareskanrood, S. (2012). Investigation of geometric alterations of Gezel Ozan River considering Geomorphologic and Geologic parameters, Geography and Environmental Planning Journal, 23(2): 1-14.
Roostaei, Sh.; khoshiddoost, A.M. and Khaleghi, S. (2013). Morphological assessment of Lighvan river flume by Rosgen method, Quantitative Geomorphological Researches, 4: 1-16.
Roper, B.; Buffington, J.; Archer, E.; Moyer, Ch.and Ward, M. (2008). The role of observer variation in determining rosgen stream types in northeastern Oregon Mountain streams, JAWRA Journal of the American Water Resources Association, pp. 417-427.
Rosgen, D. (1994). A Classification of Natural Rivers, Catena, 22: 169-199.
Rosgen, D. (1996). Applied River Morphology, Wildland Hydrology Books, Pagosa Springs, Colorado.
Roy, S. and Sahu, A.S. (2016). Effect of land cover on channel form adjustment of headwater streams in a lateritic belt of West Bengal (India), International Soil and Water Conservation Research, in Press:
Savery, T.S.; Belt, G. and Higgins, D. (2007). Evaluation of the Rosgen Stream Classification System in Chequamegon-Nicolet National Forest, Wisconsi, JAWRA Journal of the American Water Resources Association, 37(3): 641-654.
Splinter, D.K. and Dauwalter, D.C. (2016). Frequency of large in-channelwood in eastern Oklahoma ecoregions and its association with channel morphology, Geomorphology, 269: 175-185.
Zandi, S. (2015). The effect of river bed geomorphological features on water quality (Case study: Tarwal river basin in Kurdistan province), Master's thesis, Faculty of Natural Resources, University of Kurdistan.
Yamani, M. and Toorani, M. (2014). Geomorphologic classification of the Taleghanrood stream pattern in the Taleghan city reach by Rosgen metho, Physical geography research quarterly, 2: 183-198.
Yamani, M.; Maghsoudi, M.; Mohammadkhan, Sh. and Moradi, A. (2015). Morphological classification of the Talvar River stream based on Rosgen model and its efficiency (the distance between the Kachigard and Hasankhan villages), Journal of Earth Science Researches, 23: 1-18.