The impact of watershed management on coastal morphology: A case study using an integrated approach and numerical modeling

• The impact of land use changes in a watershed on coastal morphology is examined.
• Integrated approach to correlate watershed and coast through numerical modeling.
• Link for the models calibration: sediment discharge at the watershed outlet.
• Coastal model formulation uses 3 different longshore sediment transport formulae.
• Changes in sediment yield/transport (watershed) and shoreline position (coast).

Coastal morphology evolves as the combined result of both natural- and human- induced factors that cover a wide range of spatial and temporal scales of effect. Areas in the vicinity of natural stream mouths are of special interest, as the direct connection with the upstream watershed extends the search for drivers of morphological evolution from the coastal area to the inland as well. Although the impact of changes in watersheds on the coastal sediment budget is well established, references that study concurrently the two fields and the quantification of their connection are scarce. In the present work, the impact of land-use changes in a watershed on coastal erosion is studied for a selected site in North Greece. Applications are based on an integrated approach to quantify the impact of watershed management on coastal morphology through numerical modeling. The watershed model SWAT and a shoreline evolution model developed by the authors (PELNCON-M) are used, evaluating with the latter the performance of the three longshore sediment transport rate formulae included in the model formulation. Results document the impact of crop abandonment on coastal erosion (agricultural land decrease from 23.3% to 5.1% is accompanied by the retreat of ~ 35 m in the vicinity of the stream mouth) and show the effect of sediment transport formula selection on the evolution of coastal morphology. Analysis denotes the relative importance of the parameters involved in the dynamics of watershed–coast systems, and – through the detailed description of a case study – is deemed to provide useful insights for researchers and policy-makers involved in their study.