xEXAMPLE OF REGIONAL EROSION ASSESSMENT USING THE CHW APP
This example describes how the CHW application works.
It is primarily a first rough indication of the state of erosion in an area.
The coloured coastline line in this example is computed by a computer script using the CHW methodology and serves as an overview of the state of erosion in this area.
The two coloured lines perpendicular to the coast depict two selected sites with differing conditions.
On the left is a mostly uninhabited nature conservation area with little in the way of human intervention.
The area on the right is the city of Cienaga, which is a coastal city with 80 000 inhabitants.
The tabs should be explored from hazards to risks to measures respectively.
Erosion is depicted with a color ramp ranging from green (1, low) to red (4, high).
As can be seen in the example, both areas of interest are expected to have eroding conditions. However,
their coastal environment differs as the Cienagan coastline is a sediment plain while the area on the left is a nature conservation area.
Their environmental conditions are similar other than that - medium-exposed in terms of wave conditions and both do not receive sediment inputs.
However, their socio-economic conditions differ greatly, as can be seen in the risk & measures tabs.
Risk is not part of the original CHW methodology but was added to the application to add meaning to the erosion hazard.
By comparing the resulting hazards to a basic notion of risk (i.e. capital stock, the total value of buildings without infrastructure),
it is possible to indicate areas where erosion may be most dangerous to human values.
It also helps to establish how much may be spent on the defence of the coastline to protect these values, and thus prioritize measures.
In the example image the capital stock is depicted ranging from white(<$1 million usd) to dark blue (>$1 billion usd).
While just one parameter is used, it can be cross-checked with other variables that are not included in the application for a more holistic overview.
For coastal environments with a high erosion hazard, coastal protection may be required.
These measures are specifically suited for protection from the erosion hazard present in the coastal environment.
The measures are classified in a table in the original CHW methodology and are included in the application.
Based on the capital stock present it can be inferred that Cienaga requires measures to prevent damage to its properties while the deltaic plain can be left without intervention.
While both regions have high erosion rates, only Cienaga has significant human value invested in it according to the indication of risk.
Lastly, measures may be considered from the table of measures, but these should be applied with discetion as they may exacerbate the erosion problem.