Stormwater Management is Where it all Begins for Las Vegas

The population of Las Vegas, Nevada, is almost 630,000 people—and it the past it has almost doubled every 10 years. “Explosive growth is a fact of life that is critical to planning and protecting our community from flood hazards. It points to the challenge we face in keeping our flood hazard maps up to date and avoiding problems from drainage runoff,” says Peter Jackson, Senior Engineering Associate and CRS Coordinator for the city.

The city covers over 150 square miles of desert basin surrounded by mountains with steep, dry slopes. The sole outlet is Las Vegas Wash, which flows through the metropolitan area and empties into Lake Mead. Heavy rainfall can cause flooding and flash flooding not only on the wash but also on its tributary washes and in the streets, highways, and underpasses.

Because of its fairly unusual geographic situation and fast growth, Las Vegas’ program for addressing its flood hazards is “based almost entirely on stormwater management and related regulations,” explains Jackson. Through those techniques, it aims to

• Regulate growth in the floodplain to reduce flooding impacts;
• Confine flood zones to channels and basins and have no properties in the Special Flood Hazard Area;
• Use detention basins for flood storage and include them as recreational open space whenever possible;
• Facilitate stormwater drainage through regular drainage system maintenance.

Las Vegas had a vigorous stormwater management program before it joined the CRS. “Once we got into the CRS program, we realized that if we started documenting what we were already doing, and gave a little more attention to the stormwater activities that would get us more points, we could improve our rating,” explains Jackson. “We could further reduce our flooding while also providing bigger premium discounts for our residents.” Las Vegas improved its rating to a Class 5. “This is a huge (25%) savings on NFIP premiums for these homeowners,” he adds.

Not surprisingly, Las Vegas earns a lot of its CRS credit from this complex and extensive stormwater management effort and related maintenance of the drainage system. “We spend from $3 to $6 million every year on maintenance alone,” says Jackson.

When the valley suffered major flash floods in the mid 1980s, the Clark County Regional Flood Control District was created to coordinate flood mitigation on a regional scale. The District has taxing authority and has spent over $1.8 billion on infrastructure development for stormwater control and maintenance of these structures. It works in cooperation with the City of Las Vegas and other cities and towns in the area, guided by a region-wide master drainage plan based on fully developed watersheds.

Strong Regulations and Open Spaces

There are 694 parcels of land still in the Special Flood Hazard Area, with 367 parcels having structures on them. “That’s down from several thousand some years ago,” says Jackson. As a condition of development, the City requires a technical drainage study of every parcel in the SFHA as well as for development larger than two acres. The City also has a freeboard requirements and a stronger substantial damage threshold. The City’s network of 17 detention basins, 500 miles of storm drainage infrastructure, and application of higher regulatory standards has combined to reduce the flood risk, and that is reflected by the smaller number properties that are shown in flood zones when the areas are re-mapped.

Those higher regulatory standards also earn CRS credit for the City.

“As much as possible,” says Jackson, “we try to keep our washes and basins open to store flood water, and to provide recreational places in dry times.” The city’s CRS credit for open space preservation is a product of this strategy.

Raising Public Awareness

Las Vegas continues to receive CRS credit through the Clark County Flood Control District’s aggressive outreach programs, which in one recent year included

• Visiting 52 schools with flood program information;
• Developing a television program that illustrated some of the City’s CRS-credited activities;
• Putting up an extensive billboard campaign and;
• Holding a contest to design a mock vanity license plate that would send a flood safety message, to be used on billboards.

The public outreach program from the Clark County Flood Control District provides valley-wide coverage that benefits all communities within Clark County. “It is truly a cooperative effort,” notes Jackson. The District’s Public Outreach Program focuses on educating the public about the dangers of flash flooding and informing the community about the progress of flood control in Clark County and the quality of water that drains to Lake Mead.

A Blueprint

“The CRS helped us a lot in developing a written procedure to account for everything that we do,” Jackson concludes. “And it also gives us a better handle on what we need to do.”

“The CRS showed us how to put it all together in a comprehensive way, so that everyone benefits.”