The New Piura
The functional vision and mission of a less vulnerable city before El Niño.
PIURA CITY, Peru - The knowledge we have not assimilated from Pre-Hispanic people is the urban planning. The best proof is that many of the cities built in the past are still there despite the natural disasters and the time lapse.
The city of Caral (Supe, Lima), the
most ancient of South America, was wisely built and it has not suffered from
floods , Nature's onslaugths neither, in 5000 years of existence.
The virtue of urban planning
is upon the balance between the what we want and what we can. If it has no
contribution of the vision and the wishes on a better future, we stay trapped
into more of the same; in the other hand, if it exceeds in futurist dreams, it
crashes into the reality and detracts.
That is why the main basis of
the Piura's future planning must be the non-vulnerability before the natural
phenomena, and our operative guideline must be the most rational use of the
available resources, not wasting but keeping the quality and the durability
of the investment.
In the other hand, we have to
keep in mind that the centralism in Peru is the main cause of the secondary cities delaying. To
realize that, let's compare the five major cities of this country to Colombia's,
taking a kind of closer example to understand how much back stepped-down we are:
Lima to Bogotá, Arequipa to Medellín, Trujillo
to Cali, Chiclayo to Barranquilla, and Piura to Cartagena
de Indias.
The three main cities in
Peruvian Northern -Piura, Chiclayo and Trujillo- might target to overcome a
million people each one, in 25 or 30 years up to come. The population growth of
Piura City is 3% annual in average - in 42 years it has gone parallel to a
life quality deterioration.
The Urban Expansion of Piura
The Piura City's Urban
Development Plan (UDP) was formulated by the province's municipality in 2014,
with a 18-year horizon to 2032. Although it is about a very well structured
document, the following questions on its insights are regarding:
- The predicted total urban area seems to be quite exagerated, because it could suppose to grow in 15 years more than four times the actual area.
- It does not consider the potential of urban home growth towards the North in direction of Piura-Sullana Axis (it only considers an industrial corridor).
- Piura will require in an upcoming future a civic-financial center at a big city scale, what I could not clearly identify in the plan.
- It keeps the actual location of Castilla Airport: as it has limited to a 2,4 km or 1,5 miles lane, it can not reach the international cathegory.
Between 1970 and 2017 the
Piura City urban area increased almost 150% coming from 16 sq km or 6 sq mi to
24 sq km or 9 sq mi, what means that population density (habitants per hectare
or hab/ha) increased from 80 hab/ha to 120 hab/ha (1 hectare equals 2,47
acres).
The areas of major expansion
potential are located to the East, in Castilla (included in the UDP), and to the
Northwest, in 26 de Octubre (not included in the UDP). In both cases, they
are about relatively high lands with good drainage and easy access by
Pan-American and Interoceanic Highways. The big limiting of the future
urban expansion will be the availability of water sources for human
consumption.
Why The City Flooded?
The easiest way is blaming the river and its overloads, when the human being is the main guilty who has modified and destroyed the natural conditions of that. First of all, the natural courses of the rivers must be respected and conserved, and the overflows occurred during the big overloads are not ever negative (as the case of Nile River and the natural fertilization of agricultural lands).
As the human settlements look for being closer to the rivers, because the advantage of water supply and communications feasibility, they make the conflict between the protection of the habitat and the water free flow.
In Piura City's case, the 1588's primal settlement, just more than 40 hectares or 98,8 acres, was located on a promontory upon the Piura or Lengash River (6 meters or 20 feet above its dryness level), and historically it did not suffered from significant floods until we have experienced in 2017. It also happens that the human being has destroyed the vegetal cover at the highlands of rivers' basins, modifying the natural runoff what has increased considerably during the rain periods.
Thus, the historical situation of Piura River has changed due to the action of human being:
a) Because of the destruction of the forests covering totally the Andean Range's West slope, and;
b) Because of the course modification, mainly through the rims narrowing.
When The Drainage Is Dismissed
The water flooding Piura City every El Niño event has two different origins, those require different type of forecast actions too: in one side we have the water accumulating from the falling rain directly over the urban area and surrounding mycro-basins, and in the other side we have the water overflowing from Piura River when the big overloads happen.
A 100-millimeter or 4-inch rain falling 10 continued hours, thing that is not rare if happens, can cause more than 50 cubic meters per second or 13300 gallons per second of runoff across the whole urban area located on the West Bank of Piura River (the primal Piura City, in other words). Due to the characteristics of roofs and pavements waterproof features, the hydrographic of the runoff at urban areas modifies evidently compared to the free land, increasing the peaks and disminishing the period of runoff.
