The weather models continue to call for a potentially extreme El Niño event this winter in central and southern California. Being prepared for what Mother Nature has to offer is your first line of defense in protecting your assets. Names like “Godzilla El Niño” and “Bruce Lee El Niño” are commonplace and hint at the destructive power these storms can possess. Past experiences have shown us that precipitation extremes of 150 to 200% of normal are not uncommon during El Niño events and can cause potentially damaging rains and flooding.
To help you prepare, we offer up a top six list of maintenance activities to tame El Niño impacts to your property and avoid damage. Proactively conducting simple maintenance activities will allow your stormwater systems to accommodate their full capacity and reduce impacts related to high water and flooding.
These simple suggestions have the greatest potential to stop flood damage before it occurs. Many of these activities qualify as ‘maintenance to existing infrastructure’ and are exempt from the California Environmental Quality Act (CEQA); however, some of the activities may require permits from one or more regulatory agencies depending on the nature of the activity or feature being worked on. We recommend consulting with the appropriate lead agency to determine whether these actions are subject to CEQA review, or qualify as an exemption.
1) Sediment Basin Cleanout – Sediment basins are designed to capture sediments to maintain downstream water quality. However, over time, sediment builds up and reduces basin volume and infiltration rates. Excavating the sediments to return the basin to the as-built volume is an easy way to maintain capacity in your stormwater management system. Off-channel sediment basins that are part of an approved stormwater control plan are typically not considered Waters of the U.S. or State and typically do not require special permits from the regulatory agencies for routine maintenance. However, if basins do capture flow from federal or state waters, then maintenance permits may be needed for this work. Regardless of jurisdiction, any feature that may support protected species may need to be surveyed by a qualified biologist ahead of any maintenance activity to prevent impacts to the species.
2) Trash Grate Cleaning – Trash grates are relatively commonplace in municipal storm drain systems to prevent urban and suburban debris from clogging stormwater pump systems or entering receiving waters. However, if they are not regularly maintained, they may impair flood flows and exacerbate upstream flooding. Ensure trash grates are cleared before major storms and establish a regular maintenance program to keep them free of debris. This level of maintenance of a stormwater infrastructure system is not subject to regulatory agency permits.
3) Channel Maintenance – In California, storm drain channels come in all shapes and sizes. They may be earthen ditches, concrete channels, or realigned creeks that double as municipal stormwater conveyance systems. Regardless of the type, storm drainage channel maintenance is a necessity. Earthen channels perform best with smooth surfaces free of debris, vegetation, or other defects. They also need properly sized and engineered banks to prevent erosion and failure if overtopped during a large flow event. Concrete channels have a tendency to become potholed which provides an alternate pathway for stormwater flow. This can lead to erosion under the channel and cause severe damage to the structure including failure. Inspect earthen and concrete channels for any damage or irregularities and conduct repairs to reinforce any weak areas or patch holes as needed. Since many channels may be considered Waters of the U.S. or State, basic maintenance permits may be needed from the U.S. Army Corps of Engineers (Corps), Regional Water Quality Control Board (RWQCB), and/or California Department of Fish and Wildlife (CDFW) for certain maintenance activities.
4) Vegetation Clearing – While vegetation in drainage channels may be beneficial for some organisms, it can be a nuisance for public works departments intent on maintaining flood flows. Woody vegetation growing within a channel increases the channel’s roughness which slows flows and exacerbates flooding. In addition woody vegetation can trap other debris creating dams that even further back up municipal storm drain systems. Therefore, maintaining vegetation within a channel is a first line of defense for ensuring your stormwater system is functioning at capacity.
While the Corps does not regulate vegetation in wetlands and creeks, both RWQCB and CDFW typically do. The line between when a channel is a creek or not can be a gray area so it is best to consult with an expert to assist in the determination. If the vegetation targeted for removal is deemed to be riparian, then a maintenance permit from the CDFW is typically required. In addition vegetation along waterways may provide nesting habitat for birds. If the vegetation is removed during the non-breeding season (September 1 – January 31) there is reduced likelihood of disturbing active nests. However, if vegetation removal is performed during the nesting season (February 1 through August 31) then breeding bird surveys are recommended to prevent impacting nesting birds.
5) Fix Known Erosion Problems – Survey your property for evidence of problems in past winters and fix them now before large storms hit. Replace undersized culverts; repair landslides, gullies, and rilling; and clean storm drain inlets to avoid bigger problems during large storm events.
6) Stock Up on Materials – Have materials on hand to deal with erosion, landslides, or necessary water diversions. Sandbags, concrete edgers, hay bales, and straw-waddle tubing can effectively channel water away from structures or other sensitive areas to drainage areas. By directing flows to the appropriate receiving areas flooding can be prevented or reduced.
These are just a few of the ‘easy fixes’ you can do to ensure your stormwater system is functioning properly ahead of the winter storm season. Since all potential issues cannot be addressed through maintenance alone, some of the regulatory agencies offer emergency permits when immediate repairs are needed to protect life and property. Emergency permits are typically obtained fairly quickly, but the best course of action is to establish a regular maintenance program under a maintenance permit. This allows you to conduct annual maintenance without applying for a new permit each year. To find out more about when permits might be needed or how to obtain a maintenance or emergency permit, reach out to Geoff Smick for more information.