Environmental Engineering Reference
In-Depth Information
ditches immediately surcharged water to the land surface and up into tiles, and pre-
vented their ability to self-scour and clean influent sediments. Owing to the very flat
gradients on the ditches and tiles, this strategy resulted in a very inexpensive way to
disable the tiles (Figure 9.13).
All soils that were to be planted were initially disked lightly to corrugate the
soil surface and then seeded using several techniques. The most efficient seeding
technique used an auger drive fertilizer spreader with two hundred foot long booms
(Figure 9.14). Using this equipment and a flowable formulation of the diversity of
harvested native seeds and carrier agents (e.g., cracked corn cobs, and sand), we
perfected a method to broadcast seed approximately one acre every forty-eight sec-
onds, allowing for the planting of one thousand acres in up to two days' time. After
being broadcast, seeded soils were rolled with a cultipacker pulled behind a tractor.
Projects such as this can benefit endangered migratory species such as the whooping
crane (
Grus americana
) (Figure 9.15).
s
Ummary
The restoration of large wetlands, particularly in highly modified riverine watershed
systems, always requires significant forethought to match the potential for hydro-
logical restoration with biological outcomes. Modifications to soils (e.g., structure,
chemistry, and organic matter) during dewatered periods, such as over the years
of agricultural use, can affect the potential for recovering native vegetation sys-
tems greatly (see chapter 5). In addition, legal and physical constraints imposed by
retained hydrological and built infrastructure (e.g., legal drainage ditches, culvert
FIGURE 9.13
Restoration of hydrology required backfilling ditches and disabling the tiles.
Immediately after this was conducted, hydrology returned to the soil's surface, establishing
saturated soils and standing water in surface topographic depressions.
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