Daily Sun Gardening Etcetera 4/30/11

LANDSCAPING FOR FLOODING
Cindy Murray

As summer approaches, many of us who live in the environs northeast of Flagstaff turn an anxious eye to the charred slopes of the San Francisco Peaks and ask ourselves, “What does the monsoon have in store for us this summer?” Will a massive cloudburst send a forty-five minute deluge onto the burned slopes resulting in a mud and debris flow into neighborhoods for miles around, as occurred one afternoon last July? Will a series of El Nino storms bombard the region throughout the summer causing even more flooding, as they did last summer? Or will it be a mild monsoon with sporadic and gentle rains?
Of course, not even the experts have answers to all of these questions. We must be remain vigilant and not get complacent. On the other hand, we don’t want the threat of flooding to rule our lives. Some of us would like to relandscape.
As I’ve driven through the flood zone over the past several weeks, I’ve noticed that many residents are not only landscaping, they’re adding a measure of flood prevention in the process. Several of my neighbors in Hutchison Acres are putting up walls to hold back future floodwaters. I must admit that when I first heard about this, I envisioned unsightly cinderblock walls such as the ones that stretch for miles in suburbia. But, to my delight, the walls being built in my neighborhood are both attractive and designed to complement the architecture and color scheme of the homes.
Nadine Barlow hired Warners (a local nursery and landscaping business) to erect a gray serpentine Rockwood retaining wall. It’s constructed of one-square-foot modular masonry units that are stacked four units high (one of the units is underground, serving as a footing). Several malpais boulders are tastefully interspersed within the wall to give it a rustic charm. A swale (shallow trough) will catch the diverted water and carry it to the rear of the property. It’s illegal to direct water onto someone else’s property.
Frank and Berni Koenen built a gracefully arcing wall along the front and sides of their corner property. Its brick red color pairs nicely with the trim on the home. Bernie explains that the wall is comprised of interlocking gravity blocks, which they purchased from Borders Construction. Since each hollow block weighs ninety pounds, the sheer weight of the wall should be all that’s needed to hold back floodwaters.
Don and Jeanne Crawford consulted a hydrologist before hiring Mario’s Creations to build a handsome pair of low retaining walls composed of gray and burnt umber malpais rock. Trudy Sanchez, of Mario’s, says the backfill areas will eventually be planted with various perennials and shrubs such as gaillardia, Shasta daisies, lilacs, and junipers.
Many residents are mounting berms, but it is vital that they are stabilized with vegetation. Jennifer Temkin, a botanist at Flagstaff Native Plant and Seed advises, “Start with native grasses. They grow fast and have lots of roots that hold the soil together. Switchgrass is a great soil stabilizer because it spreads by rhizomes and can take some flooding. Western and Nebraska sedge, which are related to grass, tolerate soggy soil and drought.” Little bluestem, and sideoats grama also work well for revegetation. Native shrubs and vines that withstand wet and dry cycles include: currant, blue elderberry, chokecherry, western virgin bower, hops, redtwig dogwood, and wild grape.
Not everyone, however, has the desire or means to build walls or berms. My husband and I are leaving our sandbags in place for now, but I’ll conceal them by planting moderately tall native perennials such as skyrocket, globemallow, goldenrod, yarrow, and Arizona penstemon. Additionally, we’ll stabilize our recently widened ditches with western sedge, asters, fleabane, gaillardia, and sunflowers. These will also serve to slow down potential floodwaters. We’ll remove invasive species including cheatgrass, diffuse knapweed, and Dalmation toadflax.
The Greek philosopher, Plato, stated that necessity is the mother of invention. I hope this article will encourage members of my community to use their mettle and ingenuity to design and implement landscaping that will not only be appealing, but will also afford peace of mind.
Cindy Murray, a biologist and substitute elementary teacher, is a Master Gardener. Dana Prom Smith (http://highcountrygardener.blogspot.com), editor of GARDENING ETCETERA, can be reached at stpauls@npgcable.com.