Investigating Role of Vegetation in Protection of Houses during Floods

Amina Ali, Ghufran Ahmad Pasha, Usman Ghani, Afzal Ahmed, Fakhar Muhammad Abbas


Flood flows have the potential to cause substantial damage to infrastructure, mankind, livestock and agricultural land which all stacks up to greatly affect the financial condition of the region. During 2010 Pakistan floods, more than two million houses were damaged partly or totally [1]. To minimize these types of destructions, inland vegetation can be considered a natural barrier to dissipate the energy of flood flow and limits widespread inundation. This study involves volume of fluid (VOF) modelling approach to figure out the role of vegetation of finite width in energy reduction of flood flow, in front of houses, against: vegetation of varying Aspect Ratio (A/R width-length ratio) and distance between vegetation & houses (Lr). Channel domain was built in ANSYS workbench toolkit and meshing was done in meshing building toolkit. For the postprocessing and simulation, FLUENT was used. Various contour plots & profiles of cross stream-wise velocities and water level measurements are presented in this paper. The simulation results of cross stream-wise velocities and water level measurements were identical with experimental data. At vegetation upstream and downstream, velocity reduction observed in higher A/R (2.40) compared to vegetation of A/R-1. Whereas, outside the vegetation and near the walls of channel domain flow velocities were high. The water level was raised on the upstream side of the vegetation due to resistance offered by vegetation. On the upstream side of vegetation, the rise in backwater depth increased by increasing A/R. Contrarily, on the downstream side of vegetation, an undular hydraulic jump was observed in between vegetation and a house. By increasing A/R, the energy loss increases under constant vegetation conditions (G/d = 0.24, Fro = 0.70; G = spacing of each cylinder in cross-stream direction and d= diameter of cylinder and Fro = initial Froude number) and increase in house distance from 1W to 2W, the energy reduction increased from 2.40% to 3.15% which was further increased to 5.04% for another 5W increase in house distance, where W is the vegetation width. Simulation results also shown that with increasing Froude no from 0.60 to 0.70 water level depth has also an incremental pattern which ultimately results in increase in energy dissipation along the varying building distance (1W, 2W & 5W).  Thus, to minimize the structural damage, a structure must be located at a safe distance away from the vegetation where flow becomes sub-critical.


VOF Modeling; Vegetation; Flood; k-ε Turbulence Model; Aspect Ratio.


Shah, Attaullah, Hamid Khan, and Ehsan Qazi. "Damage assessment of flood affected mud houses in Pakistan." Journal of Himalayan Earth Sciences 46, no. 1 (2013).

Pasha, Ghufran Ahmed, and Norio Tanaka. “Undular Hydraulic Jump Formation and Energy Loss in a Flow through Emergent Vegetation of Varying Thickness and Density.” Ocean Engineering 141 (September 2017): 308–325. doi:10.1016/j.oceaneng.2017.06.049.

Smith, Bronte. "The role of vegetation in catastrophic floods: A spatial analysis.", University of Wollongong (2013).

Irtem, Emel, Nuray Gedik, M. Sedat Kabdasli, and Nilay E. Yasa. “Coastal Forest Effects on Tsunami Run-up Heights.” Ocean Engineering 36, no. 3–4 (March 2009): 313–320. doi:10.1016/j.oceaneng.2008.11.007.

Tanaka, Norio, Junji Yagisawa, and Satoshi Yasuda. “Breaking Pattern and Critical Breaking Condition of Japanese Pine Trees on Coastal Sand Dunes in Huge Tsunami Caused by Great East Japan Earthquake.” Natural Hazards 65, no. 1 (September 7, 2012): 423–442. doi:10.1007/s11069-012-0373-4.

Tanaka, Norio, Hajime Sato, Yoshiya Igarashi, Yuya Kimiwada, and Hiroyuki Torita. “Effective Tree Distribution and Stand Structures in a Forest for Tsunami Mitigation Considering the Different Tree-Breaking Patterns of Tree Species.” Journal of Environmental Management 223 (October 2018): 925–935. doi:10.1016/j.jenvman.2018.07.006.