Every city in the world built at geographic zones with medium to heavy intensity rains ease systems of rain drainage with side ditches, drainss, or independent canals to waste water sewer, those lead in major courses as rivers, lakes, or the sea. Ath the Peruvian Northern Coast, this practice have been lost under the thought that a heavy rain every decade (El Niño) would not be something to concern about, avoiding the maximum cost.
It is necessary to differentiate the urban micro-drainage, applied to areas until 100 hectares or 247,11 acres, from the urban macro-drainage, applied to major areas.
- The urban micro-drainage includes basically ditches, drains, or conductive irrigation ditches, those carry continously the water by gravity until the major system.
- The urban macro-drainage includes natural creeks, those must be protected or recuperated, and waterways built by the human being, that could be zanjon-type (Sullana's case), or tunnel-shaped, or infiltration galleries.
Zone Assignment Before Vulnerability
2017 Coastal El Niño confirmed
the existence, inside Piura City limits, of vulnerable urban zones what
certainly will be flooded by the future happening of that event, due to be at
levels below the river's overloads dimension. On Rebuilding with Changes Plan, it was chosen
the relocation of that zones' homes towards potentially non-vulnerable others
as policy, which implied the reservation, possession, and eventual expropiation
of the chosen lands for the moving, and the demolition and control of the
erradicated vulnerable areas.
Unfortunately there is a bit
done about this sense, except the re-settlement of a part of Lower Piura
Valley's rural population (Catacaos). It remains to solve urgently the problem of the
settled population at lowlands in the South (Piura) and
the Southwest (26 de Octubre) of the city, Gullman Avenue Axis' both sides,
where it is estimated 230 hectares or 0,88 square miles should be erradicated,
relocating between 5000 to 8000 families.
Critical Zones
From the previous
vulnerability analysis, the zones those would deserve an attention as
priority related to the drainage and the potential of future floods are
identified:
- Critical Zone 1: Gullman Avenue Axis' both sides enlarging 2,8 km or 1,7 miles towards the North from the crossroad with New Pan-American Highway. Human settlements might be totally erradicated of a 230-hectare or 0,88-square-mile approximate surface .
- Critical Zone 2: There is a natural land depression located 500 meters or 0,31 miles to the West of the Main Square, which lowest part is oriented along the axis descending from the North to the South. Inside this depression is Grau Club and its orientation coincides muchly to Sullana Avenue Axis. Here we have favorable conditions for easing a major structure belonging to the urban macro-drainage, through what could be tasked to evacuate fastly the water in floods case, rain origin and river's overflow as well, running the water down to the South for draining into the Piura River's course, at a point located in the dimension under the city level.
- Critical Zone 3: Castilla District. A big part of the urban zone is below the 30-meter or 99-feet altitude dimension and suffered from the flood due to river overflow on March 27th, 2017. Although there are protection dams on the river's rim, the problem is, according to technical reports, those dams could contribute to raise the dimension of the river's bed depth.
The Piura's urban
infrastructure -lanes, sidewalks, sewers- has collapsed its big part. This
situation is caused by the most of pavements and wreckages built before 2017 el
Niño event have not complied the quality standards, and they did not consider
the urban rain drainage, anyway.
Before beginning works, it is
necessary to measure carefully the benefits of an immediate rehabilitation with
similar characteristics to what there was, just in front of a superior quality,
high standards rebuilding. If the resources are enough, it is clear the second
one is the choice we should take.
Piura City's economic life
practically begins with the building of the old wood-&-iron bridge (Puente
Viejo) in 1893, which lasted more than a century. In Piura's case, the bridges
play a fundamental role in the urban development. If it is true the for existent
ones for vehicles in the city area have stood the big load of Piura River on
March 27th, 2017, they have not done the same efficiency. Cáceres Bridge
(Cuarto Puente) worked much more as a dam, increasing the overflow that finally
caused the flood of the city.
Cáceres Bridge was concluded
in 1995 not respecting rules of design, narrowing the river's course by
filling the river platform that existed at the East Bank (Castilla). It is an
excess of supporting vertical structures (6) and its flush is at the level
of the streets to access to. As a result, in March 2017, it
acted more like a dam instead of a bridge. As appreciated dramatically on the
photograph (excerpted from the report of University of Piura's Institute of Hydraulics).
