Runoff Rethought in Byen Vann
BREAKING NEWS (April 18, 2064): Torrential rains battered Byen Vann on the
southwestern coast of Norway causing rivers of mud to rush down the mountainsides,
demolishing homes and real estate, disabling transportation, polluting water sources,
and disrupting civilian lives.
Downpours occur in Byen Vann 275 days a year, and inadequate stormwater
management results in frequent floods and mudslides. The seven mountains
surrounding this coastal city have elevations ranging from 300-3,200 feet with loose
soil grades and steep cliff faces. Eighty-eight inches of annual rain lead to
devastating mudslides contributing to erosion, poor water quality, and river
contamination. Urban development and impervious road surfaces cause floodwaters
to collect, resulting in oversaturated soil. Rainfall exceeds normal drainage capacity
on a daily basis. In addition, sewage and waste mixes with the mud, thus, causing
more contamination. Therefore, it has become crucial to prevent mudslides and
improve water management in Byen Vann to create a sustainable place to live and
provide economic growth.
Solving the problem of mudslides was critical to sustain the city. Mudslides
threatened lives, the economy, the environment, historical preservation, and
conservation of pristine landscape. Byen Vann’s civil engineers conquered the
problem by designing the four-step solution of Vegetation-Infiltration-RetentionDiversion (VIRD), an innovative process to prevent mudslides and enhance water
quality. (See fig. 1)
Figure 1- Segment of VIRD System
The first step, vegetation, consists of introducing rush plants and hardy bog
plants in mudslide-prone areas for bio-retention. The strong root systems reinforce
the unconsolidated soil matrix. Moisture probes in the soil measure saturation rates
of the soil. An array of weather stations provides representative readings of the
precipitation conditions of the entire area. The next lines of defense are infiltration
and retention. Strategically placed retention walls create temporary revetment
pools that collect water and allow infiltration. Excess water collects until it reaches a
height of three feet and then moves into the overflow. Next, the water drains into
raised boreholes and travels to below ground storage of abandoned limestone
mineshafts. To increase water infiltration, the engineering team injects liquid
carbon nano-tubes, which form around imperfections in the soil to minimize the
change to the soil’s grade. Once in the mineshafts, the water is filtered and detained
until needed. Through horizontal boreholes, it is transported into the city. Diversion,
the last step, directs overflow towards the river and into a mile-long pond site.
A multitude of technologies, including advanced bio-retention and diversion, are
needed in order for the system to function. Carbon nanotubes, allotropes of carbon
in a steroidal nano configuration, are injected into moist soil to break surface
tension and increase drainage. Next, advanced retention technologies are employed,
together with boreholes. Retention methods include flagstone retaining walls that
have a weir in the top lip for drainage to the next wall if the boreholes become
inundated. Finally, basic diversion technologies such as dams and drainage
channels, together with an off-site diversion pond, are implemented. The pond, a
modified version of a rain garden, is filled with stones and retentive water plants. In
order to utilize the water for drinking and bathing and increase sustainability, the
water sanitation engineers developed nano-sponges that absorb viruses and
chemicals from the mine water. While 75% of the sterilized water is siphoned and
distributed, one-quarter is left in reserve.
Community outreach and buy-in are critical to VIRD’s implementation; therefore,
Public Service Announcements (PSAs), digital newsflashes, and social media
advisories are distributed to residents, businesses, and builders. Trained
spokespeople and programs supplement the media campaign in community centers
and schools. Financial assistance and recognition programs for execution of storm
water Best Management Practices (BMPs) such as use of pervious surfaces, green
roofs, and eco-friendly drainage systems encourage compliance.
Increasing sustainability, VIRD’s environmental benefits include the dramatic
improvement of water quality, reduction of run-off, and increased infiltration. In the
past, mudslides would consume land, destroy infrastructure, clog waterways, and
kill residents and wildlife.
One potential risk is the failure of the highly complex Super-SCADA control
system, which relies on computers to operate all components of VIRD.
Communication or power losses could compromise the system’s functionality,
ultimately leading to soil saturation and causing mudslides.
The system is designed to handle a 100-year peak rainfall; therefore, a storm of
greater intensity could overwhelm the system. The water would then be diverted to
emergency holding ponds. If this were to occur, an evacuation alarm would be sent
to residents via communication bracelets and social media advisories.
To prevent this, geotechnical, hydrologic, and mechanical engineers created
redundancies with manually operated gravity overflows. The geotechnical engineers
assess soil properties, testing soil stability and assessing chemical properties of the
soil along with risks of certain slopes. Additionally, they design the retaining walls
making certain that structures are stable under soil conducts. Hydrologic engineers
control the flow of water as well as focus on water supply, distribution, treatment
and conservation. Mechanical engineers oversee the manufacturing of the
mechanical components, computers, and hardware.
Although engineers solved the critical problem, some trade offs were inevitable.
The initial investment for installation and labor costs to maintain VIRD is high, but
the payback is realized by maintaining an uninterrupted economy. Implementation
of retention technologies leaves scars on the topography and plant life of the
mountainsides. Eco-engineers devised a five-year creative plan to restore habitat
balance to its original state. The benefits of this solution to the community far
outweigh the limited tradeoffs.
The engineers of Byen Vann vanquished the century old problem of mudslides by
efficiently managing stormwater run-off with the VIRD system. This sophisticated
computer-based technology provides a safe and stable environment, sustainable
economy, and quality of life in Byen Vann.
(941 words)
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