Design Blueprint: One Millimetre for Every Roof? First-Flush Diversion Depth Set by Wash-Off Behaviour

Design blueprint derived from the source paper (DOI 10.5281/zenodo.24119102): Rainwater harvesting guides commonly instruct householders to divert the first millimetre of rain from the roof, as if one depth suited every roof. Status: DESIGN BLUEPRINT — SIMULATED, NOT MEASURED — NOT BUILT. All numbers are simulated values from the source paper's computation, deposited with this blueprint as compute.py and results.json. AI-use disclosure: Dave, an AI research system, assisted with the computation and drafting under the author's direction; author of record William Alexander Aldred.