California’s 4-year drought may have further exacerbated rain- and drainage-related issues such as shrinking wood structures creating leak points; vegetation, debris, or sediment build-up that impedes drainage; and unnoticeable changes in upstream drainage patterns that may have downstream impacts.
To protect property and structures from costly erosion and water damage anticipated due to El Niño’s heavy rains, contractors, property owners, and municipal representatives should take a series of proactive measures.
The National Weather Service and other experts predict the current El Niño could potentially result in powerful, drenching rainstorms that can quickly create excessive flows and ponded water that erodes property, causing structural damage to foundations, concrete slabs, and other building structures.
On-Site Preparation
Drought-weakened trees can split or lose branches in intense rain events, creating hazardous conditions for adjacent areas.
Preparation is key to “weathering” this year’s anticipated storm events. Bryn Evans, Dudek senior project manager for stormwater projects, said “property evaluation is crucial to understanding potential erosion, sediment deposition and drainage-related problems before they occur.”
Property owners and contractors should evaluate landscaping and exposed slopes to assess the potential for surface flows that cause erosion. Drought conditions may also have stressed trees, particularly if irrigation has been reduced or eliminated, resulting in a higher potential for branch, limb, or whole tree failure.
“Trees must be managed like any other infrastructure asset,” said Mike Huff, Dudek senior project manager. This includes routinely inspecting them for signs or symptoms that they may include hazardous conditions. For properties with large or overhanging trees, a certified arborist can assess the relative risk to infrastructure from limb or tree failure in a wind or rain event, and can prescribe appropriate methods to manage this risk.
Owners should also evaluate areas of known ponding to determine whether drainage infrastructure needs cleaning or upgrades. Often, simple, inexpensive fixes can mean the difference between protection and damage. Steps to take include:
- clearing clogged landscape drainage pipes to allow water to drain from your property or project site;
- routing rooftop or other hardscape areas to permeable depressions or other vegetated areas to reduce flows and improve water quality; and
- readying a sump pump and/or sand bags for hardscaped or other areas where site drainage infrastructure is not easily modified.
Off-Site Evaluation
The invasive Mexican fan palm and other species can impede flows in degraded engineered channels.
Don’t overlook evaluation of off-site conditions for indicators of potential drainage and flow problems that may cause erosion or flooding. Adjacent properties may have been modified to direct flows away from upstream property and infrastructure without consideration of downstream effects. Additionally, undersized, inadequate, or degraded natural and engineered channels can accumulate sediment and vegetation that significantly reduces flow capacity during high-flow events.
Off-site condition evaluations can often be assisted by trained hydrology and hydraulic engineers and certified professionals in erosion and sediment control to evaluate potential risks.
As California braces for what may be a wild winter storm season, taking time to proactively evaluate your property or project site and adjacent storm conveyance systems may reduce flooding and damage risks. Trained professionals can often cost-effectively assist in evaluations and provide useful solutions to reduce impacts of runoff and flooding.
Bryn Evans is a Certified Professional of Stormwater Quality with more than 15 years’ experience working in the water quality and regulatory environment. For more information, contact him at bevans@dudek.com or 760.479.4143
Mike Huff is a senior project manager with 22 years’ professional experience with tree hazard evaluations and forest and tree inventories. For more information, contact him at mhuff@dudek.com or 949.373.8315.