How Do the Percentages Work in LDC and HDC Alerts?

What are LDC and HDC?

LDC (Lowest Daily Clearance) is the minimum level at which navigation is safe, and HDC (Highest Daily Clearance) is the maximum safe level. If the water level falls below LDC or rises above HDC, navigation becomes dangerous. Alerts based on LDC and HDC are sent depending on the percentage at which the water approaches these critical values.

What Do the Percentages Mean for LDC and HDC Alerts?

The alert system is based on the percentage of the LDC and HDC values at which the water approaches these limits. Users can set percentage thresholds that trigger alerts when the water approaches a critical value.

For example, if a user sets a threshold of 80% for LDC, they will receive an alert when the water level drops to 80% of the LDC value. Similarly, for HDC, if the threshold is set at 80%, an alert will be triggered when the water rises to 80% of HDC.

How Are the Percentages for LDC and HDC Calculated?

Calculating the percentages for LDC and HDC alerts is fairly simple. The formula is:

Percentage LDC = (Current water level / LDC) * 100
Percentage HDC = (Current water level / HDC) * 100

Here is a detailed example:

• Percentage LDC: If the current water level is 400 cm and LDC is 500 cm, then Percentage LDC = (400 / 500) * 100 = 80%. This means the water level has dropped to 80% of LDC, and if the alert threshold is set to 80%, an alert will be sent.
• Percentage HDC: If the water level is 950 cm and HDC is 1000 cm, then Percentage HDC = (950 / 1000) * 100 = 95%. This indicates that the water level has risen to 95% of HDC, triggering an alert if the threshold is set at 95%.

Using Percentages in Custom Alerts

In the Danube Alert app, users can set custom percentage thresholds to receive alerts when the water level approaches LDC or HDC. For example, if a user sets thresholds of 85% for LDC and 90% for HDC, they will receive notifications when the water drops to 85% of LDC or rises to 90% of HDC.

These alerts help users to be proactive and continuously monitor the water level, thus preventing dangerous incidents or economic losses caused by floods or unsafe navigation.

Examples of Calculations for LDC and HDC Based on Percentages

Let’s perform calculations for a current water level of 500 cm, an LDC of 50 cm, and an HDC of 600 cm. We will analyze percentages from 10% to 90%.

Calculation for LDC

Formula: Percentage LDC = (Current water level / LDC) * 100

• 10% LDC: (500 / 50) * 100 = 1000%. The current level is far above 10% of LDC, so no alert is sent.
• 20% LDC: (500 / 50) * 100 = 1000%. The current level is above 20% of LDC, so no alert is sent.
• 30% LDC: (500 / 50) * 100 = 1000%. The level is above 30%, no alert is sent.
• 40% LDC: (500 / 50) * 100 = 1000%. Still above 40%, no alert is sent.
• 50% LDC: (500 / 50) * 100 = 1000%. The level is above half of LDC, so no alert is sent.
• 60% LDC: (500 / 50) * 100 = 1000%. No alert is sent, as the current level exceeds 60% of LDC.
• 70% LDC: (500 / 50) * 100 = 1000%. The level is above 70%, no alert is sent.
• 80% LDC: (500 / 50) * 100 = 1000%. No alert is sent because the water level is too high.
• 90% LDC: (500 / 50) * 100 = 1000%. No alert is sent because the water is above 90% of LDC.

Calculation for HDC

Formula: Percentage HDC = (Current water level / HDC) * 100

• 10% HDC: (500 / 600) * 100 = 83.33%. The current level is above 10% of HDC, so an alert is sent if the threshold is 10%.
• 20% HDC: (500 / 600) * 100 = 83.33%. The water level is above 20%, so an alert is sent.
• 30% HDC: (500 / 600) * 100 = 83.33%. The water exceeds 30% of HDC, triggering an alert.
• 40% HDC: (500 / 600) * 100 = 83.33%. An alert is sent at this level.
• 50% HDC: (500 / 600) * 100 = 83.33%. The water level is above 50%, so an alert is sent.
• 60% HDC: (500 / 600) * 100 = 83.33%. Alerts are triggered because the water exceeds this threshold.
• 70% HDC: (500 / 600) * 100 = 83.33%. The water has passed 70%, so an alert is sent.
• 80% HDC: (500 / 600) * 100 = 83.33%. The 80% threshold is reached and an alert is sent.
• 90% HDC: (500 / 600) * 100 = 83.33%. The water is between 80% and 90%, so an alert is sent.

In conclusion, the current water level is high enough to trigger HDC alerts set between 10% and 90%. If the threshold is set at 83% or lower, an alert will be sent.

When Will NO Alerts Be Sent?

There are cases when alerts will not be sent, namely:

• For LDC: If the current water level is much higher than the LDC (e.g. 500 cm vs 50 cm), no alert will be sent regardless of the percentage.
• For HDC: If the set percentage is higher than the current water level percentage (for example, 90% or higher), no alert will be sent. In our example, the water level is 83.33%, so if the threshold is set at 90%, no alert is triggered.

In conclusion, alerts will not be sent if the water level does not reach the percentage threshold set by the user. This flexibility helps prevent false or excessive alerts.