USA - Hard rain could create severe flooding downstream from orchards
While there has been extensive ripping of foothill soils several feet deep to allow planting of nut trees, there has been little discussion of the effects on storm runoff from those soils. There are potential pluses and problems. First, the pluses: Ripped soils become more permeable to rainfall penetration and root growth, so light to moderate rainfall infiltrates rather than runs off. That contributes to soil moisture storage and perhaps some very small contribution to groundwater storage, in an area of generally little rainfall. There has been no really hard and prolonged rainfall since the extensive ripping has been done in the foothills of Stanislaus County, so everything seems fine so far. About the problems: Occasionally, prolonged and hard rains have created problems in the past. When such rains occur in the future, there is a potential of overcoming the infiltration capacity of those ripped and now highly erodible soils in hillside orchards. Then overland water flow can cut into the erodible soils and transport large amounts of that soil into stream channels. In turn, that can cause much more runoff than has occurred in the past. Until that happens, everyone politically and economically benefiting from the present situation will say there is no problem. With thousands of hillside acres in our region having been ripped and planted in tree crops, there is no prior precedent anywhere in the country. The odds of such heavy rainfalls are impossible to predict, though the amount of moisture in the atmosphere has been increasing for decades due to ocean warming. That is thought to perhaps account for the unusual strength of storms elsewhere in the country. Some people have noted that grass and weed roots will prevent ripped soils from eroding, but they do not understand that normal settling and compaction due to moderate rainfall will not replicate the compaction prior to ripping. Others note that many farmers have installed barriers to sediment runoff. I doubt such barriers will help much in the event of a truly massive erosion event. If large amounts of sediments enter the streams, due to erosion of ripped soils, the farmers who haven’t even tried to reduce erosion might be fined. Many will have their profits to balance that cost. But homeowners living near areas susceptible to flooding will have nothing to help them unless they’ve bought flood insurance. We will know if my concerns are valid only when we have prolonged and intense rainfall. When that might occur is anyone’s guess; it didn’t occur last year. The main reason I am writing is to encourage homeowners in flood-prone areas to consider buying flood insurance. Insurance rates should be relatively low because insurance companies depend on past experience until shown otherwise. I know of no situation remotely similar to this. Perhaps it’s better to have insurance and not need it than to suffer a flood and realize you’ve lost a great deal. Source - http://www.modbee.com
