Examples of Demographics

Followings are some examples of statistics from the dataset.

• 2,386 dams (3.1%) were completed or scheduled in 1990's and afterwards
• About 30% of dams involves high or significant hazard downstream potential
• About 40% of dams do not have an Emergency Action Plan (EAP) as required.
• For 33.8% (26,003) of dams, recreation is their primary dam purpose.
• Texas has the most dams of 6,944, and Oklahoma follows it by 4,593.

Major Data Fields

Some examples of the major data fields in the NID database are as following:

• General Info: Name, Longitude, Latitude, River, County, Ownership, Designer, Purpose, Year Completed, Federal agency involvement
• Engineering Characteristics: Dam type, Core type and position, Foundation, Dam Length, Dam Height, Structure Height
• Hydrologic Features: Hydraulic Height, NID Height, Maximum discharge, Maximum storage, Normal storage, NID storage, Surface Area, Drainage Area, Spillway width, Outlet gates, Volume of dam, Number of locks, Length of locks, Lock width
• Safety: Downstream hazard potential, Emergency Action Plan, Nearest city, Distance to nearest city, Inspection date, Inspection frequency, State regulation

GIS Data Structure

The NID GIS CD-ROM contains seven shapefiles and one huge database file. The shapefiles include states, counties, cities, major highways, major rivers, drainage, and dams. The database file contains all the information on 76,953 dam records by 60 data fields (refer to Figure 2). The attribute table from the shapefile of dams involves only minimum geographic information; therefore, a new attribute table should be developed in order to generate customized themes in ArcView.

Figure 2: US Dams and Major Rivers from NID Dataset

Tennessee River Basin

For the demonstration purpose, Tennessee River Basin, HUC Region #6, is chosen. The region 6 colored by dark green spreads out over 7 states in spite of its smallest size among 22 regions (refer to Figure 3). The region 6 is governed by Tennessee Valley Authority (TVA). The TVA manages an integrated system of dams, locks, and reservoirs in the Tennessee River watershed. Then Tennessee River includes 652 navigable miles. nThe TVA system includes 20 dams for flood control and 29 for power supply. nTVA manages 480,000 acres of recreation lakes. nTVA oversees the use of 11,000 miles of public shoreline. nTVA is America's largest public power company, with 28,502 megawatts of dependable generating capacity (refer to Figure 4).

NID Dataset Projection to Hydrologic Unit

Theme Selection

The region 6 NID dataset projection starts by identifying states where the region is located. As shown in Figure 3, region 6 is covered by seven states, Kentucky, Virginia, North Carolina, Georgia, Alabama, Mississippi, and Tennessee. Once relevant states are identified, corresponding data extraction from the original 50 states dataset is followed. ArcView provides a theme selection menu. First, a user select features he or she want to extract, representing yellow highlighted areas in Figure 5. Next, activate a shapefile for dataset selection; Dams.shp is selected in Figure 5. Open the "Select By Theme" panel, and indicate operation method such as intersect. Finally choose the shapefile where the intersection operation should be performed. 

Figure 5: Theme Selection Menu (NID Dataset before Projection)

Projection

After creating shapefiles of selected states, projection can be performed by ArcView Projection Utility. To project one to another, both coordinate system and projection system should be identified first. USGS has a metafile of 1:250:000 HUC dataset in its website. Followings are information on spatial reference and Figure 6 display parameter input during the projection procedure.

Spatial_Reference_Information: Horizontal_Coordinate_System_Definition: Planar: Map_Projection: Map_Projection_Name: Albers Conical Equal Area Albers_Conical_Equal_Area: Standard_Parallel: 29.5 Standard_Parallel: 45.5 Longitude_of_Central_Meridian: -96 Latitude_of_Projection_Origin: 23 False_Easting: 0.0 False_Northing: 0.0 Planar_Coordinate_Information: Planar_Coordinate_Encoding_Method: coordinate pair Coordinate_Representation: Abscissa_Resolution: 1.0 Ordinate_Resolution: 1.0 Planar_Distance_Units: METERS Geodetic_Model: Horizontal_Datum_Name: Unknown Ellipsoid_Name: Clarke 1866 Semi-major_Axis: 6378206.4 Denominator_of_Flattening_Ratio: 294.98

Figure 6: Projection NID Dataset to HUC Coordinate System

All the seven shapefiles- states, counties, cities, major rivers, major highways, drainage, and dams- are projected to the HUC coordinate system. Figure 7 illustrates five shapefiles, after the projection completed. Major cities, highways, and rivers are displayed on top of the projected new state shapefile. Light purple dots represent all the dams across the seven states.

Figure 7: Projection Results for the Tennessee River Basin and its Neighboring States

The final version of this project is to generate new theme for the Tennessee River Basin. The same theme selection operation needs to be performed one more time with the HUC Region #6 boundaries. Compared with Figure 7, Figure 6 includes features only in the Tennessee River basin area. The thick blue line across the basin area represents the Tennessee River. Several major highways and major cities are also displayed. Light pink dots represent dams in the HUC Region #6.

Figure 8: Final Projection and Theme Selection for the Tennessee River Basin

Building a New Attribute Table of Dam Information Database

The dam shapefile in the NID CD-ROM contains the minimum geographic information on the dams. In order to support creating new themes in ArcView, a new attribute table involving targeted data fields and records should be built. Seven states records and all the safety related data fields were selected. Once a "dbf" file is built, ArcView can create a new theme using a "Add Event Theme" menu (refer to Figure 9). This dataset is also required to be projected into HUC coordinate system. The same projection utility was used.

Figure 9: Panel of Add Event Theme

 

Examples of Data Analysis

Finally, with the projected shapefiles and the newly built dataset, we can create new themes combined with the HUC system. Figure 10 shows all the dams in the Tennessee River Basin. A total of 805 dams are located in that area. Figure 11 indicates dams built within 10 years in region 6. Dams having larger than 1,000 acre-feet normal storage is illustrated in Figure 12. It is noticeable that a relatively small number of dams are located at east area. One of the major data field in the NID dataset is about safety issue. Based on three scaled level of hazard, Figure 13 displays the high downstream hazard potential dams. 250 out of 805 dams fall into this category. All these 250 dams do not have Emergency Action Plan, as shown in Figure 14.

Figure 10: A total of 805 dams in the Tennessee River Basin, HUC Region #6
Figure 11: Dams completed later than 1990	Figure 12: Dams involving larger than 1,000 acre-feet normal storage
Figure 13: Dams involving high downstream hazard potential	Figure 14: Dams involving high downstream hazard potential and no EAP

Further Technologies

Another digital dataset involving high potentials for hydrologic analysis is DEM. Some new technologies of 3D visualization claims that DEM dataset can be fully imported for generating terrain model. This 3D visualization can present a higher intuitiveness for hydrologic analyst by allowing a realistic navigation. Among several software, snap shots from Vistapro and Genesis II are illustrated in Figure 15 and Figure 16 respectively. Virtual reality technology with 3D modeling allows researchers and developers to navigate water resource areas in a dramatic realism. This virtual navigation based on real datasets can provide more intuitiveness.

Figure 15: Vistapro Application with DEM

source: Genesis II example project Figure 16: Genesis II Application with DEM

Conclusions

This term project introduced the NID dataset and demonstrated how the dataset can be combined with USGS HUC system. By combining the dataset with HUC system,   more value can be added to water resource modeling and management field. With powerful computing machine, the whole NID dataset can be projected to HUC system in future.