### Abstract

The curve number and phi (φ)-index models each provide a simple one-parameter relationship between storm-event rainfall and runoff. It is shown that the curve number and φ-index models can both be used to segregate the rainfall hyetograph into initial abstraction, retention, and runoff amounts. However, the principal advantages of the φ-index model are that both rainfall distribution and duration can be explicitly taken into account in calculating runoff, and the φ index is more physically based than the curve number. The quantitative relationship between the curve number and the φ index is presented and validated with field measurements. Knowing the relationship between the curve number and the φ index is useful in that it facilitates using the extensive database of curve numbers in the more realistic φ-index model in calculating a runoff hydrograph from a given rainfall hyetograph. It is demonstrated that conventional adjustments to curve numbers can be largely explained by variations in storm duration, which suggests that variable rainfall duration can possibly be an essential factor in accounting for deviations from the median curve number of a catchment.

Original language | English (US) |
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Journal | Water Science and Engineering |

DOIs | |

State | Accepted/In press - Jan 1 2018 |

### Fingerprint

### Keywords

- Curve number
- Infiltration
- Rainfall
- Runoff
- Storm duration
- φ index

### ASJC Scopus subject areas

- Civil and Structural Engineering
- Ocean Engineering

### Cite this

**On relationship between curve numbers and phi indices.** / Chin, David A.

Research output: Contribution to journal › Article

}

TY - JOUR

T1 - On relationship between curve numbers and phi indices

AU - Chin, David A.

PY - 2018/1/1

Y1 - 2018/1/1

N2 - The curve number and phi (φ)-index models each provide a simple one-parameter relationship between storm-event rainfall and runoff. It is shown that the curve number and φ-index models can both be used to segregate the rainfall hyetograph into initial abstraction, retention, and runoff amounts. However, the principal advantages of the φ-index model are that both rainfall distribution and duration can be explicitly taken into account in calculating runoff, and the φ index is more physically based than the curve number. The quantitative relationship between the curve number and the φ index is presented and validated with field measurements. Knowing the relationship between the curve number and the φ index is useful in that it facilitates using the extensive database of curve numbers in the more realistic φ-index model in calculating a runoff hydrograph from a given rainfall hyetograph. It is demonstrated that conventional adjustments to curve numbers can be largely explained by variations in storm duration, which suggests that variable rainfall duration can possibly be an essential factor in accounting for deviations from the median curve number of a catchment.

AB - The curve number and phi (φ)-index models each provide a simple one-parameter relationship between storm-event rainfall and runoff. It is shown that the curve number and φ-index models can both be used to segregate the rainfall hyetograph into initial abstraction, retention, and runoff amounts. However, the principal advantages of the φ-index model are that both rainfall distribution and duration can be explicitly taken into account in calculating runoff, and the φ index is more physically based than the curve number. The quantitative relationship between the curve number and the φ index is presented and validated with field measurements. Knowing the relationship between the curve number and the φ index is useful in that it facilitates using the extensive database of curve numbers in the more realistic φ-index model in calculating a runoff hydrograph from a given rainfall hyetograph. It is demonstrated that conventional adjustments to curve numbers can be largely explained by variations in storm duration, which suggests that variable rainfall duration can possibly be an essential factor in accounting for deviations from the median curve number of a catchment.

KW - Curve number

KW - Infiltration

KW - Rainfall

KW - Runoff

KW - Storm duration

KW - φ index

UR - http://www.scopus.com/inward/record.url?scp=85055106256&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85055106256&partnerID=8YFLogxK

U2 - 10.1016/j.wse.2018.09.006

DO - 10.1016/j.wse.2018.09.006

M3 - Article

AN - SCOPUS:85055106256

JO - Water Science and Engineering

JF - Water Science and Engineering

SN - 1674-2370

ER -