Abstract
A complex coastal environment with a river outlet, a sand spit barrier and an estuary of such coastal features is controlled by wave-induced hydrodynamics and sediment dynamics. The coastal dynamics patterns can be changed by natural or anthropogenic activities. This study is mainly focused on understanding the significant changes of geomorphology, bathymetry, and the coastal dynamics originated due to human influences in a monsoon-affected Kalu Ganga (River) outlet in Sri Lanka. In this research project, bathymetric variations before and after the collapse of sand spit barrier were analysed to understand the extent of the erosional and depositional effects. High-resolution satellite images in Google Earth Pro were also used to qualitatively analyse beach boundary changes before the collapse of the sand spit barrier. Temporal and spatial changes of beach boundary positions after collapse of the sand spit barrier were measured using high precision GPS surveying in river outlet including the evolving sand spit barrier. Nested wave model (Delft3D modelling suite) was applied to understand the wave climate changes. The data obtained from all methods were analysed to understand the geomorphological, bathymetric and coastal dynamic changes of the study area. The results show significant and widespread deepening of bathymetry up to 1–2 m extending as far as 2 km offshore from the river outlet initiated after the collapse of the sand spit barrier. Further, the study shows separation from the mainland and buckling of the sand barrier was initiated by anthropogenic activity coupled with the release of riverine floodwater and strong waves during southwest monsoon season. The weakened and buckled sand spit barrier was migrated and welded to the mainland during calm weather of northeast monsoon. This has resulted complete change of coastal dynamics in the Kalu Ganga (River) outlet area. Since the sediment dynamics and hydrodynamics completely changed, even after 2 years, the sand spit barrier across the river outlet has not been recreated naturally. Therefore, important structures in Kalutara coastal area were threatened due to severe erosion. This study shows understanding such coastal morpho-dynamic and hydrodynamic changes are vital to implement proper coastal prevention management strategies.
Similar content being viewed by others
Availability of data and material
Not applicable.
Code availability
Not applicable.
References
Allard J, Bertin X, Chaumillon E, Pouget F (2008) Sand spit rhythmic development: a potential record of wave climate variations? Arçay Spit, western coast of France. Mar Geol 253:107–131
Amalan K, Ratnayake AS, Ratnayake NP, Weththasinghe SM, Dushyantha N, Lakmali N, Premasiri R (2018) Influence of nearshore sediment dynamics on the distribution of heavy mineral placer deposits in Sri Lanka. Environ Earth Sci 77:737
Ampitiyawatta A, Guo S (2009) Precipitation trends in the Kalu Ganga basin in Sri Lanka. J Agric Sci 04:10–18
Armaitiene A, Boldyrev VL, Povilanskas R, Taminskas J (2007) Integrated shoreline management and tourism development on the cross-border World Heritage Site: a case study from the Curonian spit (Lithuania/Russia). J Coast Conserv 11:13–22
Ciavola P (1997) Coastal dynamics and impact of coastal protection works on the Spurn Heaad spit (UK). CATENA 30:369–389
Davis RA Jr, Fitzgerald DM (2004) Beaches and coasts. Blackwell, Oxford, p 419
Duong TM, Ranasinghe R, Luijendijk A, Walstra D, Roelvink D (2017) Assessing climate change impacts on the stability of small tidal inlets: part 1—data poor environments. Mar Geol. https://doi.org/10.1016/j.margeo.2017.05.008
Duong TM, Ranasinghe R, Thatcherd M, Mahanamae S, Wang ZB, Dissanayake PK, Hemerh M, Luijendijk A, Bamunawala J, Roelvink D, Walstra D (2018) Assessing climate change impacts on the stability of small tidal inlets: part 2—data rich environments. Mar Geol 395:65–81. https://doi.org/10.1016/j.margeo.2017.09.007
Hereher ME (2015) Assessment of Egypt’s Red Sea coastal sensitivity to climate change. Environ Earth Sci 74(4):2831–2843
Holthuijsen LH, Booij N, Ris RC (1993) A spectral wave model for the coastal zone. In: Proceedings of the 2nd international symposium on ocean wave measurement and analysis, New Orleans, pp 630–641
Honeycutt MG, Krantz DE (2003) Influence of the geological framework on spatial variability in long-term shoreline change, Cape Henlopen to Rehoboth Beach, Delaware. J Coast Res 38:147–167
Hu K, Ding P, Wang Z, Yang S (2009) A 2D/3D hydrodynamic and sediment transport model for the Yangtze. J Mar Syst 77(1–2):114–136
Kanchanamala DPHM, Herath HMHK, Nandalal KDW (2016) Impact of catchment scale on rainfall runoff modeling: Kalu Ganga River impact of catchment scale on rainfall runoff modeling: Kalu Ganga River catchment upto Ratnapura. J Inst Eng Sri Lanka XLIX:1–7
King CAM (1970) Changes in the spit at Gibraltar Point, Lincolnshire, 1951 to 1969. East Midlands Geol Soc 5:19–30
