MILESTONES OF HYDROLOGY 200 YEARS OF HYDROLOGIC THOUGHT   [080505] Antoine Chézy
NUMBER	AUTHOR	MILESTONE	COUNTRY	YEAR
01	Chezy	Developed the Chézy equation, which relates the uniform flow velocity to channel roughness, hydraulic radius, and bed slope.	France	1776
02	Lagrange	Developed the equation for the relative celerity of small waves (governed by inertia and the pressure gradient) in open-channel flow (shallow water).	France	1788
03	Dalton	Developed the Dalton formula for mass-transfer evaporation rate.	United Kingdom	1802
04	St. Venant	Formulated the equations of unsteady flow in open channels.	France	1848
05	Mulvany	Developed the concept of runoff concentration, which is the basis of the rational method to calculate peak flows for small catchments.	Ireland	1851
06	Stokes	Calculated the terminal velocity of the fall of a particle in still water, known as Stokes' law.	United Kingdom	1851
07	Darcy	Developed Darcy's law for the flow of water through porous media.	France	1856
08	Breton	First to formulate the concept of flood wave celerity.	France	1867
09	Froude	Credited with developing the Froude number, which characterizes a flow regime as subcritical, critical, or supercritical, depending on whether the mean flow velocity is smaller than, equal to, or greater than the relative celerity of small (inertia-pressure) waves.	United Kingdom	1871
10	Reynolds	Formulated the Reynolds number, the ratio of macroviscosity to microviscosity, which characterizes laminar, transitional, and turbulent flow.	United Kingdom	1883
11	Manning	Developed the Manning equation, which relates the mean flow velocity to channel roughness, hydraulic radius, and bed slope.	Ireland	1889
12	Kuichling	Credited with developing the rational formula to calculate peak flow from small catchments.	USA	1889
13	Seddon	From field observations, developed Seddon's law, which equates flood wave celerity to the slope of the discharge-stage rating divided by the stream's top width.	USA	1900
14	Green and Ampt	Developed the physically based Green-Ampt model of infiltration rate.	Australia	1911
15	Bowen	Expressed the Bowen ratio, the ratio between sensible (nonevaporative) heat and latent (evaporative) heat, in terms of climatological variables.	United Kingdom	1926
16	Pearson	Developed Pearson's (Log Pearson III) method for flood frequency analysis.	United Kingdom	1930
17	Sherman	Credited with developing the concept of unit hydrograph, a conceptual model to convert rainfall into runoff.	USA	1932
18	Horton	Formulated the Horton formula, a conceptual model for the rate of infiltration.	USA	1933
19	Snyder	Credited with developing the concept of synthetic unit hydrograph.	USA	1938
20	McCarthy	Developed the Muskingum method of flood routing.	USA	1938
21	Horton	Formulated the conceptual model of overland flow.	USA	1938
22	Kirpich	Developed a formula for time of concentration based on catchment slope and length.	USA	1940
23	Gumbel	Developed Gumbel's method for flood frequency analysis.	Germany/USA	1941
24	Vedernikov	Established the criterion for the instability of free-surface flow in terms of the Vedernikov number.	Soviet Union	1945
25	Clark	Developed the Clark unit hydrograph, which routes the unit increment of runoff (effective rainfall) first through a time-area histogram and, secondly, through a linear reservoir.	USA	1945
26	Izzard	Formulated the overland flow hydrograph based on laminar flow.	USA	1946
27	Penman	Developed the Penman formula for evaporation rate, which weighs energy-budget and mass-transfer evaporation rates into one equation.	United Kingdom	1948
28	Thornthwaite	Developed the Thornthwaite formula for potential evapotranspiration based on mean monthly temperature and latitude data.	USA	1948
29	Blaney and Criddle	Developed the Blaney-Criddle formula for consumptive use of irrigated crops.	USA	1950
30	Hayami	Pioneered the mathematical treatment of flood waves as diffusion waves, developing the concept of channel hydraulic diffusivity (Hayami's diffusivity).	Japan	1951
31	Craya	Established the criterion for the possibility of roll wave formation, based on the Seddon celerity exceeding the Lagrange celerity, i.e., the Vedernikov number being greater than one.	France/ USA	1945/ 1952
32	Budyko and Drozdov	Developed a conceptual hydroclimatological model of a coupled land surface-atmosphere system, which substantially improved the understanding of the hydrologic cycle.	Soviet Union	1953
33	Mockus	Developed the NRCS (ex-SCS) runoff curve number equation to abstract total (storm) rainfall into effective rainfall (direct runoff).	USA	1954
34	Lighthill and Whitham	Formulated the mathematical theory of kinematic waves.	United Kingdom	1955
35	Mockus	Developed the NRCS (ex-SCS) synthetic unit hydrograph.	USA	1957
36	Cooper and Rorabaugh	Formulated the theory of baseflow recession curves in terms of physically based (geometric and aquifer) parameters.	USA	1963
37	Wooding	First to calculate overland flow with an open-book schematization, the so-called "Wooding plane."	New Zealand/Australia	1965
38	Monteith	Improved the Penman method to calculate evaporation by expressing the mass-transfer component on a physical basis, leading to the Penman-Monteith method.	United Kingdom	1966
39	Woolhiser and Liggett	Developed the criterion for the applicability of kinematic waves in terms of the kinematic flow number.	USA	1967
40	Cunge	Explained the behavior of the Muskingum method in terms of the numerical diffusion of the discrete analog of the related kinematic wave equation, leading to the Muskingum-Cunge method.	France	1969
41	Dooge	Extended Hayami's diffusion analogy of flood waves to the realm of dynamic waves by expressing the hydraulic diffusivity in terms of the Froude number.	Ireland	1973
MILESTONES OF HYDROLOGY 200 YEARS OF HYDROLOGIC THOUGHT   [080131] Robert Manning

V. M. Ponce

Manning's n Pictorial

Manning's n for flood plains

Facets of Hydrology

History of the Chezy formula

History of the Manning formula

Conversation with Vic Mockus

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