Anjum, Naveed, Usman Ghani, Ghufran Ahmed Pasha, Muhammad Usman Rashid, Abid Latif, and M. Zubair Yousaf Rana. “Reynolds Stress Modeling of Flow Characteristics in a Vegetated Rectangular Open Channel.” Arabian Journal for Science and Engineering 43, no. 10 (April 2, 2018): 5551–5558. doi:10.1007/s13369-018-3229-8.

Jiang, Beihan, Kejun Yang, and Shuyou Cao. “An Analytical Model for the Distributions of Velocity and Discharge in Compound Channels with Submerged Vegetation.” Edited by Vanesa Magar. PLOS ONE 10, no. 7 (July 10, 2015): e0130841. doi:10.1371/journal.pone.0130841.

Tanaka, Tomohiro, Yasuto Tachikawa, Yutaka Ichikawa, and Kazuaki Yorozu. “Impact Assessment of Upstream Flooding on Extreme Flood Frequency Analysis by Incorporating a Flood-Inundation Model for Flood Risk Assessment.” Journal of Hydrology 554 (November 2017): 370–382. doi:10.1016/j.jhydrol.2017.09.012.

Faisal, I.M, M.R Kabir, and A Nishat. “Non-Structural Flood Mitigation Measures for Dhaka City.” Urban Water 1, no. 2 (June 1999): 145–153. doi:10.1016/s1462-0758(00)00004-2.

Nepf, H. M. “Drag, Turbulence, and Diffusion in Flow through Emergent Vegetation.” Water Resources Research 35, no. 2 (February 1999): 479–489. doi:10.1029/1998wr900069.

Wu, Fu-Chun, Hsieh Wen Shen, and Yi-Ju Chou. "Variation of roughness coefficients for unsubmerged and submerged vegetation." Journal of hydraulic Engineering 125, no. 9 (1999): 934-942. doi:10.1061/(ASCE)0733-9429(1999)125:9(934).

Iimura, Kosuke, and Norio Tanaka. “Numerical Simulation Estimating Effects of Tree Density Distribution in Coastal Forest on Tsunami Mitigation.” Ocean Engineering 54 (November 2012): 223–232. doi:10.1016/j.oceaneng.2012.07.025.

Huai, Wenxin, Yang Hu, Yuhong Zeng, and Jie Han. “Velocity Distribution for Open Channel Flows with Suspended Vegetation.” Advances in Water Resources 49 (December 2012): 56–61. doi:10.1016/j.advwatres.2012.07.001.

Schoneboom, Thomas, Jochen Aberle, and Andreas Dittrich. "Hydraulic resistance of vegetated flows: Contribution of bed shear stress and vegetative drag to total hydraulic resistance." River Flow 2010 (2014): 269-276.

Carollo, Francesco Giuseppe, V. I. T. O. Ferro, and D. Termini. "Flow velocity measurements in vegetated channels." Journal of Hydraulic Engineering 128, no. 7 (2002): 664-673. doi:10.1061/(ASCE)0733-9429(2002)128:7(664).

Smith, R.J., N.H. Hancock, and J.L. Ruffini. “Flood Flow through Tall Vegetation.” Agricultural Water Management 18, no. 4 (November 1990): 317–332. doi:10.1016/0378-3774(90)90014-p.

Tanaka, Norio, and Junji Yagisawa. “Effects of Tree Characteristics and Substrate Condition on Critical Breaking Moment of Trees Due to Heavy Flooding.” Landscape and Ecological Engineering 5, no. 1 (January 15, 2009): 59–70. doi:10.1007/s11355-008-0060-5.

Pasha, Ghufran Ahmed, Norio Tanaka, Junji Yagisawa, and Fuadi Noor Achmad. “Tsunami Mitigation by Combination of Coastal Vegetation and a Backward-Facing Step.” Coastal Engineering Journal 60, no. 1 (January 2, 2018): 104–125. doi:10.1080/21664250.2018.1437014.

