Morphological and Environmental Change Assessment: San Juan River Area (including Isla Portillos and Calero), Costa Rica

Transcription

1 Morphological and Environmental Change Assessment: San Juan River Area (including Isla Portillos and Calero), Costa Rica OVERVIEW OF ASSESSMENT AREA FOR SAN JUAN RIVER CHANGES NEAR SAN JUAN RIVER & LAGUNA LOS PORTILLOS Fruta de Pan Santa Rosa 3m Santa Isabel El Genizaro R I O I O I D N San Martin 5m 1.77 ha of tree cover RIO SAN JUAN 0.43 ha of tree cover Laguna Los Portillos Recent tree cover removed before 8 August m Colorado 170m R I O SAN J U A N 7m Colorado Guayabo New river channel constructed (8 August- 19 Nov. 2010) 132m 110m 190m R O CO I L O R A D O 3.46 ha of tree cover!l Area of active meander land removal & river redirection 19 November 2010 (Ikonos-2) The area has been environmentally stable over the past 30 years, with small indications of morphological change. There has been a decrease in the presence of small bodies of water; though, the general meander of the San Juan River appears stable with no dramatic changes or alterations of course. Legend "J!L Building / tent structure Area of active meander land removal & river redirection (Between Nov.-Dec 2010) Significant areas of recent tree cover removal, river dredging and new river channel creation were identified as occurring during the period from August to December 2010 between the San Juan River and Laguna Los Portillos New Channel constructed August - November 2010 Tree Cover removed (recent) before 8 August 2010 The depiction and use of boundaries, geographic and Research (UNITAR), providing satellite imagery names and related data shown here are not warranted and related geographic information, research and to be error-free nor do they imply official endorsement analysis to UN humanitarian & development agencies or acceptance by the United Nations. UNOSAT is a & their implementing partners. program of the United Nations Institute for Training Area of likely future meander land removal Tree Cover removed between 8 August - 19 November 2010 Report Analysis: Projection: UTM Zone 16N Datum: WGS-84

2 - - Morphological and Environmental Change Assessment: San Juan River Area (including Isla Portillos and Calero), Costa Rica By UNITAR/UNOSAT PREFACE: This report has been produced at the request of the government of Costa Rica using commercially available satellite imagery. ANALYSIS SUMMARY: A 30 year time series of satellite imagery dating from 1979 was reviewed for significant morphological and environmental changes in Costa Rica along the San Juan River area focusing on the areas of Isla Portillos and Isla Calero. Particular focus was made on identifying and analyzing important morphological and environmental changes since October 2010 over the area between the San Juan River and Laguna Los Portillos. Significant areas of recent tree cover removal, river dredging and new river channel creation were identified as occurring during the period from August to December 2010 between the San Juan River and Laguna Los Portillos; further there is apparently an area of active land removal on a meander bend of the San Juan River approximately 400m to the south of the newly created channel. If this meander land removal continues, it could redirect the flow of San Juan approximately 175m to the west, likely increasing river flow velocity downstream; such an increase in water velocity could also have the effect of accelerating erosion along the newly created river channel to the north. This preliminary analysis is based on a historic collection of low, medium and very high resolution satellite images recorded between 1979 and December 2010 and has not yet been validated in the field. ANALYSIS SECTION 1: OVERALL REVIEW OF ASSESSMENT AREA (MAP 1) A morphological review of the area was conducted using satellite imagery from 1979, 1986, and 2005, Analysis of the stream network indicates that the area has been environmentally stable over the past 30 years, with small indications of morphological change. There has been a decrease in the presence of small bodies of water, such as small ponds, in the southern section the area of interest. Though, the general meander of the San Juan River appears stable with no dramatic changes or alterations of course. ANALYSIS SECTION 2: CHANGES BETWEEN THE SAN JUAN RIVER AND LAGUNA LOS PORTILLOS (MAPS 2-5) Between the San Juan River and Laguna Los Portillos, the visible extent of the San Juan River bank appears to be stable with a healthy degree of vegetation cover. There are however, indications of recent vegetation removal in the immediate area. New growth can be seen and is visibly thinner than surrounding sections. The first very high resolution satellite imagery reviewed over the area was acquired on 8 August 2010; within it there are strong signature indicators of recent tree cover removal: hundreds of fallen or cut trees are visible, as well as disturbed top soil and probable localized fire burn scars resulting from small fires used to clear remaining brush. Although it is not possible to determine with certainty the date period that such tree cover removal occurred, it is a reasonable presumption that considering the relative lack of surface vegetation cover within the area of removed trees, and its rapid growth as identified in the satellite imagery of 14 November 2010, that the trees were likely cleared within 2-4 months preceding the acquisition of the 8 August imagery, thus placing the removal during the period of May-August Based on an analysis of satellite imagery recorded on 19 November and 14 December 2010, there is strong evidence to suggest that a new river channel leading from the San Juan River to the Los Portillos lagoon was constructed between August and November As of 8 August 2010 there were no signatures within the satellite imagery indicating the existence of an ephemeral stream to explain the appearance of this channel. There are also no apparent characteristic patterns of vegetation to suggest the presence of stream delineation as expected with an ephemeral stream activity resulting from seasonal floods. The San Juan River in fact currently remains stable with no signs of recent flooding in the area, ruling out ephemeral activity. However, there are strong indications of vegetation removal having occurred along the now existing channel path and the new entry point along the river bank. The new channel entry point along the river bank is consistent in shape and width with vegetation removal signatures identified in the satellite imagery recorded 8 August The channel course also follows the length of land where vegetation has been cleared. In addition, its course and banks are linear with a consistent width indicating artificial creation. The new channel has increased to an average diameter of 15m, showing a 5m increase between 19 November and 14 December This increase of channel width was likely due to erosion as new water flow cuts into the soil. Removal of vegetation along the channel has helped facilitate the erosion processes as it develops. This high rate of erosion is additionally facilitated with the high velocity of water flowing in from the San Juan River. As a result the banks of the channel appear to have also increased in width from the erosion process to an average of 23m in width. It is likely that as the water cuts through the soil, the existing banks will continue to widen as sediment washes out into Los Portillos lagoon. In the satellite imagery from 19 November and 14 December 2010 there is an apparent active attempt to redirect the San Juan River by straightening a meander approximately 400m upstream of the new river channel. In both imagery dates a large trench is clearly being cut into the meander. An apparent dredging boat is visible in both satellite image dates. From November to December 2010 the trench increased 22m in length to a total of 68m. If completed this cut in the meander will redirect the San Juan River approximately 175m to the west, and will likely significantly increase the water velocity downstream. Such a velocity increase will also increase the amount of water entering the new channel, thus likely widening the channel due to an acceleration of the erosion process resulting from the increased water velocity and inflow. Contact Information: Please send additions / corrections to :

