Design Blueprint: Flood Witness Network of River and Rain Gauge Nodes

DESIGN BLUEPRINT — SIMULATED, NOT MEASURED — NOT BUILT. A build specification derived from the source paper (DOI 10.5281/zenodo.24108616) for a flood witness network: US$94 river nodes (vented pressure transducer in a stilling pipe, LoRa telemetry, solar plus battery) and US$88 rain nodes at 5 km spacing, governed by the lead-time law T_lead = D/c minus 20 minutes of system latency. The reference network for a 200 km2 catchment (11 river nodes, 6 rain nodes, 2 gateways, 500 households) costs US$1,932 upfront and US$1.35 per household per year over five years, and buys 75 minutes of lead at slope 0.003. Printed failure regime: on a 10 km2 catchment the lead time is negative (-4 minutes) — no usable river-gauge warning, people-only evacuation under a rain-based watch — and lead collapses on steep slopes at short gauge distance. Includes bill of materials, sizing and spacing rules, assembly, siting along the catchment, commissioning, maintenance, and failure modes. Sole author: William Alexander Aldred (ORCID 0009-0000-1215-577X). CC BY 4.0.