Term Report.Fm

December 7, 2012

Term report: Glacial lake outburst flood (GLOF). Palcacocha Lake, Peru.

Denny Rivas

A report prepared for the Geographic Information Systems course.

Environmental and Water Resources Engineering Program. University of Texas at Austin.

1. Introduction

Palcacocha Lake in Peru is a tropical glacial lake place. The failure makes water contained into the subjected to Glacial Lake Outburst Flood (GLOF) lake be suddenly released. The formed wave repre- risk. Knowledge about the behavior of an expected sents high risk for downstream population located GLOF event in Palcacocha is required to identify in the floodway. emergency strategies to prevent human life losses By using Geographic Information Systems (GIS) and major infrastructure damage in downstream and hydrodynamic modeling it is possible to asses areas. the flood evolution in time and space. The flood Due to climate change, retreating of glaciers is travel time from the lake to the downstream towns increasing rapidly. As a consequence, glacial lakes and its magnitude (extent, depth and velocity) can volume is growing as the ice melts and increases be determined combining both tools. The present the deposited water volume. Among the hazards analysis focus on designing a GLOF model based derived from the lake changes, floods have cata- on ArcGIS and Mike 11platforms applied to the strophic effects on nearby areas life. Palcacocha Lake case.

Such floods, commonly known as Glacial Lake 2. Study area Outburst Flood (GLOF), are caused by a failure in This report is focused on the Palcacocha Lake the natural dam (moraine) that holds lake water in region and its downstream areas, specially on Hua- Study area raz city, which is the main surrounding urban con- indicated that by 2009 it has exceeded 17 millions glomerate. m3. TABLE 1. Palcacocha Lake. Historical growing.

2 3 Max. Depth Year Area (m ) Volume (m ) (m) 1972 66,800 579,400 14 1974 62,800 514,800 13 2003 342,332 3,959,776 15 2009 518,426 17,325,207 73

The main risk concern about a GLOF event in Pal- cacocha is that Huaraz city is located 23km down- FIGURE 1. Location map. Palcacocha Lake. Ancash Region. Peru. stream from the lake. Cojup creek, whose origin is Palcacocha, drains into Quilcay River, which flows Palcacocha Lake is located at tropical latitudes in directly through Huaraz city before joining Santa the Southern hemisphere at 9º23’50”S and River. 77º22’54”W, at an elevation of 4567m. It belongs to the Cordillera Blanca in Peru and it is fed by the Historical catastrophic events precede current con- Palcaraju glacier. cerns about a new GLOF event in Palcacocha. In 1941 the end moraine failed, causing a flood that Despite the tropical environment in which the gla- destroyed part of what was a small Huaraz city. cier is immersed, elevations in andean mountains According to Carey (2010), 5000 people died are high enough to offer the climate conditions because 1941 flood. required by a glacier to arise and subsist. However, such conditions are becoming hostile due to climate change. Growing of Palcacocha Lake volume is an indicator of Palcaraju glacier melting and retreating.

Palcacocha Lake changes have been documented since 1972, indicating its volume is growing rapidly. In 1972 the volume was approximately 0.5 millions m3, while the last bathymetry measures FIGURE 2. Huaraz city covered by the 1941 flood.

Term report: Glacial lake outburst flood (GLOF). Palcacocha Lake, Peru. Pag. 2 of 8 GLOF modelling

In 1941 the lake volume was less than 12 million to obtain a spatial and temporal representation of m3. By 2010 it had already exceeded 17 million the flood flow over a map. m3. Otherwise, the critic volume has been esti- 3.2. Terrain model mated to be 0.5 million m3 (National Institute of Civil Defense, 2011). The modeling results can be just as accurate as the

Huaraz city has grown since 1941. It is now the input data. The best available terrain information capital of the Ancash region and its main touristic from Palcacocha-Huaraz area is a 30m resolution center. Its population has been estimated as ASTER1 Digital Elevation Model (DEM). 120,000 inhabitants (INEI, 2007). As the popula- Although partial LIDAR2 data was obtained, it tion and water volume has increased, the GLOF hazard has become higher than it was in 1941. covers just a fraction of the Cojup Creek length to be modeled. 3. GLOF modelling

3.1. Conceptual model

The adopted approach to reproduce a GLOF event in Palcacocha Lake is based on the creation of a terrain representation, over which hydraulic calculations are performed by a hydrodynamic model.

The results are produced and presented by the interaction between both models. It is a preprocessing - processing and postprocessing approach.

