Occupying a 12-mile stretch of land in the southeast portion of the Las Vegas Valley, the wash averages 153 million gallons of daily water flow and is the primary drainage channel for all stormwater, urban runoff, shallow groundwater, and highly treated effluent. Wetlands serve as a polishing mechanism as flows move through the wash, under Lake Las Vegas, and to Lake Mead and the Colorado River system. Lake Mead, the largest man-made reservoir by volume and a designated U.S. national monument, provides approximately 85 percent of the water supply for valley residents and some 12 million people living in Arizona and California.

The wash supports diverse plant and animal species and at one time contained about 2,000 acres of wetlands. In the past 30 years, that number has diminished to 300, a byproduct of increased flows in the wash resulting from rapid population growth.

Fortunately, Leica Geosystems' ERDAS IMAGINE software and Esri's GIS software have provided an enterprisewide solution that serves many private citizens; Businesses; universities; and local, state, and federal agencies cooperating to protect and manage the wash.

LVWCC's GIS/remote sensing staff forms the epicenter of all wash activities. The staff manages and coordinates all types of data, initially centralized in ArcInfo and now in ArcGIS 8.1, to support various study teams as they identify issues and develop specific recommendations for the wash. The database is routinely updated with aerial photos processed with ERDAS IMAGINE software, and Web sites are maintained to facilitate access and data sharing between study team members, other agencies, and the public.

According to Kim Zikmund, LVWCC's project manager, the committee's framework "allowed people to consider all of the issues at the same time." The first recommendations were rolled into a comprehensive plan made available online (www.lvwash.org/html/being_done_index.html). "We have very aggressive plans to enhance and stabilize the wash," says Zikmund. "The comprehensive plan provides specific, on-the-ground recommendations that we can act upon, thereby providing for the long-term management of the wash."

Aerial photos dating back to the 1930s, site photos, and project information have been indexed and registered, helping the LVWCC GIS team document temporal changes in the wash. Adding one-foot resolution digital aerial photos collected by Clark County since 1998, supplemented by low altitude high-resolution aerials LVWCC collects every six to eight weeks, helped establish baseline data coverages for monitoring progress and impacts along the wash.

"This area is undergoing rapid change," explains Ehrenberg. "Aerial photos are a great method of adding data quickly to your GIS and augmenting work in the field. We now have access to current, very detailed imagery on a regular basis." The low-resolution aerial photos are scanned at 1,000 dots per inch (dpi), yielding 3/10-pixel resolution, and at 96 dpi for thumbnails used to index each aerial photo and register it to a basemap.

New GIS and geographic imaging tools are added to match the study team's requirements and, according to Ehrenberg, they now "use just about every Esri and ERDAS product available." Currently, IMAGINE OrthoBASE is used for mosaicking and orthorectification. By mid-2002, LVWCC will upgrade to the full ERDAS Photogrammetry Suite for additional 3D GIS capabilities via elevation and 3D feature extraction tools.

Helping nontechnical people grasp the issues facing the wash is a priority for LVWCC. "Three-dimensional visualization helps us explain projects and communicate the current conditions of the area," says Zikmund. "Imagery and GIS help people understand in tangible numbers what they are seeing, which helps us all better manage our resources."

"Three-dimensional visualization is an important tool when presenting data," explains Ehrenberg. "We create 3D fly-throughs with IMAGINE VirtualGIS for showing areas of the wash. Many people don't immediately understand 2D, but in 3D the results are more dramatic and the visual impact really aids in the understanding of a problem or result."

ArcGIS 8.1 and IMAGINE Professional 8.5, along with their extensions and add-on modules, are the backbone of the GIS and the main tools for acquiring, updating, and analyzing the data. ArcView 3.2a supports many of the hydrologists, biologists, and other professional field staff and researchers with basic mapping and image analysis needs. By mid-2002, LVWCC expects to integrate ArcIMS into the existing Web sites, making maps more current and interactive, and ArcPad technology into fieldwork, making the GIS more portable. "If people can query the data in the field, it not only helps them, it also helps us by streamlining data input," says Ehrenberg. "This will save us a lot of time and greatly reduce errors in the system."

Establishing data standards is a challenge because of the various data entering the system. As data integration has become easier, evolution in software design and import capabilities also make it easier to incorporate any type of data (including CAD) much faster. "Standards will help completely automate the process, decrease errors, and increase data availability," says Ehrenberg.

Currently running on UNIX and Windows NT systems, most of the GIS data is, or will be, stored in ArcSDE coverages linked with the databases warehoused in Oracle 8.1. Since most data is queried or accessed by member agencies or the public through the Web, development of Web-based solutions is the thrust of future development initiatives.

"Accessing real-time imagery and data on the Web will enable the community at large to visualize geographic information 24 hours a day, seven days a week," says Zikmund.

For more information about the Las Vegas Wash, contact Art Ehrenberg (tel.: 702-822-3383, e-mail: art.ehrenberg@lvvwd.com, Web: www.lvwash.org). For more information about ERDAS IMAGINE, contact Leica Geosystems (tel.: 877-463-7327, Web: www.erdas.com).