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The New Piura
The functional vision and mission of a less vulnerable city before El Niño.

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By Julio ernesto Gianella*
All the images provided by the author*

After March 27th, 2017's flood, there is the perception that Piura City's rehabilitation and rebuilding works will not resist any rain season.

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  neiter, 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 wishhes 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 invulneribility 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 superate 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  paralell to a life quality deterioration.

Piura City grew aside so between 1970 to 2017.

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:

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 occured 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, modyfing the  natural runoff what has increased considerabily 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-milimeter 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 waterproff 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 rainsease systems of rain drainage  with  side diches, drainss, or independent canals to waste water shewer, those lead in major courses as rivers, lakes, or the  sea.

Ath the Peruvian Northern Coast, this practice have been lost under the though 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 mycro-drainage, aplied to areas until 100 hectares or 247,11 acres, from the urban macro-drainage, applied to major areas.

These are the zones of Piura City with chances of flood from heavy rains or the Piura River's overflow.

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, posession, 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 sould be erradicated, relocating between 5000 to 8000 families.

The critical zones of Piura City are located in the historic downton (critical zone 2), the Soouthwest exit (critical zone 1) and the portion of Castilla City beside the Piura River (critical zone 3).

Critical Zones
From the previous vulneribility analysis, the zones  those would deserve  an attention as priority  related to the drainage   and the potential of future floods are identified:

Piura, January 2018: Rehabilitated lane not considering rain diches and drains neither.

A good example of rehabilitation work in the service lane at the auxiliar of North Pan-American (Prolongation of Sánchez  Cerro Ave.): Using cobble pavement  and side dich  with discontinued rowlock.

How did the city response?
The Piura's urban infrastructure -lanes, sidewalks, shewers-  has collapsed its big part. This situation is caused by the  most of pavements and wreckages built before 2017 el Niño event have not ccomplied  the quality standards, and tey did not  consider the urban rain drainage, anyway.

Before beginning works, it is necessary to measure carefully the benefits  of an inmediate rehabilitation with similar  characteristics to what tehre was, just in front of a superior quality, hig 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.

The Piura City's Puente Viejo, in 1925.

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 deppression  regarding to this zone is clearly delimited by  the level curve related to 35 meters or 115 feet altitude.

On the transversal diagram of the city's urban area (section in West-East direction, 100 meters or 328 feet to the North of  the Main Square), the deppression  is clearly visible, which lowest point is 7 meters or 22 feet below the intersection  point  with Tacna Street (calle Tacna), located to the East.

Extending  the deppression 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 is The Way Canal aligned to Sullana Avenue, in Piura City, that could prevent from floods to its historical downtown, and could ease the transit flow.

This project also presents the opportunity to turn into a spped 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 andd 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.

The oxidation lagoons currently serving to Piura City.

Waste water
Piura City's waste water, 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 largerly 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 waste water 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 writting by FACTORTIERRA.NET.
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 to include the credit.
Thanks to Arturo Peñaherrera Castillo for collaborating to this article.

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