FIGURE 3. Coverage of available Lidar data The geometry inputs of the hydrodynamic model The magnitude of the event (flow depths of 10m are extracted from the terrain and the processed order are expected for peak discharges) reduces the results are overlapped on the same terrain in order impact of low terrain accuracy on calculations over

1. Advanced Spaceborn Thermal Emission and Reflection Radiometer (ASTER) is a space mission launched by Japan and United States agencies. Since 2011 the second version of the produced 30m DEM was released for public distribution. 2. Light Detection And Ranging (LIDAR) is an optical remote sensing technology. The gathered raw data did not contain the required statistical measurements (average point distance) to process it. Such measurements were estimated by using GIS tools.

Term report: Glacial lake outburst flood (GLOF). Palcacocha Lake, Peru. Pag. 3 of 8 GLOF modelling canyon shape intervals of the stream. However, on ing hydrodynamic model. A constant interval flat areas, the effect of terrain inaccuracy is between sections of 90m has been used to extract unavoidable. the cross sections.

To estimate the order of magnitude of the 30m DEM error in relation to high accuracy measurements, a new Digital terrain Model (DTM) has been built using the LIDAR raw data.

The mean square deviation between them is

135.32m2, which suggests the error of the elevation values of the 30m DEM is approximately 11.6m , FIGURE 4. Capture of the transect extraction interface which is high in relation to the expected depths The final discrete terrain model is composed by a (around 10m), but less than the official reported 24.6 km stream and 201 cross sections, which rep- average accuracy of global ASTER DEM (15m). resents Cojup Creek, from Palcacocha Lake to Thus, the 30m DEM has been used as the terrain Huaraz city limits. model, taking into account the final results will be highly susceptible to depth errors.

One dimensional hydrodynamic models require to transform raster represented DEM’s into discrete transects distributed along the stream axis. The transects and the stream axis has been extracted from the DEM using a preprocessing plug-in for

ArcMap called MIKE-GIS1.

The distance between transects is set based on the accuracy of the data, but also it is intended to be short enough to provide a smooth transition FIGURE 5. Cross sections extracted from the 30m ATER DEM. between cross sections. Such transition makes easy to find a stable numerical solution for the upcom-

1. MIKE-GIS is the geospatial component of the MIKE 11 by DHI package used for hydrodynamic modelling.

Term report: Glacial lake outburst flood (GLOF). Palcacocha Lake, Peru. Pag. 4 of 8 GLOF modelling

3.3. Hydrodynamic modeling is uncertain how a breach would form and behave on it. It will be assumed an overtopping failure, as The hydrodynamic calculations were performed suggested by Popov (1991), who proposed an using MIKE 11, a one dimension unsteady state empirical relation to estimate the expected maxi- model. Three components are required to define a mum flow for the GLOF as a function of the lake

GLOF process using such platform: lake volume, volume. The characteristics of the breach, includ- ing the time of formation, can then be adjusted to breach formation and the hydrodynamic parame- approximate the peak of the modeled GLOF hydro- ters of the streamflow. graph (dam break model) to the Popov’s equation

0.896 Lake volume. A bathymetric curve represents how maximum flow Qmax = 0.0048V , where the lake volume changes as a function of elevation. 3 Qmax = maximum flow m  s and V = volume

of the lake m3 .

Using the bathymetry data, the maximum dis-

charge is 14 445m3  s . The required formation time of the breach shape shown in Figure 7, under the established constraints, is approximately 30min.

FIGURE 6. Palcacocha Lake elevation - volume curve

Thus, it is related to the rate at which water will be released as the dam breach grows. A curve extracted from a bathymetry surface of Palcacocha FIGURE 7. Breach geometric characteristics Lake (National Institute of Civil defense, 2009) is Hydrodynamic parameters. To gain numerical sta- shown in Figure 6. bility, the simulation time step has been set as 1

Breach formation. There is no much information second and constant base flow of 200m3  s has about the moraine internal structure. It is known it been introduced as initial condition. A simulation is composed by debris, rock and ice deposits, but it period of 4 hours covers the entire GLOF process,

Term report: Glacial lake outburst flood (GLOF). Palcacocha Lake, Peru. Pag. 5 of 8 Results since the breach failure until the lake volume has The full time series raster is compressed by a mul- been completely drained. tiband file (dfs2 format), in which each band con- tains the results for each simulation time step. The selected resistance flow expression is Man- ning’s equation. The applied n coefficient is 0.005 as recommended by Chow (1959) for mountain rivers.

