Solid Terrain Modeling Plays Key Role in Award-Winning Navajo Housing Authority Floodplain Project


The Navajo Housing Authority (NHA) needed a way to efficiently plan for the construction of homes on its 27,000 square mile territory while mitrigating the cotsts of home and property damage due to flooding. To achieve this goal, NHA partnered with three different companies that provided state-of-the-art satellite imaging, database, and terrain modeling technologies to conduct an innovative floodplain mapping project. The results of this project will help NHA minimize flood risk to existing homes and infrastructure, fulfill HUD requirements, and protect lives and property in the future.


The Navajo Housing Authority (NHA) has been collecting housing and land management data since its inception in 1963. In November 2007, Survey Manager Michael Paisano and Realty Manager Dwayne Waseta developed a plan entitled “Land & Geographic Information Management System,” which envisioned a multi-phased plan and system. The first phase involved creation of a “Project Needs and Project Requirements” document that identified the approach, system architecture, budget, and schedule for the implementation of a Navajo Housing Authority (NHA) land information system. However, the project stalled shortly thereafter.

In July 2010, Nadine Clah was hired as the GIS Coordinator for NHA and tasked with finishing the vision that Paisano and Waseta began in 2007. She brought with her 14 years of GIS and IT experience from the Gila River Indian Community in Sacaton, Arizona, where she assisted public safety departments with the development of a nested-grid addressing scheme used in the Enhanced 911 system. This addressing scheme was the first of its kind to locate calls in the U.S

The primary goal with NHA’s Land Information System project is to conduct the business of planning and building homes more efficiently. To help achieve this goal, the NHA embarked on a massive project to map the floodplain of the entire Navajo Nation, with particular emphasis on the subdivisions and homes maintained by the NHA. Implementing this project required partnering with companies who could provide expertise in the following areas:

  • Developing a Esri© ArcGIS online application to improve data management
  • Conducting aerial photography and digital imaging of the floodplain area
  • Developing geospatially accurate 3D terrain models to visually communicate the data

Phase 1 of the project ran from August 2011 to March 2012. Phase 2 began in August 2012 and will end in November 2013. Phase 3 will commence at some unspecified future date.

Developing the Esri© ArcGIS Application

NHA hired URS Corporation, a leading provider of engineering, construction and technical services, to conduct the floodplain mapping and analysis part of the project. To facilitate the data analysis process, URS developed an Esri© ArcGIS online application that allows NHA to more effectively create, store, and distribute land and housing records, including the ability to overlay the data and perform analysis for planning purposes. This server-based application also enables NHA to relay project information, share documents, monitor project status, and make more informed decisions in planning and building homes.

With the Esri© ArcGIS online application, NHA can:

  • Improve data quality, accessibility and sharing of land records
  • Maintain controls for dispersing land information
  • Build and maintain a base map framework that can be used for multiple purposes
  • Build and maintain a framework that supports parcel-level activity
  • Maintain security and confidentiality where required
  • Minimize costs, reduce duplication, and increase efficiency
  • Make land information readily available to users

Conducting the Aerial Mapping

To conduct the aerial mapping and digital imaging for the project, NHA partnered with AeroMetric, a full-service geospatial solutions company. The data captured during the aerial mapping, which includes detailed digital elevation data and four-band orthoimagery, was used to create a comprehensive digital land base for the GIS database developed by URS.

The Navajo Nation’s vast size and rugged terrain presented multiple challenges for the AeroMetric team. To solve them, AeroMetric developed an innovative solution based on a custom map projection – created specifically for the NHA – that set 73 control monuments across the rugged 19.2 million-acre area. AeroMetric also utilized five systematically coordinated aircraft to cover the project area in record time.

The high level of accuracy required for the digital elevation model and tone matching prompted the firm’s technical staff to develop an innovative process utilizing best-in-class tools and systematic quality control. For their outstanding work on this project, AeroMetric received a MAPPS Geospatial Services Excellence Grand Award.

Creating the 3D Terrain Models

To create the 3D models that serve as educational tools for the project, NHA enlisted the services of Solid Terrain Modeling (STM), leading producer of geospatially accurate, three-dimensional terrain models. Using the imagery captured by AeroMetric, STM created 6’ x 8’ 3D terrain models of the entire Navajo land area. By physically simulating the characteristics of the Navajo land formations, these models show NHA and Navajo Council members exact land features and associated hazards that potentially affect the Navajo People. This visual interpretation of their data communicates the importance of the NHA’s ongoing project, giving everyone a better understanding of how to use the nation’s resources more effectively.

According to Clah, more than half of the land in the Navajo Nation is not suitable for building. The solid terrain models provide a precise picture of the entire Navajo Nation. This helps tribal council members, planners and developers visually understand what the land looks like and where the Navajo Nation can feasibly build homes and other infrastructure.

NHA Floodplain Mapping Project Results

To date, more than 3,000 miles of floodplain have been delineated. In August, URS will begin mapping the 1% chance floodplain – areas that flood only once every hundred years with exceptionally devastating consequences. The 100-year flood is referred to as the 1% annual exceedance probability flood, since it is a flood that has a 1% chance of being equaled or exceeded in any single year.

When the project is complete it will include:

  • The full 100-year flood plain mapping, with a depth grid indicating flood plain boundaries and depth of the water
  • Fire mapping, using terrain data of slope and vegetation layer (fuel load) to determine high-risk fire areas
  • Feature extraction and a routing system to identify all housing areas and the quickest routes to get there

In addition, the GIS system is being built with the capability of adding more layers, such as environmental and planometric data. This will enable the NHA to track home information down to the individual parcel level, including the homeowner’s name, when the home was built, what type of utilities it has, and other information pertinent to a housing authority.

As a result of this project, NHA can use all their land management data sets in a more informed way, enabling them to become better planners and build more resilient and sustainable communities.

“Solid Terrain Modeling showcased the true characteristics of our unique land features, giving members of our communities a physical representation of what our territory actually looks like.” -– Dwayne Waseta, Division Director, Development & Construction Services Division


Press Release – Technology Meets Tradition in NHA Floodplain Project