Modified NRCS-CN-TUH methods for distributed rainfall-runoff modeling

Costa, Fagner França da; Paz, Adriano Rolim da; Piccilli, Daniel Gustavo Allasia

doi:10.1590/2318-0331.241920180104

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Scientific/Technical Article • RBRH 24 • 2019 • https://doi.org/10.1590/2318-0331.241920180104 copy

Modified NRCS-CN-TUH methods for distributed rainfall-runoff modeling

Métodos NRCS-CN-HUT modificados para modelagem chuva-vazão distribuída

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

Due to the relative ease of application, the CN and the Triangular Unit Hydrograph (TUH) methods are commonly used in hydraulic facilities design. This work adapts these methods to incorporate the spatial variability of the physical characteristics of the catchment. The flow travel time (tv) is computed from the DEM and the CN and TUH methods are adapted to produce results on a pixel basis. This methodology is applied to the Cascata I catchment (Porto Alegre - RS), considering two variants: i) TUHout - tv calculated from each pixel up to the catchment outlet; ii) TUHdown - tv computed from one pixel to the immediate downstream. The proposed methodology showed potential to be used for hydrologic modeling of rainfall events in small catchments, as an alternative for providing information useful for urban drainage management, as the characterization of catchment areas with distinct behavior regarding velocities and potential for runoff generation. On the other side, the results showed an underestimation of peak discharges and time to peak. Initial abstraction losses of the CN method lower than the one originally prescribed provided more realistic results, in agreement to recent studies. There is the need for an improvement of the methodology for the characteristics of the Brazilian catchments besides the simple adaptation of the classical equations of the CN method to its distributed form.

Keywords:
Hydrological modeling; Digital terrain model; Geoprocessing

Event ID	Date	Rainfall						Flow
Event ID	Date	P_total (mm)	D_prec (hours)	T_c (hours)	I_med (mm/h)	I_max (mm/h)	P_ef (mm)	Q_{p_sup} (m³/s)	Q_{p_total} (m³/s)	T_p (hours)	C_sup	C_total
PA070279	02/07/1979	18.66	3.00	2.50	6.22	21.44	4.95	3.15	3.34	3.50	0.27	0.33
PA120279	02/12/1979	14.16	4.50	3.00	3.15	19.44	1.00	0.87	1.07	6.00	0.07	0.16
PA050479	04/05/1979	7.02	2.00	3.00	3.51	8.00	1.17	0.72	0.89	3.50	0.17	0.30
PA170479	04/17/1979	7.02	3.50	2.50	2.01	6.00	0.49	0.27	0.37	3.50	0.07	0.18
PA250879	08/25/1979	12.20	1.50	3.00	8.13	18.80	1.66	1.28	1.42	2.50	0.14	0.20
PA240979	09/24/1979	12.60	1.00	3.00	12.60	22.00	1.11	0.96	0.99	2.00	0.09	0.10
PA250979	09/25/1979	39.60	4.00	2.00	9.90	24.80	5.32	3.54	3.65	3.50	0.13	0.16
PA171179	11/17/1979	28.53	5.00	3.00	5.71	18.28	4.20	2.46	2.56	5.00	0.15	0.18
PA061279	12/06/1979	7.54	2.00	4.50	3.77	8.28	0.54	0.45	0.49	5.00	0.07	0.10
PA081279	12/08/1979	14.40	1.50	4.50	9.60	27.24	2.13	1.46	1.49	4.00	0.15	0.16
PA121279	12/12/1980	52.84	2.50	1.50	21.14	88.28	7.74	7.28	7.48	2.50	0.15	0.19
PA090180	01/09/1980	13.03	2.50	1.50	5.21	24.00	3.24	2.97	3.13	4.00	0.25	0.34
PA160280	02/16/1980	21.51	4.00	0.50	5.38	27.00	5.44	5.15	5.31	2.50	0.25	0.34
PA240280	02/24/1980	13.01	3.50	1.50	3.72	18.00	2.60	2.48	2.54	2.50	0.20	0.26
PA110380	03/11/1980	12.61	2.00	2.00	6.31	21.60	1.85	1.87	1.97	2.50	0.15	0.20
PA250380	03/25/1980	17.25	1.50	2.00	11.50	34.16	2.80	2.50	2.70	2.50	0.16	0.23
PA280580	05/28/1980	8.37	5.00	3.00	1.67	6.08	0.53	0.27	0.46	5.50	0.06	0.24
PA310580	05/31/1980	27.34	1.50	2.50	18.23	47.68	4.10	3.84	4.00	2.00	0.15	0.20
PA300680	06/30/1980	11.40	2.50	1.50	4.56	11.20	0.80	0.58	0.61	2.00	0.07	0.10
PA080780	07/08/1980	20.81	7.00	2.00	2.97	7.20	0.87	0.38	0.40	4.50	0.04	0.06
PA170880	08/17/1980	28.02	3.00	3.50	9.34	21.52	7.57	3.67	3.75	3.50	0.27	0.32
PA310880	08/31/1980	17.62	4.00	1.50	4.41	10.60	2.35	1.82	1.92	3.50	0.13	0.19
PA221180	11/22/1980	8.09	3.00	3.00	2.70	7.84	0.81	0.47	0.84	3.50	0.10	0.38
PA021280	12/02/1980	22.96	6.00	1.00	3.83	18.72	3.33	2.51	3.35	4.50	0.15	0.51

Type of land use (surface) and coating of the channels	Manning’s coefficient
Surface – vegetation	0.155
*Surface – urban area	0.024
*Channel – natural	0.033
*Channel – concrete	0.015

Land use	Soil type	AMC
Land use	Soil type	I	II	III
Vegetation	B	35	55	74
Vegetation	D	60	77	89
Urban area	B	52	71	85
Urban area	D	71	85	93

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