Flood Hazard and Mitigation Potential for Irrigation Ditches
by Craig M. dePolo, Greg M. Pohll, Rosemary W.H. Carroll, Kathryn E. Ryan, Brandon P. Rasmussen, and Paul O. Malone

Series: Open-File Report 2019-06
Format: 96 pages, color

Irrigation ditches were generally designed to carry irrigation water, a steady flow along the ditch that is taken out at distribution point gates along the way. Urbanization around irrigation ditches changes the flood risk profile by increasing the consequences of flooding, increasing the number of tunnels and pipes along a ditch at road crossings, increasing the amount of storm water that can enter a ditch, and increasing the amount of debris in a ditch. One or more of these conditions can create the potential for damaging and/or dangerous flooding.

The ditch used for this study was the Steamboat irrigation ditch. We characterized the hydrologic setting of the ditch, historical flooding, conditions of the ditch, and potential downslope consequences to understand the causes and potential impacts of flooding.

Geologic Map of the Petrified Spring Fault, Gabbs Valley Range, Mineral County, Nevada
by Andrew Hoxey, Jeffrey Lee, and Andrew Calvert

Series: Open-File Report 2020-01
Format: sheet 1 (geologic map): 34 x 49 inches, color; sheet 2 (cross sections): 33.5 x 31.5 inches, color; text: 14 pages, color
Scale: 1:24,000

Examination of 30+ year old published 1:48,000-scale geologic maps and Google Earth imagery, and field reconnaissance suggest Cenozoic volcanic-filled paleovalleys in the Gabbs Valley Range, NV (central Walker Lane) are dextrally offset by five major faults, including the Petrified Spring fault (figs. 1 and 2). New detailed geologic mapping, structural studies, and 40Ar/39Ar geochronology document offset markers across the Petrified Spring fault and form the first dataset to constrain the geometry and pre-Pleistocene slip history of the Petrified Spring fault.

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