4. Results

Under the adopted dam breach formation hypothe- sis the arrival time of the flood to Huaraz urban area is 22 minutes, while the peak downstream discharge (maximum flow) is produced 33 minutes after the breach failure starts.

(a)

FIGURE 8. Huaraz city limits GLOF histogram

The water residence time, until the water is completely drained from the stream, is 70 minutes.

Spatial and temporal distribution of GLOF depth and velocity are represented as time series surfaces (b) (rasters). Figure 9 shows water depth and velocity FIGURE 9. GLOF stages at Huaraz city limits: (a) flood depth at arrival time, and (b) flood at flood arrival time to Huaraz city limits. velocity at arrival time.

Term report: Glacial lake outburst flood (GLOF). Palcacocha Lake, Peru. Pag. 6 of 8 Conclusions

Specific affected rural neighbors, located in the As long as flat terrain is not reached, the model floodway, are summarized in Figure 10 and Table . produces stable results. When floodplain is approached, before the junction of Cojup Creek and Quilcay River, results are not longer reliable. Therefore, model results are presented just for sections where they can be considered representative of the actual flood.

The plain area of Huaraz could not be modeled. However, the 1941 antecedent and the partial results show the susceptibility of Huaraz city to a GLOF event.

FIGURE 10. Maximum flood depth envelope and 5. Conclusions affected rural towns

The lag time since the peak discharge leaves the Although the applied approximations and inaccura- moraine and arrives to the downstream areas is 18 cies around the proposed model affects the reliabil- min. Therefore, the average GLOF wave celerity is ity of the results, the order of magnitude of depth, 82km h. velocity and time is enough to asses the hazard into

TABLE 2. Flood arrival time and maximum velocities which downstream communities are immersed. in Huaraz inhabited areas

Towns Arrival time Max. Velocity (min) (m/s) According to the results, there is no enough avail- Capulipamba and Unchos 19 48.5 able time (around 20 minutes) to perform an emer- Cantu and Cantun 20 25 gency evacuation plan once the GLOF has started. Huaraz Urban Area 22 20

Emergency structures (downstream engineered The catastrophic damage of the 1941 GLOF is dams) or reduction of the lake water volume are explained by the estimated velocities. A 20 m/s (45 measurements might be considered as solutions to mph) wave has enough power to knocks a person reduce the GLOF hazard in Palcacocha Lake. Fea- down even if it only comes up to the knees. A flood sibility studies for each alternative should be sup- of this nature gathers debris (trees, mud, rocks, ported by models similar to the presented in this etc.) and they create more destruction as they crash report. into other objects.

Term report: Glacial lake outburst flood (GLOF). Palcacocha Lake, Peru. Pag. 7 of 8 References

To predict the impact of a GLOF in the urban core Somos, M., & McKinney, D. C. (2011). Modeling of Huaraz city, a two dimensions model is recom- a glacial lake outburst flood (GLOF) from mended to extent results to flat areas. Moreover, Palcacocha Lake, Peru. Austin. the current model exclusively reproduces water flow, while the expected fluid is mostly a mixture of mud, sediment and water (debris flow).

6. References

Bajracharya, B., Bhakta Shrestha, A., & Rajbhan- dari, L. (2007). Glacial Lake Outburst Floods in the Sagamartha. Hazard Assesment Using GIS and Hydrodynamic Modeling. Mountain Research and Development, 27(4), 336-344.

Chow, V. T. (1959). Open Channel Hydraulics. (Caldwell, Ed.). New Jersey: The Blackburn Press.

Instituto Nacional de Defensa Civil. Peligro por aluvión en el departamento de Ancash. Hua- raz - Peru. Informe de Peligro No. 003-12/05/ 2011/COEN-SINADECI/15:00 horas. (2011). Lima.

Popov, N. (1991). Assesment of Glacial Debris Flow Hazard in the North Tien Shan. Pro- ceedings of the Soviet-China-Japan Sympo- sium and Field Work on Natural Disasters (pp. 384-391).

Silva, R. C. (2011). Procesos geodinámicos y peli- gros geológicos en los depósitos morrénicos de la laguna de Palcacocha. Universidad Nacional San Antonio Abad del Cusco.

