Standards & references (primary set)¶

US FHWA / HEC is selected as the primary reference. HDAT’s legacy logic is a pragmatic engineering implementation; this page documents where common standards are typically consulted for:

hydrologic methods (Rational / SCS)
culvert hydraulics (inlet/outlet control concepts, headwater ratios)
open channel flow (Manning equation, critical depth, regime)
rock riprap sizing (velocity-based stability proxies)

Hydrology (common references)¶

Rational Method: standard municipal/highway drainage design manuals (assumptions, applicability, selection of \(C\)).
SCS CN method + Unit Hydrograph: NRCS TR-55 / related SCS documentation (CN concept, abstractions, UH scaling).
IDF: NOAA Atlas style approaches (regional rainfall statistics); local authority IDF curves remain authoritative.

Culverts (common references)¶

FHWA HDS / HEC guidance for culvert hydraulics (inlet vs outlet control and energy concepts).

Open channels (common references)¶

Manning equation and open-channel design references commonly used in FHWA and standard hydraulics texts.

Notes on citation style in this site¶

This repository currently contains algorithm parity documentation rather than full copyrighted standard text. Where a standard is referenced, this site:

states the engineering concept being used
documents the implemented equation/branching logic
notes inputs/outputs needed for audit