Lesser GR, Roelvink JA, Van Kester JATM, Stelling GS (2004) Development and validation of a three-dimensional morphological model. Coast Eng 51:883–915
Lorenzo F, Alonso A, Pagès JL (2007) Erosion and accretion of beach and spit systems in Northwest Spain: a response to human activity. J Coast Res 23(4):834–845
Meyer BK, Vance RK, Bishop GA, Dai D (2016) Shoreline dynamics and environmental change under the modern marine transgression: St. Catherines Island, Georgia, USA. Environ Earth Sci 75(1):36
Morton RA, Speed FM (1998) Evaluation of shorelines and legal boundaries controlled by water levels on sandy beaches. J Coast Res 14(4):1373–1384
Murthy MVR, Pari Y (2009) Application of wave transformation models for estimation of morphological changes at Vellar estuary, southeast coast of India. Nat Hazards 49:371–385
Ollerhead J, Davidson-Arnott RGD (1995) The evolution of Buctouch Spit, New Brunswick, Canada. Mar Geol 124:215–236
Pajak MJ, Leatherman SP (2002) The high-water line as shoreline indicator. J Coast Res 18(2):329–337
Palamakumbure L, Ratnayake AS, Premasiri HMR, Ratnayake NP, Katupotha J, Dushyantha N, Weththasinghe S, Weerakoon WAP (2020) Sea-level inundation and risk assessment along the south and southwest coasts of Sri Lanka. Geoenviron Disasters 7:17. https://doi.org/10.1186/s40677-020-00154-y
Park JY, Wells JT (2007) Spit growth and downdrift erosion: results of longshore transport modelling and morphologic analysis at the Cape Lookout cuspate foreland. J Coast Res 23(3):553–568
Pinet PR (2009) Invitation to oceanography. Johns and Barriertlett, Massachusetts
Ratnayake NP, Silva KBA, Kumara IGIK (2013) Chloride contamination in construction aggregates due to periodic saline water intrusion: a case study in the Kaluganga River Estuary, Sri Lanka. Environ Earth Sci 69(8):2529–2540
Ratnayake NP, Ratnayake AS, Keegle PV, Mallawa Arachchi MAKM, Premasiri HMR (2018a) An analysis of beach profile changes subsequent to the Colombo Harbor Expansion Project, Sri Lanka. Environ Earth Sci 77:24. https://doi.org/10.1007/s12665-018-7234-8
Ratnayake AS, Ratnayake NP, Sampei Y, Vijitha AVP, Jayamali SD (2018b) Seasonal and tidal influence for water quality changes in coastal Bolgoda Lake system, Sri Lanka. J Coast Conserv 22:1191–1199
Ratnayake NP, Ratnayake AS, Azoor RM, Weththasinghe SM, Seneviratne IDJ, Senarathne N, Premasiri R, Dushyantha N (2019) Performance analysis of the beach nourishment and breakwater construction to control the coastal erosion at Uswetakeiyawa, Sri Lanka. SN Appl Sci 1:52
Schwartz ML (1982) The encyclopedia of beaches and coastal environments. Hutchinson Ross Publishing Cooperation, Stroudsburg, p 960
Selvan SC, Kankara RS, Prabhu K, Rajan B (2019) Shoreline change along Kerala, south-west coast of India, using geo-spatial techniques and field measurement. Nat Hazards. https://doi.org/10.1007/s11069-019-03790-2
Skilodimou H, Stefouli M, Bathrellos G (2002) Spatio-temporal analysis of the coastline of Faliro Bay, Attica, Greece. Estud Geol Madr 58(3–4):87–93
Standards for Hydrographic Surveys (2008) IHO publication. https://www.iho.int/en/standards-and-specifications. Accessed 17 Dec 2016
Williams JJ, Esteves LS (2017) Guidance on setup, calibration, and validation of hydrodynamic, wave, and sediment models for shelf seas and estuaries. Adv Civ. https://doi.org/10.1155/2017/5251902
Zhang K, Douglas BC, Leatherman SP (2004) Global warming and coastal erosion. Clim Change 64:41–58
Acknowledgements
The authors gratefully acknowledge to Copernicus Climate Change Service, Climate Date Store for providing online access to the oceanographic datasets (ERA5), and the Department of Coast Conservation and Coastal Resource Management in Sri Lanka for providing bathymetric data used in this study. We would like to thank Dr. Thushini Mendis, Nimila Dushshantha, Dinusha Kodithuwakku, Shanaka Weththasinghe, Panchala Weerakoon, Ranjani Amarasinghe and Sadun Silva for assisting in fieldwork and office work activities.
Funding
No funding was received for conducting this study.
Author information
Authors and Affiliations
Contributions
All the authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by GPG, LR, NPR, ASR, GVIS, and RJ. The first draft of the manuscript was written by GPG, and all the authors commented on previous versions of the manuscript. All the authors read and approved the final manuscript.
Corresponding author
Ethics declarations
Conflict of interest
The authors have no conflicts of interest to declare that are relevant to the content of this article.
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
About this article
Cite this article
Gunasinghe, G.P., Ruhunage, L., Ratnayake, N.P. et al. Influence of manmade effects on geomorphology, bathymetry and coastal dynamics in a monsoon-affected river outlet in Southwest coast of Sri Lanka. Environ Earth Sci 80, 238 (2021). https://doi.org/10.1007/s12665-021-09555-0
Received:
Accepted:
Published:
DOI: https://doi.org/10.1007/s12665-021-09555-0