El Niño is back and
forecasters are predicting this winter impact to include “wetter-than-average”
conditions in California, Alaska, and the southern portion of the country. While El Niño cannot be prevented, we can
prepare for it by reflecting on our experience from other recent El Niño events.
Figure:
NOAA Precipitation Forecast
Based on our prior experience, we can expect landslides, widespread
flooding, bridge and stream bank scour, lots of road washouts and culvert
failures. It may take years to reconstruct what can be lost in a single large
storm event.
The temperature of a storm can have a bigger impact than the intensity
of the rainfall event during the heart of the winter season. Warm rains can
melt the snowpack, sending record breaking flows down rivers and streams.
Figure:
NOAA Temperature Forecast
Preparation and Planning
Every local agency should
have an “Emergency Preparedness Plan” to address storm damage preparation and identify the resources to respond.
A viable plan is essential in
the task of minimizing impact and maximizing response.
Minimize Impact
This can be accomplished through an effective and thorough monitoring and maintenance program. Severe storms can inundate drainage systems on their own, but if culverts, channels, and inlets are impaired, the effects will be much more severe. Potential upstream debris sources should be identified and abated if possible.
Review maintenance records to
identify areas that have experienced problems in the past. Those areas have a
high potential for future problems, particularly if the same repair strategy
was used repeatedly and failed.
Maximize Response
The creation of an accessible list of resources is essential to maximizing response. It is important to predetermine where to acquire supplies, equipment and work crews required to repair these facilities. Also, request 24-hour contact numbers for everyone on the list. The resource list should include:
· Suppliers - rock, asphalt, geotextile fabrics, pipe materials, barricades, “Road Closed” signs, K-rail, etc.
· Equipment - excavators, pumps and other equipment available at local rental or maintenance yards
· Prequalified contractors and consultants
· Disposal sites - landslide repairs often call for mass excavation
In order to insure a rapid response, it is important to have preapproved repair strategies. There are multiple techniques and products that can be used to repair various failures. Knowledge of these strategies will improve response times and design solutions.
Be familiar with all the permits in your area and the requirements. Most regulatory agencies already have an emergency permit process in place. Make sure your emergency is their emergency.
Response Planning
The elements of the Response
Plan includes: Assessment, Repair Strategy, Repair Implementation and
Restoration.
Assessment
Once a major storm event has
occurred, everyone needs to be aware of their roles and responsibilities. Most
public agencies already have a command structure set up through a local Office
of Emergency Services, which can be utilized for a storm damage response. The
first responders for a storm event will most likely be the police and the
public agency maintenance crews. The radio communication system used by most
police and maintenance crews provides the most reliable means of transmitting
the information from the field to the office.
Repair Strategy
Once the local area has been
assessed and the most critical areas identified, a strategy for repairs can
begin. For recommending the initial repair strategy the agency should use a
multidisciplinary team comprised of its own experienced staff engineers with
experienced civil, hydraulic, geotechnical, and structural engineer
consultants. The best solutions are multidisciplinary, since most failures
result from more than one simple cause.
Temporary or permanent
strategies for slip-out repairs may involve techniques such as rock buttresses,
steel sheet pile walls, cantilever retaining walls, gabion walls,
reconstructing slope with engineered/drained fill, or even road closure if
alternate routes are acceptable. The design team should be familiar with
preapproved design strategies. Consider innovative
strategies for recurring or potentially large-scale problems. Look at the big
picture and see what is happening in the watershed as a whole.
When developing strategies on
a site-by-site basis the team should consider the following factors, other than
simply the engineering solution:
·
Economics
of long-term vs. short-term repair strategies.
These include lifecycle costs, disruption from road closures and travel
delays during repairs.
·
Environmental
Constraints. Just because it’s an
emergency doesn’t mean the project is exempt from the law. Consider direct and
indirect impacts, loss of native habitat, water quality (NPDES requirements),
and permits.
·
Traffic
impact during construction. Staging of the work may require temporary signal
systems with generators in remote locations or low flow crossings at streams.
Repair Implementation
The project
implementation can be handled in several ways, using either maintenance crews
or contractors to reconstruct the facilities depending on the severity and
extent of the damages. Immediately following the event, contractors will most
likely be utilized on a time and materials basis. The less critical sites and
more highly engineered sites could be prepared for a competitive bid process.
- Agree on strategies to address community, agency and public needs
for giving and receiving information during repair activities (e.g.
delays, traffic control, sign packages, press releases). Consider using portable changeable
message signs.
- Ensure environmental compliance throughout repair with on-site
environmental monitoring.
- Consider time delays and configuration of traffic queues with
one-way traffic control.
Restoration
Once the repair has been
implemented at a site, whether temporary or permanent, it should be reviewed
for compliance with local and state safety standards or restored to its prior
condition.
For more information on storm
damage repair strategies, please contact Randell Harrison at:
Harrison
Engineering Inc.
399 Taylor Blvd. Ste 100
Randell Harrison managed a multidiscipline design team to deliver nearly $20 million in storm damage plans and specifications to construction within an eight-month period in 1997 and assisted the City of Concord with flood analysis in 2005. He is the principal owner of Harrison Engineering Inc., a civil engineering firm dedicated to providing, protecting and rehabilitating public infrastructure.