Why might farmers, others voluntarily relinquish riparian & floodplain lands?
Incentives worked out through local Groundwater Sustainability Agencies/ Plans and/or water agencies would provide the impetus.
While riparian vegetation has erroneously been a scapegoat to blame flooding on, the detention storage it offers should receive new appreciation by those seeking to sustain groundwater and to combat seawater intrusion into coastal aquifers.
Directives to move water off the land as quickly as possible are 20th Century relics, especially in the context of Sustainable Groundwater Management, but also with respect to floodplain management.
California’s Central Valley Flood Control Board has, as of August 2017, officially progressed to a 21st Century model of allowing floods to inundate floodplains, rather than continuing the practice of building ever-higher levies to (attempt to) resist flooding (Knickmeyer 2017).
Verna especially appreciates Matt Weiser’s take on it in his Water Deeply piece, “A landmark California plan puts floodplains back in business” (Weiser 2017).
In January 2016 the State Water Board issued its “First Temporary Groundwater Storage Permit to Capture Rain Season High Flows“. This arrangement permits diversion of flood flows onto floodplain agricultural lands, providing seasonal wetlands benefitting wildlife while recharging aquifers.
Rainfall to Groundwater applauds these progressive moves, but must reiterate the missing link here is holistic recognition of the detention functions offered by riparian zones.
Not just as extra space to spread floodwaters upon for recharge, but as the sponges their living soil ecosystems offer to absorb and detain that water, slowly releasing it long after the rainy season has past – when we and ecosystems can all make better use of it.
Equally important to understand is that these detention functions operate not only on lowland floodplains, but all the way up the watershed to its headwaters.
So why do California Proposition 1 funds only support mountain meadow restoration in the Sierra Nevada, when the same principles apply to all riparian zones in all watersheds???
Doesn’t it make sense to restore riparian zones throughout the state for cumulative detention storage?
Water detained in streambanks each season has a longer period of time to contribute to groundwater recharge.
Water detained in streambanks supports the fresh groundwater bulwark against seawater intrusion.
Water detained in streambanks helps reduce flooding from storm runoff, provided that riparian zones are restored throughout the watershed.
Combined with restoration of detention functions on watershed uplands, significant flood reduction may be achieved while enhancing groundwater recharge.
Click images to enlarge
Water detained in streambanks supports late spring steelhead and salmon migration (Kondolf and colleagues 1987) reducing pressures on human water resource infrastructure to provide for ecosystem needs.
These considerations can be factored into Groundwater Sustainability Plans, evaluated and dollar values assigned to finance economic tradeoffs.
Each Groundwater Sustainability Agency must determine the value of streamside riparian zones to their groundwater bottom line and compensate riparian landowners accordingly.
Knickmeyer, Ellen. 2017. State flood protection starts giving rivers more room. August 26, 2017. Associated Press, published by Mercury News.
Knickmeyer, Ellen. 2017. Room for water means less flooding. August 26, 2017. Associated Press, published by Salinas Californian.
Kondolf, G. M., L. M. Maloney, and J. G. Williams. 1987. Effects of bank storage and well pumping on baseflow, Carmel River, Monterey County, California. Journal of Hydrology 91:351-369.
Weiser , Matt. 2017. A landmark California plan puts floodplains back in business. October 10, 2017. Water Deeply. https://www.newsdeeply.com/water/articles/2017/10/10/a-landmark-california-plan-puts-floodplains-back-in-business