Understanding Coastal Erosion

Coastal erosion is the gradual wearing away of land along the shoreline due to the action of waves, tides, currents, and rising sea levels. It is a complex natural process influenced by wind patterns, storms, geological composition, and human activities that disrupt sediment supply. Communities near the coast often track erosion rates to manage infrastructure, plan seawall placements, and conserve ecosystems like dunes and wetlands that act as natural barriers.

The central idea behind this calculator is to provide a simple model for estimating how much shoreline might recede each year. While real-world predictions require detailed surveys and hydrodynamic modeling, this tool lets you explore how varying wave energy and sea level rise contribute to erosion. It also demonstrates how limited sediment can accelerate land loss. The results serve as a rough guide for understanding long-term coastal changes, not as a replacement for professional assessment.

Key Factors Driving Erosion

Wave energy is a primary driver of erosion. Stronger waves carry more momentum, which scours sand and rock from the coast. The energy of a wave can be approximated with , where is water density, is gravitational acceleration, is wave height, and is wave period. Higher waves or longer periods yield more powerful impacts on the shore.

Sea level rise further exacerbates erosion by allowing waves to reach further inland. As the baseline water level climbs, storm surges and high tides can overtop dunes and seawalls more easily. Scientists project sea levels will continue rising for decades due to climate change, so coastal planners must account for this additional stressor. Even small increases measured in millimeters per year can compound over time, exposing cliffs and beaches to more frequent flooding and wave attack.

Role of Sediment Supply

Sediment supply is equally important in determining how quickly a coastline retreats. Rivers, longshore drift, and offshore bars normally replenish sand and gravel lost to wave action. However, dams, jetties, and dredging can starve beaches of new material, leaving them vulnerable to erosion. This calculator represents sediment availability as a value between zero and one, where zero means little to no replenishment and one indicates abundant supply. Adequate sediment can offset some of the erosive force, slowing the rate of retreat.

Using the Simplified Model

The erosion estimate produced here is based on a simplified formula. Wave energy is scaled by sea level rise and then reduced by the amount of sediment available. Mathematically, it can be expressed as:

Here, is a constant scaling factor, is wave height, is wave period, denotes sea level rise, and represents sediment availability. Though highly simplified, this expression illustrates how stronger waves and rising seas accelerate erosion, while plentiful sediment reduces it.

Interpreting Results

The calculator converts the resulting energy into an annual erosion rate, shown in meters per year. Because the formula uses normalized values, the output should be interpreted comparatively rather than literally. A higher number suggests more severe erosion under the given conditions. Real-world measurements might differ depending on shoreline geology, vegetation, and human-built defenses like seawalls or groins.

Below is a table demonstrating how different parameter combinations might affect erosion. The examples are illustrative and do not reflect any specific location:

Wave Height (m)	Sea Level Rise (mm/yr)	Sediment Supply	Approx. Erosion (m/yr)
0.5	2	0.8	0.1
1.0	4	0.5	0.4
2.0	6	0.2	1.2

Planning and Adaptation

Communities dealing with coastal erosion often employ multiple strategies to slow or manage the process. Dune restoration, beach nourishment, and carefully placed groins can help trap sand and reduce wave impact. For some regions, the cost of continuous maintenance may be high, leading planners to consider relocating infrastructure away from vulnerable areas. Understanding the factors that influence erosion rates is key to deciding which approach offers the best long-term resilience.

This calculator helps visualize how seemingly small changes in wave energy or sediment supply can dramatically alter shoreline stability. It emphasizes the importance of monitoring coastal conditions and maintaining sediment flow where possible. Although basic, the model encourages deeper investigation, especially in regions where property and ecosystems are at risk.

Limitations

Erosion is a complex phenomenon involving tides, storms, geology, vegetation, and human structures. This tool simplifies those interactions and assumes uniform conditions along a stretch of coast. It does not account for storm surges, tidal cycles, or variations in beach profile. Therefore, the results should be taken as a rough indicator, best used to compare scenarios rather than serve as definitive predictions.

If you need precise forecasts for engineering projects or zoning decisions, consult coastal engineers and geologists who can model local conditions in detail. Field measurements of wave climate, sediment composition, and historical shoreline positions provide the data needed for robust analysis. Nonetheless, this calculator offers an accessible introduction to the main drivers of erosion, helping anyone gain a better appreciation for the dynamics shaping our coasts.

Whether you manage beachside property or simply enjoy visiting the ocean, understanding erosion is vital for making informed choices about development and conservation. We hope this tool sheds light on the relationships between waves, sea level rise, and sediment supply so you can explore potential outcomes for your region.