The weak points of Piura

After a rainy season, we found a 2005 survey suggesting where rebuilding and prevention have to start. 

By Nelson Peñaherrera C 

Piura, Peru - Heavy rains fallen mainly in February and March 2017 left desolation and critics. In one hand, thousand of liters of water and sediment razed croplands, spoiled roads and flooded towns. In the other hand, the people started to accuse their authorities and officials of not surely anticipating to the event by preventive works and actions.

Rainy season that Piura Region lived was caused by an unexpected warm-up of Pacific Ocean due to El Niño Equatorial Current entry bringing warm water on. Southern Pacific Anticyclone simply collapsed  instead of pulling cold water from Humboldt Current, stopped blowing Antarctic wind,

becoming the sea more transparent, less salty and especially hotter. This accellerated evaporation, covered the sky with cumulus-nimbus clouds, produced heavy rains with strong wind and electric activity.

Rains and rivers' overloads flooded the lowest places, mainly in Piura Valley, those became to affect Piura City, the regional capital. There's not and explanation yet about why it was hard to forecast some weeks before.

Those effects  are not new and already had been warned in 2009 by a survey from Peru's Geological, Mining and Metallurgical National Institute (Ingemet in Spanish) , what made a large field assignment across the regional territory explaining its geology, risk zones, recommending prevention and mitigation actions.

Some years before, in 2005, Regional Government of Piura made a Disaster Prevention Plan for a 5-year term, that analyzed  potential risks in the same territory based on historical antecedents, detailing policies and activities addressed to avoid total and partial damages to the people, the infrastructure and the economic activities.

On May 8th, 2017, Peruvian Government launched a 3-year program called Rebuilding with Changes, that pretends to replace the operativity of whole Peruvian Northern. Although it was reported  there are already works projects for immediate execution, nobody clearly reveals where to start.

In our hand, we have combined the information by Ingemet survey, Regional Government of Piura's plan and the FACTORTIERRA coverage to set a first place list that could give the initial priority. More than 1,3 million inhabitants, equivalent to 70% of regional population, could be benefit. They live in 48 of the 65 districts Piura is.

1.- Piura Valley
It will be very difficult to specify what part is the most vulnerable because all seem to be. since many Andean rivers join to form Piura River, the problems begin for  approximately 949000 people living along the valley, those around 2 for every 3 are Piura Metro Area inhabitants, the regional capital city.

The speed powered by the Andean slope, the valley narrowness, the amount of water after a heavy rainy season produce floods  capable to destroy crop fields, towns and bridges. Salitral and Carrasquillo were rebuilt less than two decades ago, and they had to bear even being under very fast thousands liters of water temporarily.

As the river releases of Andean Range, already in coastal flats, continue to receive massive water flows, especially from creeks between Chulucanas and Tambogrande cities, increasing it too much that threatens Piura Metro Area, as happened on March 27th. Then, it floods Lower Piura Valley until leading in Sechura Desert.

According to Ingemet, the most critical point is Piura-Huancabamba Road, that is blocked by Seco and Serrán Rivers once they get overloaded by summer rains. In both cases, it was recommended to clean the courses, rebuilding and maintenance of badens. The deforested slopes can produce slides, for what house building and cropping in torrent flows were advised to avoid. 

For the course in lowlands, it was recommended to build river defenses for slowing down the erosion, especially when passing amid Piura and Castilla cities. Going down the flow, it was warned the maintenance and reinforcement of containment dams and river defenses to avoid flooding croplands in Catacaos and Cura Mori Districts, Sechura City inclusive, where the river leads once it filled Ramón Grande and Ñapique Lakes in Sechura Desert.

The good news for lowlands is the river has not changed its course since 19th century ending, but nothing is still said.

2.- Paita and Talara  Coastal Plateaus

Speaking in geological terms, what Piura knows as 'shore cord' was sea floor several millennia ago. In mid-Cenozoic, that floor started to elevate progressively creating a kind of an almost flat table emerging. Today is a big part of Piura Northern Coast surface, only interrupted by the Paleozoic Coast Range (formed by Amotape Mounts, Silla de Paita and Illescas Mount).

The flat is known as 'tablazo' in spanish or 'coastal plateau' and it's still elevating, what produces a rare landscape - a half-a-mile strip almost sea level that suddenly jumps up about 65 to 100 feet. It begins in Máncora at the north, ends in Gobernador Point at the middle of Piura shore. Itps only interrupted by dozen creeks leading in the sea, Chira River Delta and Sechura Desert.

Talara, Paita cities and their beaches circuits have been settled just between waves line and the elevation beginning, especially Cabo Blanco and Colán. In consequence every time it rains extraordinarily, creeks activate and cracks created in the plateaus slopes also form little streams leading into the sea. Although coastal plateau soil is basically sediment compounded with rounded little stones, it's necessary more water than usual for the material slices down not considering the erosion.

Paita and Talara historic downtowns are located precisely in those zones at sea level, and despite some creeks are canalized, they already were destroyed by the water and the mud - during the last 34 years, those low zones have been damaged by those agents precisely.

In Talara Province, many paths and roads connecting the beaches go through the base of the plateaus, exposing them before the same type of damage. Ingemet has recommended  containing nets and walls in some segments of slopes and badens with wide sewers in streams courses, those have to be checked out constantly to avoid their blocking by sediment and trash.

If whoever living on the plateau flat tops thinks to be save, could be mistaken. Because the torrents and slides  creeks begin on the high part, facilities and uptowns in weak compacting terrains could succumb as happened toa seafood processing plant in Paita and Sudamérica Neighborhood in Talara.

