Details:

Creators:
Olson, Scott A.
Corporate Creators:
Geological Survey (U.S.)
Corporate Contributors:
United States. Federal Highway Administration
Subject/TRT Terms:
[+]
Bridge Design Data Collection Design Flood Design Storm Floods--New Hampshire Geographic Information Systems Mathematical Prediction Peak Discharge Regression Analysis Scour Scour At Bridges Streamflow Streamflow--New Hampshire--Mathematical Models Stream Gages
Publication/ Report Number:
FHWA-NH-RD-14282F
Resource Type:
Tech Report
Geographical Coverage:
New Hampshire
Edition:
Final report.
Corporate Publisher:
New Hampshire Department of Transportation
Abstract:
This report provides estimates of flood discharges at selected recurrence intervals for streamgages in and adjacent to New Hampshire and equations for estimating flood discharges at recurrence intervals of 2-, 5-, 10-, 25-, 50-, 100-, and 500-years for ungaged, unregulated, rural streams in New Hampshire. The equations were developed using generalized least-squares regression. Flood-frequency and drainage-basin characteristics from 117 streamgages were used in developing the equations. The drainage-basin characteristics used as explanatory variables in the regression equations include drainage area, mean April precipitation, percentage of wetland area, and main channel slope. The average standard error of prediction for estimating the 2-, 5-, 10-, 25-, 50-, 100-, and 500-year recurrence interval flood discharges with these equations are 30.0, 30.8, 32.0, 34.2, 36.0, 38.1, and 43.4 percent, respectively.

Flood discharges at selected recurrence intervals for selected streamgages were computed following the guidelines in Bulletin 17B of the U.S. Interagency Advisory Committee on Water Data. To determine the flood-discharge exceedence probabilities at streamgages in New Hampshire, a new generalized skew coefficient map covering the State was developed. The standard error of the data on the new map is 0.298. To improve estimates of flood discharges at selected recurrence intervals for 20 streamgages with short-term records (10 to 15 years), record extension using the two-station comparison technique was applied. The two-station comparison method uses data from a streamgage with long-term record to adjust the frequency characteristics at a streamgage with a short-term record.

A technique for adjusting a flood-discharge frequency curve computed from a streamgage record with results from the regression equations is described in this report. Also, a technique is described for estimating flood discharge at a selected recurrence interval for an ungaged site upstream or downstream from a streamgage using a drainage-area adjustment.

The final regression equations and the flood-discharge frequency data used in this study will be available in StreamStats. StreamStats is a World Wide Web application providing automated regression-equation solutions for user-selected sites on streams.


Format:
PDF
Funding:
14282F, X-A000 (601)
Collection(s):
US Transportation Collection
Main Document Checksum:
[+]
urn:sha256:3865e9a7155f28fc5203215479639bacc055b072703dbd37705cf3fefa0898af
Download URL:
https://rosap.ntl.bts.gov/view/dot/25195/dot_25195_DS1.pdf
File Type:

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