Term report: Glacial lake outburst flood (GLOF). Palcacocha Lake, Peru. Pag. 8 of 8 LOCATION MAP 0 2 4 8 km Palcacocha Lake. Ancash Region. Peru Projection: Universal Transverse Mercator. Zone 16S Datum WGS84

Copap o Akillpo 1 Glacier Glacier o ilp qu Akillpo 1 A a da Glacier d a ra ra d eb eb n u Akillpo 2 u o Q Q H Glacier acu racy Pacliash . Yu Urus 2 Q Tocllaraju 1 Glacier Glacier Glacier Q. Y urac Urus 1 PERU Ca llacu Glacier Pucaranra da Quebra Tocllaraju 2 Glacier PALCACOCHA shinca ío ca I Glacier LAKE R hin Palcaraju Is Ishinca 1 Glacier Glacier Palcacocha Tullparaju Glacier

0 Lake

0 Ishinca 2 0

0 Glacier Pucaranra 2

6 Urayraju 2 9 Janyaraju 2 Tullparaju 8 Sources: Esri, DeLorme, Glacier Glacier NAVTEQ, TomTom, Intermap, Glacier Ranrapalca 2 Glacier ío y Jatunmontepunku R alta iPC, USGS, FAO, NPS, Glacier P Glacier NRCAN, GeoBase, IGN, Llaca 1 Kadaster aNL, Ordnance Wallunaraju a rad Glacier d ueb Glacier ra Q rec b p aru Ranrapalca 1 e ju hac Llaca 2 u o C Glacier Q C Glacier a d Tullparaju a r a b c Glacier e Carhuac 2 la u L Ucro Glacier Q Glacier Quebrada Cayesh 1 Callash Glacier Huamanripa 1

Glacier a c n Cayesh 2 a a u Glacier d h a y r a b c e l Churup 2 u a C Q Glacier Q . R acr Shallap 1 acr ure a Glacier c n Qu a 0 ebra r

0 d H a T 0 uella . ada 0 r p Q ueb ha a . 5 Q canc brad Q p 9 Yana Que lla 8 p ha Coju S a sc Huantsan 2 a C . Glacier Q Huantsan 1 Río Glacier Quilcay

HUARAZ

n CITY a h s n a C a t . n

a Q o í S R Tararhua Glacier Shacsha 1

ro Glacier . ta u Q u r c u u T r . u Q

0 P 0 0

0 Uruashraju 4

9 Glacier 8

Q R R Yanashallash . í u o C S r Glacier u o a

l n p t a a

Legend

Hydrography DEM: Elevation (m) ada ebr Qu uain RIVERS 2,100 - 2,600 tuch A . Santa Q LAKES 2,600 - 3,300 Catalina RIO SANTA 3,300 - 3,600 WATERSHED 3,600 - 4,600 Cities < 6,743 0 0

0 6"

0 CAPITALS

3 Pucaraju 9

8 URBAN/RURAL Glacier NEIGHBORHOODS

220000 230000 240000 TERRAIN DEFINITION 0 2 4 8 km Palcacocha Lake. Ancash Region. Peru Projection: Universal Transverse Mercator. Zone 16S Datum WGS84

Copap o Akillpo 1 Glacier Glacier o ilp qu Akillpo 1 A a da Glacier d a ra ra d eb eb n u Akillpo 2 u o Q Q H Glacier acu racy Pacliash . Yu Urus 2 Q Tocllaraju 1 Glacier Glacier Glacier Q. Y urac Urus 1 Ca llacu Glacier Pucaranra da Quebra Tocllaraju 2 Glacier shinca ío ca I Glacier R hin Palcaraju Is Ishinca 1 Glacier Glacier Palcacocha Tullparaju Glacier

0 Lake

0 Ishinca 2 0

0 Glacier Pucaranra 2

6 Urayraju 2 9 Janyaraju 2 Tullparaju 8 Glacier Glacier Glacier Ranrapalca 2 Glacier ío y Jatunmontepunku R alta Glacier P Glacier Llaca 1 a Wallunaraju a rad Glacier d ueb Glacier ra Q rec b p aru Ranrapalca 1 e ju hac Llaca 2 u o C Glacier Q C Glacier a d Tullparaju a r a b c Glacier e Carhuac 2 la u L Ucro Glacier Q Glacier Quebrada Cayesh 1 Callash Glacier Huamanripa 1

Glacier a c n Cayesh 2 a a u Glacier d h a y r a b c e l Churup 2 u a C Q Glacier Q . R acr Shallap 1 acr ure a Glacier c n Qu a 0 ebra r

