ArcHydro – Two Components

Hydrologic Data Model Toolset

Credit – David R. Maidment University of Texas at Austin

ArcHydro – Data Model

Hydrography

Network

Channel

Drainage

HydroFeatures

Based on inventory of all features for an area

Behavioral model – trace direction of water movement across landscape

Credit – David R. Maidment University of Texas at Austin

Developed with National Hydrogrophy Dataset (NHD) in mindTools intended to be used with NHD

Integrated raster-vector database

ArcHydro – Data Model

Credit – David R. Maidment University of Texas at Austin

ArcHydro - Tools

Set of tools used to derive end-productsFlow networkHydrologically conditioned DEM

Iterative, step-by-step approach with required inputs

Raster several formats, vector utilizes geodatabase only

ArcHydro - Tools Set of tools used to

achieve end-productsFlow networkHydrologically conditioned

DEMCatchment delineation

Iterative, step-by-step approach with required inputs

Raster several formats, vector utilizes geodatabase only

Credit – David R. Maidment University of Texas at Austin

ArcHydro Pros

Semi-automated derivation of key products

Semi-supportedFreeIntegrates data from

multiple sources and of different types

Cons Semi-automated Install can be difficult User interpretation

and editing introduces subjectivity

Need to know what default settings mean

Few training resources

Hydrologic Applications

Hydrologic Modeling

Process-based - try to represent the physical processes observed in the real world

Dozens available – TOPMODEL, SWAT, HSPF, etc.

Variables - Surface runoff, evapotranspiration, etc.

Increasing GIS integration

Predict response of hydrologic systems to changing variables, i.e. precipitation

Credit – Pajaro Valley Water Management Agency

Hydrologic Modeling - Hydraulics

Model hydraulics of water flow over land and through channels

Assess peak discharge, volume estimates, runoff curve numbers, etc.

HEC-RAS Increasingly GIS-based

or integrated

Erosion AnalysesLocate sites of likely gully

and other streambank interface erosion

Terrain Analysis approach – Stream Power Index (SPI)

High SPI values indicate high potential overland flow

Quantitative, spatial, repeatable

Water StorageUtilize LiDAR to accurately

identify size, depth, and location of depressions in the landscape

Reduce Peak Flows Reduce sediment and

nutrients transported downstream

Water StorageNRCS will have tools

available in the future to better calculate

Rough calculation Perform Pit-fill Subtract original

DEM from pit-filled DEM to locate larger depressions

Multiple methods for determining volume

Floodplain Mapping/DelineationNational Flood Insurance Program Local communities regulate development

in floodplains Requires accurate floodplain maps

100 Year Flood boundaryKeep building out of 100 year inundation area

Administered by FEMA Utilizes Flood Insurance Rate Map (FIRM) Update process to digital (DFIRM)

Floodplain Mapping/Delineation

Credit – FEMA

Mimic flooding at various stages to determine land area and locations inundated

Flood Inundation Area Mapping

Needs• Highly accurate land

elevation data – LiDAR DEM

• Modeling Capabilities- Hydraulic Engineering Center–River Analysis System (HEC–RAS)

• Stream-gauge heights/peak-flow readings

Flood Inundation Area Mapping

LiDAR DEM

Hydrologic Conditioning

Calibration

Stream gauge Data

Model (HEC-RAS)

Conditioned DEM

Flood Surface Elevations

Inundation Area Map

Credit – USGS

Flood Inundation Area MappingHydrologic Conditioning - Key

Credit – USGS