The recommendation  is monitoring constantly and relocation in mid term, especially in those places where erosion and the plateau elevation process  have destroyed wastewater pipelines, which flow are contributing to carve the slope.

Another critical segment is former Amotape-Negritos Road that runs in parallel to drinking water pipeline to Talara Province what could break and cut the flow off. Also the crude oil pipelines  pumped up from the underground in El Alto, Restín and Los Órganos could be significantly damaged. About 259,000 people live from Máncora to Gobernador Point.

3.- Lower Chira Valley

Although Chira River load is the double than Piura River, its neighbor, its erosive process is not acuted so much despite it has got to dig a big long ditch in the coastal plateau on its medium and lower course. Controlled since 1976 in Poechos Dam, an average summer for Chira River ever means a 1500 to 2000 cubic meters per second load, according to Chira-Piura Special Project official record in 2017.  However beginning April 1998, it became 7000 cubic meters per second, 75% more than Piura River maximum historical load.

Because of gravity, the valley's most vulnerable zone is is its lower course between Sullana and Paita Provinces borderline and its lead into the Pacific Ocean. About 41,000 people live straight there. According to Ingemet, the Lower Chira Valley is prone to floods because it's very flat. Overloads can also block the traffic between the two banks as happened in 1998 when destroyed Simón Rodríguez Bridge, close to a plant that pumps drinking water for Paita and Talara cities.

For the moment, rims have to be reinforced to avoid the erosion, and people have to be alert every time there is an official evacuation announcement. At least, the plateau is so close to get save.

4.- Huancabamba Valley

One of the most beautiful landscapes of Piura Andes, produced by volcanism, glaciation and a rare geological anomaly that unallowed it to elevate more than 12,870 feet altitude (known as Huancabamba Deflection),  is also a mortal trap if caution is not taken.

Officially sourced in Shimbe Lake, perhaps the most famous in Huaringas Complex at 10,560 feet altitude, Huancabamba River falls down free many times until forming a very narrow valley, V-shaped, from 8250 feet altitude in El Carmen de la Frontera District to 6600 feet altitude in Sóndor District , then becoming Piura/Cajamarca borderline  until turn east in Porculla Pass  (7260 feet altitude, in Huarmaca District) creating a deep canyon where the entire Andean Range's major depression is located. About 52,000 people live only in its middle course, if we add the whole valley inside Piura Region territory it raises 91,000 people.

Having a very steep surface, slides are common due to constant rains over the summits known as jalcas [pronounce "halkas"] or Piurano moors, caused by the violent shock of humidity from the Pacific and the Amazon Jungle. Even when the terrain is basically clay, it is not any warrant if deforested for roads, paths, croplands and many towns like Sapalache, Huancabamba, Sóndor or Sondorillo.

As a collateral effect already in the western side of the range, mudslides caused by rains can affect Canchaque and San Miguel De El Faique both located in Pacific slope. Crossing the range to the north there is another place in Pacaipampa District where the torrent slided down as much as a mile, Ingemet said. Coming back to Canchaque and next to Pusmalca River, La Afiladera (The Edger in english) is famous for being the detour to that town or San Miguel, and for its vertical clay-&-rock vertical wall that has already blocked Piura-Huancabamba Road sometimes.

Returning to Huancabamba Valley, if slides are not enough, enormous carves across the terrain can collapse the slopes. Many are caused by geological faults -the zone has a

quake timeline-  appearing one after one along the river course. The most notable runs down along Huáscar Street in Huancabamba City (6500 feet altitude), , opening wide toward the river as a stream.  The slipping has destroyed the pavement and it's belief it continues imperceptible day after day.

The only to do is containing the slopes where creeks have to be crossed and also disencouraging human settlements and agriculture on cracked zones. In La Afiladera case, a containing net was recommended to set upon.

Another threat for Huancabamba City, La Perla Neighborhood, its lowest place to be exact, is the river itself.  fed by a dozen of creeks, it can raise its level and flood as it was happened previous years ago.  For the moment, river dams and walls are the best defense means against the water, but  if the people give up to live in that zone, it would be better.  Some were relocated where the landing lane was projected (the neighborhood is called el Aterrizaje, The Landing in Spanish), but it begun another debate: where the relief is going to land in emergency case.

More Critical Spots

According to Ingemet and Piura Regional Government papers, other places where reabling and rebuilding are necessary: Sullana-Lancones Road due to mudslides and creek raising, Las Lomas-sapillica Road because of mudslides, Sullana-Ayabaca Road, and Ayabaca-espíndola Road especially where the detour to Aypate Archeological Site starts.

Although  it doesn't appear on the papers, Tambogrande-Chulucanas Road is ever broken by the creeks leading into Piura River. Nevertheless, phosphate extraction in sechura Desert is under threat every time it becomes La Niña Lake.

Piura second largest metro area, Sullana, has the adjacent blocks to Canal Vía as a main risk zone, that drives down Cieneguillo and Cola del Alacrán Creeks to Chira River creating a cascade. After more than 30 years working, a project is being proposed to reinforce, even remake, segments of the course now protected by cement slabs.

National and regional governments are not agree yet about the grand total caused by Coastal El Niño event across Peruvian Northern, but Macroconsult consulting firm calcullated it US$ 3,12 billion ending March, almost meaning 6% of gross domestic product. Former  Peru's President Pedro Pablo Kuczynski said there is enough money for facing it - many people is skeptical about. Will be positive changes after the rebuilding for real?

© 2017 Asociación Civil Factor Tierra. All Rights Reserved. The photographs featured on this entry are Miguel Chávez, Kevin Saucedo, Arturo Peñaherrera, Corey Godley, María Chero, and El Regional de Piura.