Santos, Angela, Nuno Fonseca, Margarida Queirós, José Zêzere, and José Bucho. “Implementation of Tsunami Evacuation Maps at Setubal Municipality, Portugal.” Geosciences 7, no. 4 (November 8, 2017): 116. doi:10.3390/geosciences7040116.

Wüthrich, Davide, Michael Pfister, Ioan Nistor, and Anton J. Schleiss. “Effect of Building Overtopping on Induced Loads During Extreme Hydrodynamic Events.” Journal of Hydraulic Research (March 29, 2019): 1–16. doi:10.1080/00221686.2019.1573764.

Adriano, Bruno, Satomi Hayashi, and Shunichi Koshimura. “Analysis of Spatio-Temporal Tsunami Source Models for Reproducing Tsunami Inundation Features.” Geosciences 8, no. 1 (December 25, 2017): 3. doi:10.3390/geosciences8010003.

Macabuag, Joshua, Tiziana Rossetto, Ioanna Ioannou, and Ian Eames. “Investigation of the Effect of Debris-Induced Damage for Constructing Tsunami Fragility Curves for Buildings.” Geosciences 8, no. 4 (March 31, 2018): 117. doi:10.3390/geosciences8040117.

Paulik, Ryan, Emily Lane, Shaun Williams, and William Power. “Changes in Tsunami Risk to Residential Buildings at Omaha Beach, New Zealand.” Geosciences 9, no. 3 (March 2, 2019): 113. doi:10.3390/geosciences9030113.

Chiew, Yee-Meng, and Soon-Keat Tan. "Frictional resistance of overland flow on tropical turfed slope." Journal of hydraulic engineering 118, no. 1 (1992): 92-97. doi:10.1061/(ASCE)0733-9429(1992)118:1(92).

Gao, Guanghai, Roger A. Falconer, and Binliang Lin. "Modelling open channel flows with vegetation using a three-dimensional model." Journal of Water Resource and Protection 3, no. 02 (2011): 114.

Järvelä, Juha. “Determination of Flow Resistance Caused by Non‐submerged Woody Vegetation.” International Journal of River Basin Management 2, no. 1 (March 2004): 61–70. doi:10.1080/15715124.2004.9635222.

Meftah, M. Ben, F. De Serio, D. Malcangio, A. F. Petrillo, and M. Mossa. "Experimental study of flexible and rigid vegetation in an open channel." In Proc. River Flow, vol. 1 (2006): 603-611.

Cuomo, Giovanni, Gholamreza Shams, Sebastian Jonkman, and Pieter van Gelder. “Hydrodynamic Loadings of Buildings In Floods.” Coastal Engineering 2008 (May 2009): 3744–56. doi:10.1142/9789814277426_0310.

Pakoksung, Kwanchai, Anawat Suppasri, and Fumihiko Imamura. “Systematic Evaluation of Different Infrastructure Systems for Tsunami Defense in Sendai City.” Geosciences 8, no. 5 (May 10, 2018): 173. doi:10.3390/geosciences8050173.

Anjum, Naveed, Usman Ghani, Ghufran Ahmed Pasha, Abid Latif, Tahir Sultan, and Shahid Ali. “To Investigate the Flow Structure of Discontinuous Vegetation Patches of Two Vertically Different Layers in an Open Channel.” Water 10, no. 1 (January 16, 2018): 75. doi:10.3390/w10010075.

Pasha, Ghufran Ahmed, and Norio Tanaka. “Effectiveness of Finite Length Inland Forest in Trapping Tsunami-Borne Wood Debris.” Journal of Earthquake and Tsunami 10, no. 04 (October 2016): 1650008. doi:10.1142/s1793431116500081.

Chow, Ven T. "Open-channel hydraulics." McGraw-Hill Civil Engineering Series, McGraw-Hill: Tokyo. xviii, 680 pp. (1959).

Full Text: PDF

DOI: 10.28991/cej-2019-03091436


  • There are currently no refbacks.

Copyright (c) 2019 amina ali, ghufran ahmad, Fakhar muhammad abbas

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.