Riverbed hazardous invasive vegetation

by the Grand Jury

Clothes and Arundo are not native to the riverbeds.
Clothes and Arundo are not native to the riverbeds.

Are our bridges, levies and personal property at risk? The 2015-2016 Ventura County Grand Jury noted an increasing level of vegetation growing in the Ventura and Santa Clara riverbeds. Investigation also revealed that smaller tributaries are similarly overgrown. The Grand Jury expressed concern that overgrowth could cause damage to bridges, as well as riverbank erosion, and flood plain inundation should it become uprooted and wash downstream to form a dam during heavy storms.

The Grand Jury learned that the presence of an invasive species of giant reed, Arundo donax (Arundo), is the major part of the problem. The Grand Jury conducted an investigation to determine the impact of this hazardous vegetation, the potential for infrastructure damage due to uprooted vegetation, and the actions being taken to control its growth in the Ventura County watershed areas.

The Grand Jury looked to County agencies to determine their awareness of hazardous invasive vegetation and how it affects the watershed, as well as their plans to address the issue. The Grand Jury took a two-pronged approach:

It investigated the County’s ability to remove hazardous plants and debris upstream of vital infrastructure in order to protect it from flood damage.

It investigated the County’s access to environmentally protected areas for the purpose of installing and servicing rain and water runoff measuring instruments.

There is a conflict of public interests between the need to clear hazardous vegetation to protect infrastructure and the need to preserve the natural habitat from human activities that endanger it.

Because a significant portion of the populated area of the County lies in the flood plain that borders the Santa Clara and Ventura Rivers, the Grand Jury found that it is  imperative that these critical waterways stay clear of hazardous vegetation and debris  that could form dams at bridge abutments and culverts. When high water does wash vegetation and debris downstream, it must be cleared quickly so that flooding does not result.


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