Proposed Hydraulic Design Manual Updates

Proposed Hydraulic Design Manual Updates

Ab Maamar-Tayeb, P.E. Hydrology and Hydraulics Section

Short Course Hydraulics Session

OctOocbteorb1er41, 240, 2020

Agenda

Hydraulic Design Manual Updates

Chapter 4 Hydrology (Updates)

? Update to NOAA Atlas 14 rainfall data guidelines. ? Update on Rainfall Temporal Distribution based on

NRCS guidance. ? Peak Rate Factor (PRF) guidance based RTI Research. ? Statistical Analysis of Stream Gage Data based on RTI

Research.

Chapter 2 and Chapter 13 (Updates)

? Drainage Policy and Storm Water Management ? Developers Outfall Policy and Detention

Chapter 16 (New Chapter)

? 1D and 2D Unsteady Analysis

Short Course Hydraulics Session

October 14, 2020

2

Updates: Chapter 4 - Hydrology

Chapter 4 Updates:

? Four Updates Topics

? NOAA Atlas 14 ? Rainfall Distribution Guidance ? Peak Rate Factor ? Statistical Gage Analysis Generalized

Skew Update

Short Course Hydraulics Session

October 14, 2020

3

Updates: Chapter 4 - Hydrology

Chapter 4 Updates: NOAA Atlas 14

? Rainfall data updated with the publication of NOAA Atlas 14 in 2018 ? Considered best available data. ? All projects must use NOAA Atlas 14 Data.

Two Sources for NOAA Atlas 14 Data

NOAA's National Weather Service Website ? "NOAA Atlas 14 Point Precipitation Frequency Estimates" :



EBD Lookup Spreadsheet (EBDLKUP2019) completed by RTI project 0-6980 ? Provides intensities for Rational Method input (not depths)

Short Course Hydraulics Session

October 14, 2020

4

Updates: Chapter 4 ? Hydrology ? Atlas 14 Rainfall Data

Chapter 4 Updates: NOAA's National Weather Service Website ? "NOAA Atlas 14 Point Precipitation Frequency Estimates" :

Short Course Hydraulics Session

October 14, 2020

5

Updates: Chapter 4 ? Hydrology ? Atlas 14 Rainfall Data

Created e,b,d spreadsheet

? EBDLKUP-2019-vC6.2.10.xslm (replaces EBDLKUP-2015)

? New e, b, d coefficients determined for intensity, duration, frequency (IDF) curves

? Allows for partial duration or annual maximum series.

? Developed sub-county rainfall zones due to rainfall variation across some counties. 500 zones total based on spatial error of 20, 15 and 10 percent

? Includes KMZ google earth map file

Compiled new IDF curves in library

? Library integrated with Bentley OpenRoads Designer

Short Course Hydraulics Session

October 14, 2020

6

Updates: Chapter 4 ? Hydrology ? Rainfall Distribution

? Rainfall temporal distribution

? NRCS states Type II-III storms out of date ? NRCS Type II-III storms not included in

HEC-HMS 4.3 ? New recommended method: Balanced

Storm Methods (Frequency storm ? HECHMS) ? Storm Peak at 67 percent of Duration

Short Course Hydraulics Session

October 14, 2020

7

Updates: Chapter 4 ? Hydrology ? Peak Rate Factor

Peak Rate Factor (PRF) guidance

? Peak Rate Factor is parameter that defines the shape of the hydrograph

? Suggests consideration of PRF values other than the default value of 484 ? Possible range: 100-600

? PRF selection will be based on slope and basin area.

? RTI Research Project 7010

Short Course Hydraulics Session

October 14, 2020

8

 ................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download