Mid-2017, the Agriculture
Minister and the National Authority of Water's director stated that "the
non-mitigable high-risk marginal zone (of the rivers) can not be occupied, so
the Pecsa Oil Station and Open Plaza's parking lot those strangle Piura
River's course by Cáceres Bridge must be removed," however long months have
passed by and nothing of that was made.
In contrast to Cáceres Bridge,
the modern Bolognesi Bridge was concluded in 2001, after 1998 El Niño, by using
the best engineering, with a big metallic arc 130 meters or 427 feet horizontal
distance between the supporting spots, without intermediate supports, what
beared the last overload without any problem, not interfering the
river.
Bolognesi Bridge's cost,
made-in-Peru steele structure, was about US$ 7 million of 2001, what
considering the cost of living increase (51%), might not be over about US$ 11
million. Actual Bolognesi Bridge,
operating since 2001, replaces the one brought down by Piura River during 1998
El Niño. It is a good example of engineering.
A Canal Way For Te
Downtown
Inside the critical zone 2
previously quoted, it is located the core of the major commercial, civic and
cultural activity of the city, so it deserves attention as priority for the
purposes of urban planning and drainage. The natural depression regarding to
this zone is clearly delimited by the level curve related to 35 meters or 115
feet altitude.
Extending the depression
axis towards the North, going up Sullana Avenue, there are favorable conditions
for a major structure of urban macro-drainage what could concentrate the
evacuation of flood water across approximately 10-square-kilometer or
4-square-mile urban extension (almost 40% of actual area of the city in the
Piura River's West Bank).
The urban macro-drainage could
be 5,6 km or 3,5 miles length, could start at a nearby point to intersection of
San José María Escrivá (prolongation of Sullana Avenue) and Educativa
(prolongation of Chulucanas Avenue) Avenues, near Los Jazmines Neighborhood,
could run down along Sullana Avenue Axis Northwest-Southeast direction until the
Sánchez Cerro Avenue intersection, then South course to Las Palmeras
Neighborhood, and finally Southeast course for leading into the
river.
It could start at 41-meter or
135-feet altitude dimension and could finish at 26,6-meter or 87-feet altitude
dimension with a -0,27% average pendant. This project also presents the
opportunity to turn into a speed urban traffic car way to be used everyday,
every month and every year when flood problems does not appear, as happened in
Sullana with the Canal Vía, built successfully after 1983 El Niño event, what
works perfectly only if keeping clean.
The alternate use of the
macro-drainage canal for car transportation would represent a significant
contribution to Piura City's modernization. In the intersection of the
Sullana Avenue's Canal Way and Sánchez Cerro Avenue, that means the main khub
of the city, a by-pass bridge would be eased, what could relief the urban
traffic, significantly.
Piura City's wastewater,
located in the West Bank (not including Castilla) is conducted and poured
into the oxidation lagoons located in the Southwest of the city. Such lagoons have been
largely superated by the population growth and are based upon an open-pit
biological treatment technology, what is not convenient for a city getting
closer to the half-million people, less still for the next 30 years, what is
the horizon used when projecting sanitarian works of that magnitude.
It is also necessary to say
those lagoons are inside the property of Kurt Beer ecologic Municipal Park,
what is a contradiction. It is necessary to project a
new integral system of waste water conduction and treatment by using modern
technologies such as the built ones in Lima (Taboada and La Chira) and
Arequipa.
If we project with Taboada Plant's costs, (about US$ 150 million of 2012),
designed to attend 8 million people, a plant for Piura might not superate
about US$ 15 million, plus the cost of the trunk conduction pipelines. The new wastewater treatment
plant for Piura should be located at enough distance away from the city to avoid
any environmental problem, and to the South of course for allowing the
conduction by gravity.
Now or never, the rebuilding
of the Peruvian Northern has to be boosted. The months are running and the
people waits for but also desperates about. It is needed congruence (fruit of experience), urgency sense (fruit of commitment), honesty (what nobody doubts about), and a deep
respect to the people (what could be
lacking).
* Urbanist Architect. Based
upon the presentation offered to the Inundación Nunca Más Civile Association in
Piura, February 8th, 2018. Additional reports and writing by
FACTORTIERRA.
The images featured on this
article were provided by the author not identifying the source. If you believe
those images belong to you, please notify us at factortierra@gmail.com
to include the credit.
Thanks to Arturo Peñaherrera
Castillo for collaborating to this article.
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