Converting a NEXRAD Rainfall Map into a Flood Inundation Map by ...

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2-year, 5-year, 10-year, 25-year, 50-year, 100-year, and 500-year return period.Figure 4.53 shows three grid cell isohyetal maps for the 100 year (1%)exceedance frequency and storm durations of 6 hours, 12 hours, and 24 hours asdeveloped by Halff Associates.Figure 4.53 Digital Design Rainfall Maps for Texas (color scale values in inches)There are four options available in HEC-HMS for generating a syntheticprecipitation for each subbasin: the frequency storm, the standard project storm,the SCS hypothetical storm, and the user-specified hyetograph. The frequencystorm method uses depth-duration data usually obtained from the standardpublications mentioned above i.e., TP-40, TP-49, and Hydro-35.The frequency storm method uses statistical data to generate balancedstorms (peak intensity at midpoint) with a specific exceedance probability. Thefrequency storm method was selected for the Map2Map implementation of the180
design storm input given its possibility of direct ingestion of Depth-Durationinput data from the aforementioned publications and to be compliant with themost common engineering practices.4.2.1 The DesignStormSeries ModelFor a selected frequency storm the method requires the precipitation depthfor a series of durations starting from the duration of the maximum intensity andcontinuing up to the total storm duration. In order to obtain the depth for variousdurations, geoprocessing tasks can be used to query the collection of digitaldesign storms in raster format and extract the depth for the needed duration andfor the selected frequency. This can be done in using ArcGIS ModelBuilder byintersecting the study area with the raster of precipitation depths and employingzonal statistics to get an average precipitation depth value over the watershed.Figure 4.54 illustrates the extended Arc Hydro table used to store thecontent of this spatial query for precipitation depths of various durations. TheMEAN field contains the mean precipitation depth on the area of interestextracted with Zonal Statistics in ArcGIS. The Frequency field contains the returnperiod (100 year) and the Duration field contains the series of durations needed togenerate the synthetic storms (15 minutes, 30 minutes, 60 minutes, 2 hours, 3hours, 6 hours, 12 hours, 24 hours, 2 days, and 4 days).181
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Table of ContentsList of Figures ..
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4.1.12 The XML2GDB Script Tool ....
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Figure 3.24 Components of a Steady
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Figure 4.50 Create Flood Inundation
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Chapter 1 Introduction1.1 BACKGROUN
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for undeveloped or natural conditio
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All the previous statements favor t
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science, and engineering models as
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Different approaches have been used
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generic and self-described formats,
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externally executed from a central
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though GIS-based, the system does n
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Geographic Information Systems, Arc
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By defining the three basic functio
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containing an inventory of damage s
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Data Models in charge of storing an
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Figure 3.1 Floodplain Modeling Sche
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either with Schematic Nodes (for Su
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channel cross sections, available H
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sequential data, called pathnames,
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Figure 3.5 NEXRAD square cells (873
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geodatabase formatted with the Arc
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The CrossSection feature class in A
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geodatabase (under Arc Hydro format
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3.4.4 External Execution of HEC-RAS
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analysis. In particular, GIS has be
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3.5.3 Model-Specific ElementsA geog
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Figure 3.11 Geographic and Hydrolog
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For HEC-RAS, the connectivity is ac
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cross sections in the hydraulic mod
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Section line for a RAS cross-sectio
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from the geodatabase back into the
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Figure 3.19 Relationship Classes fo
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Figure 3.20 DSS Time Series content
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Figure 3.22 Extended Time Series Co
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Figure 3.23 Creating a Flow File fr
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etween the HEC-DSS file system and
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The more specific steps for the pos
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Chapter 4 Map2Map Components4.1 MOD
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A subset of NEXRAD time series data
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A folder location is also provided
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Figure 4.4 Radar2GDB Model Componen
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ecords. Figure 4.6 illustrates the
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Figure 4.8 Time Series Tables and R
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having different formats and that a
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Part E: Time Interval of stored dat
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execution time and for their corres
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on the steps needed to transfer the
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Len_sBTime (I): The length of the s
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52: Invalid precision exponent spec
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methods: user hyetograph, user gage
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Once the hyetograph is defined (for
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The resulting runoff hydrograph is
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Thus, the time period for the entir
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After the ZSRTS subroutine is execu
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Figure 4.12 HMSCaller Model Compone
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ased on a process handle (a program
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These simple command line statement
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To programmatically accomplish this
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to provide the hydraulic input for
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information into the extended Arc H
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The HydroJunction, used for connect
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Once the identification of flow cha
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As with the GDB2HMSDSS, the first t
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4.1.7 Time Series ExtractionOnce th
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accomplish this have been developed
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straight forward for all time stamp
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As opposed to HEC-DSS, the Arc Hydr
Page 139 and 140: Table 4.4: Variable Type Equivalenc
Page 141 and 142: ZCAT DSS subroutines) and stored in
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Page 149 and 150: 4.1.9.1 Opening the HEC-DSS fileThe
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Page 159 and 160: Figure 4.31 ProjectName Property in
Page 161 and 162: Figure 4.33 RunSteady Method in RAS
Page 163 and 164: Figure 4.34 ExportGIS Method in RAS
Page 165 and 166: data structures delivered by every
Page 167 and 168: The two most well-known models for
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Page 171 and 172: Once the water surface elevations f
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Page 175 and 176: Figure 4.42 2 Foot-Contour Lines fo
Page 177 and 178: Figure 4.43 Rosillo Creek’s terra
Page 179 and 180: standard ArcGIS tool), is used in M
Page 181 and 182: By doing this, the water surface el
Page 183 and 184: Figure 4.49 Create Flood Polygon Mo
Page 185 and 186: Int OperationThe Integer operation
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Page 189: contours (isohyetals) or by interpo
Page 193 and 194: Figure 4.55 Workflow for Extracting
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Page 199 and 200: Hydro, the HydroJunctionHasCrossSec
Page 201 and 202: involved in the transformation of r
Page 203 and 204: process model in sequence. For the
Page 205 and 206: 5.6 A TRUE SPATIAL APPROACHAutomate
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Page 211 and 212: case study. Bigger watersheds (abov
Page 213 and 214: The first step consists in installi
Page 215 and 216: 3.7 Map2Map UsageAll of the model b
Page 217 and 218: Congratulations! You have successfu
Page 219 and 220: Once the simplified version of Arc
Page 221 and 222: cells that cover your study area an
Page 223 and 224: Second, the user needs to modify th
Page 225 and 226: Appendix BMap2Map CD Content1 CD Da
Page 227 and 228: o hmsproj - contains folders with H
Page 229 and 230: Goodchild, M.F., Steyaert, L.T., an
Page 231 and 232: Olsen R. J., Beling, P. A., Lambert
Page 233 and 234: Werner, M. G. F. 2001. Impact of gr
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