0 d H a T 0 uella . ada 0 r p Q ueb ha a . 5 Q canc brad Q p 9 Yana Que lla 8 p ha Coju S a sc Huantsan 2 a C . Glacier Q Huantsan 1 Río Glacier HUARAZ Quilcay CITY

n a h s n a C a t . n

a Q o í S R Tararhua Glacier Shacsha 1

ro Glacier . ta u Q u r c u u T r . u Q

0 P 0 0

0 Uruashraju 4

9 Glacier 8

Q R R Yanashallash . í u o C S r Glacier u o a

l n p t a a

Legend Hydrography Terrain

RIVERS CROSS SECTIONS ada ebr Qu uain tuch LAKES LIDAR COVERAGE A Q. Santa lina Cata RIO SANTA DEM: Elevation (m) WATERSHED 2,100 - 2,600 Cities 2,600 - 3,300

0 6" CAPITALS 0 3,300 - 3,600 0

0 URBAN/RURAL 3 Pucaraju

9 3,600 - 4,600

8 NEIGHBORHOODS Glacier < 6,743

220000 230000 240000 GLOF MAXIMUM DEPTH 0 2 4 8 km Palcacocha Lake. Ancash Region. Peru Projection: Universal Transverse Mercator. Zone 16S Datum WGS84

Copap o Akillpo 1 Glacier Glacier o ilp qu Akillpo 1 A a da Glacier d a ra ra d eb eb n u Akillpo 2 u o Q Q H Glacier u yac Palcacocha rac Pacliash . Yu Urus 2 Lake Q Tocllaraju 1 Glacier Glacier Glacier Q. Y urac Urus 1 Ca llacu Glacier Pucaranra da Quebra Tocllaraju 2 Glacier shinca ío ca I Glacier R hin Palcaraju Is Ishinca 1 Glacier Glacier Palcacocha Tullparaju Glacier

0 Lake

0 Ishinca 2 0

0 Glacier Pucaranra 2

Glacier a c n Cayesh 2 a a u Glacier d h a y r a b c e l Churup 2 u a C Q Glacier Q . R acr Shallap 1 acr ure a Glacier c n Qu a 0 ebra r

0 d H a T 0 uella . ada 0 r p Q ueb ha a . 5 Q canc brad Q p 9 Yana Que lla 8 p ha Coju S a sc Huantsan 2 a C . Glacier Q Huantsan 1 Río Glacier HUARAZ Quilcay CITY

n a h s n a C a t . n

a Q o í S R Tararhua Glacier Shacsha 1

ro Glacier . ta u Q u r c u u T r . Jatun u Q 0 P Ruri 0 0

0 Uruashraju 4

9 Glacier

8 Micro Pampa Q R R Yanashallash . í u o C S r Glacier u o a

l n p t a Antonio a Raimondi

HUARAZ CITY

San Legend Francisco Miyururi Los Hydrography GLOF Max. Depth (m) Huaraz La Soledad Pinos RIVERS 0 - 3 ada Belén ebr n Qu uai LAKES 3 - 6 tuch A . Santa Q 6 - 9 Catalina RIO SANTA WATERSHED 9 - 12 Cities 12 - 16.8 6" CAPITALS 0 0

0 URBAN/RURAL 0

3 Pucaraju

9 NEIGHBORHOODS

8 Glacier

220000 230000 240000 GLOF MAXIMUM VELOCITY 0 2 4 8 km Palcacocha Lake. Ancash Region. Peru Projection: Universal Transverse Mercator. Zone 16S Datum WGS84

0 Lake

0 Ishinca 2 0

0 Glacier Pucaranra 2

Glacier a c n Cayesh 2 a a u Glacier d h a y r a b c e l Churup 2 u a C Q Glacier Q . R acr Shallap 1 acr ure a Glacier c n Qu a 0 ebra r

0 d H a T 0 uella . ada 0 r p Q ueb ha a . 5 Q canc brad Q p 9 Yana Que lla 8 p ha Coju S a sc Huantsan 2 a C . Glacier Q Huantsan 1 Río Glacier HUARAZ Quilcay CITY

n a h s n a C a t . n

a Q o í S R Tararhua Glacier Shacsha 1

ro Glacier . ta u Q u r c u u T r . Jatun u Q 0 P Ruri 0 0

0 Uruashraju 4

9 Glacier

8 Micro Pampa Q R R Yanashallash . í u o C S r Glacier u o a

l n p t a Antonio a Raimondi

HUARAZ CITY

San Legend Francisco Miyururi Los Hydrography GLOF Max. Vel. (m/s) Huaraz La Soledad Pinos RIVERS <10 da Belén bra ue ain LAKES 10-20 Q chu Atu Q. Santa 20-30 Catalina RIO SANTA WATERSHED 30-40 Cities <48.5 6" CAPITALS 0 0

0 URBAN/RURAL 0

3 NEIGHBORHOODS Pucaraju 9

8 Glacier

220000 230000 240000