During a post-validation review of a community-based early warning system designed for flash floods in a mountainous region, the lead implementer is assessing the system\'s effectiveness. The review indicates that while the system accurately detects flood events and disseminates warnings rapidly, community members in the lower-lying areas often report receiving warnings too late to reach higher ground before the water arrives. Analysis of recent drills shows the average time from initial warning issuance to the arrival of floodwaters in these vulnerable zones is 15 minutes. The community\'s established evacuation protocol for reaching designated safe zones requires a minimum of 20 minutes for the majority of residents in these areas. What fundamental aspect of the system\'s validation, as per ISO 22328-1:2023, is demonstrably failing to meet the required standard for effective risk reduction in this specific scenario?