Impacts to Sizing of Conservation Practices in Pennsylvania from Implementation of NOAA14 Rainfall Data

Geoffrey A Cerrelli
2008 2008 Providence, Rhode Island, June 29 - July 2, 2008   unpublished
Since its release in May 1960, the USDA-Natural Resources Conservation Service (NRCS) has used the National Weather Service Technical Paper No. 40 (TP-40) as the primary reference to establish design rainfall volumes for various frequency storms. The standard NRCS Type II design rainfall distribution is most widely used across the USA. Developed using the TP-40 data, it is coupled with the rainfall volumes and is used with predictive hydrology models to size conservation practices for
more » ... tices for agricultural applications. The National Weather Service has recently updated TP-40 with newer and more comprehensive data in the form of NOAA Atlas 14 for select portions of the U.S., including Pennsylvania (PA). This produces new design storm volumes and distributions (per frequency). Various counties in PA have been analyzed to determine the typical magnitude of change (if any) to predicted design peak discharge rates and related impact to sizing of agricultural conservation practices when switching from TP-40/Type II distribution to NOAA Atlas 14 rainfall volume/distribution. The primary focus is on surface water conveyance practices such as diversions and waterways. The NRCS runoff estimation method and grassed waterway design procedure (NRCS Engineering Field Handbook), PA conservation practice design standards (NRCS Field Office Technical Guide, Section IV), and NRCS Win TR20 hydrology model serve as the basis for evaluation of design peak discharge and hydraulic capacity of the practices.
doi:10.13031/2013.24583 fatcat:j65g2f3il5caxlogt7yfl2toki