# The Influence of Hard Protection Structures on Shoreline Evolution in Riohacha, Colombia
## 5 Conclusions  
This study analyzes the coastal evolution of the urban area of Riohacha, capital of the Department of La Guajira, Colombia, between 1987 and 2022. To assess the vulnerability of this shoreline over the next 20 years, historical coastline changes--both in beach and cliff zones--were analyzed using aerial and satellite imagery alongside GIS tools.  
The construction of a series of groins near the mouth of the Rancheria River has profoundly altered coastal dynamics, promoting sediment accumulation within the groin field while intensifying erosion in downstream cliff areas. The findings indicate a shift from an erosional to an accretional regime in the groin-affected zone, where the spaces between the 150 m long structures became completely silted in just a decade. However, this sediment retention has likely disrupted the natural sediment supply to adjacent areas, accelerating cliff erosion downstream and increasing the risk to nearby buildings.  
To estimate the extent of future coastal changes, three predictive models (incorporating uncertainty assessments) were applied: Historical Trend Analysis (HTA), Extrapolation from Historical Data (EHD), and a Kalman filter-based (KFB) model. The overlap between the uncertainty bands of different models identifies the most probable locations of the future cliff crest by 2045. In the most severe scenario, if current conditions do not change, coastal retreat could reach 86 m, which would greatly affect the local community.  
The methodology and findings presented in this study are crucial for optimizing short- and medium-term coastal management strategies, particularly in areas with significant anthropogenic interventions. These results provide essential insights for assessing potential social, environmental, and economic losses, guiding land-use planning, and informing the design of mitigation measures to address ongoing and future erosion hazards.  
Conceptualization, M.F.-H., L.I. and R.C.; Data curation, L.I.; Formal analysis, R.C.; Funding acquisition, M.F.-H. and L.I.; Investigation, M.F.-H., J.E., J.J.O. and J.I.P.-M.; Methodology, M.F.-H., J.J.O. and R.C.; Project administration, M.F.-H. and J.I.P.-M.; Resources, J.E. and J.I.P.-M.; Software, M.F.-H.; Supervision, M.F.-H. and R.C.; Validation, J.E. and J.J.O.; Visualization,  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Period** & **Years** & \
\begin{tabular}{c} **Area Change** \\ **(m\({}^{2}\))** \\ \end{tabular} &
\begin{tabular}{c} **Rate of Area Change** \\ **(m\({}^{2}\)/yr)** \\ \end{tabular} \\ \hline
2003–2006 & 3 & \(-\)7058 & \(-\)2353 \\
2006–2009 & 3 & \(-\)13,115 & \(-\)4372 \\
2009–2011 & 2 & \(-\)5635 & \(-\)2817 \\
2011–2013 & 2 & \(-\)1733 & \(-\)867 \\
2013–2014 & 1 & \(-\)5239 & \(-\)5239 \\
2014–2018 & 4 & \(-\)13,446 & \(-\)3361 \\
2018–2019 & 1 & \(-\)7758 & \(-\)7785 \\
2019–2020 & 1 & \(-\)1356 & \(-\)1356 \\
2020–2022 & 2 & \(-\)2715 & \(-\)1358 \\ \hline \hline \end{tabular}
\end{table}
Table 7: Variation of the area eroded in Zone 3.  
M.F.-H.; Writing--original draft, M.F.-H., J.J.O., C.P. and R.C. All authors have read and agreed to the published version of the manuscript.  
This research has been conducted under the competitive project titled \"Ayuda en el desarrollo tecnologico yientifico para la estimacion de los cambios morfologicos de la costa de Riohacha, Departamento de la Guajira, Colombia\", funded by the Universidad Politecnica de Madrid in the program XXIV Call for Actions to Contribute to the Sustainable Development Goals (\"XXIV Convocatoria UPM para acciones para contribuir al cumplimiento de los objetivos de desarrollo sostenible\") and cofunded by the Universidad de la Guajira.  
Not applicable.  
All relevant data used for the research described in this article are included in the article and in the following link: [[https://short.upm.es/ani3h](https://short.upm.es/ani3h)]([https://short.upm.es/ani3h](https://short.upm.es/ani3h)) (accessed on 17 July 2025).  
The authors declare no conflicts of interest.