3 83 45'0"W 83 40'0"W 83 35'0"W Fruta de Pan MORPHOLOGICAL AND ENVIRONMENTAL Santa CHANGE El ASSESSMENT Lanchón Rosa OVERVIEW MAP R I O I N D I O Laguna Benard Laguna Ebo (Los Encuentros) 3m Laguna de Harbor Head Santa Isabel Apalilí San El Genizaro Juan Del Norte (Greytown) San Laguna Taura Martin Laguna La Playuela Laguna La Barca Laguna Ciega 5m Area appears stable with no significant change in San Juan ( ) Development of an Oxbow lake Laguna Silico 10 50'0"N Section of river 7m has merged from a split into a single channel (between ) Laguna de Enmedio Laguna Agua Dulce 10 50'0"N San Juan river and side channels appear to be stable and show no significant alterations over 170m the past 30 years Laguna Pereira 7m Dramatic decrease of flow into side channel of the river 10 45'0"N Santa Isabel RI O S A N Colorado J U A N Laguna de Atras (Back Lagoon) Laguna Banana Laguna Limon BARRA DEL COLORADO Colorado Guayabo Laguna La Quebrada R I O C O LOR A DO 10 45'0"N D o s Laguna Leona B o c a s Laguna Samay d e l Co l o r a d o River bend has migrated 600m to the northeast ( ) R I O 132m Laguna Nueve C O L O R A D O Laguna Yaki 66m 10 40'0"N River meander has almost vanished 83 45'0"W... Airfield Laguna Cahue 83 40'0"W Decreased water levels and number for ponds in area '0"W 10 40'0"N Map Scale for A4: 1:175,000 Kilometers Track / Trail Spot Height (meters) The depiction and use of boundaries, geographic names and related data shown here are not warranted to be error-free nor do they imply official endorsement or acceptance by the United Nations. for Training and Research (UNITAR), providing satellite imagery and related geographic information, research and analysis to UN humanitarian & development agencies & their implementing partners. Report Analysis: Projection: UTM Zone 16N Datum: WGS-84

4 10 55'40"N MORPHOLOGICAL AND ENVIRONMENTAL CHANGE ASSESSMENT BETWEEN THE SAN JUAN RIVER AND LAGUNA LOS PORTILLOS (AUGUST - DECEMBER 2010) Sediment washout from San Juan River visible Laguna Los Portillos 1.77 ha of tree cover 0.43 ha of tree cover River channel partially obstructed by tree cover here Evidence of recent tee cover removal before 8 August Vegetation has begun to re-establish; likely removed between May-Aug.10 New river channel likely diverting portion of San Juan river flow northward into the Laguna Los Portillos San Juan River F No evidence of an ephemeral stream channel in area as of 8 August 2010 New river channel (approx. 15m diameter) likely constructed between 8 August and 19 November 2010 C a n o Increased erosion along channel bank was apparent between 19 Nov & 14 Dec. 2010, as channel water levels increased No significant increase in river water level is apparent (8 Aug.-14 December 10) S u c i o F Shape and size of new entry point is consistent with pattern of where vegetation removal occurred at the river bank. Mass removal of soil and dredging occurring along vegetation cleared area which will straighten the river meander. Trench increased 22m in length between 19 Nov & 14 Dec visible in satellite imagery 3.46 ha of tree cover!l 14 DECEMBER 2010 (IKONOS IMAGERY) Approximately 125m of land remains to be removed before the meander will be breached, thus diverting the San Juan River approximately 175m further west. "J Building / tent structure!l New Channel constructed between 8 August - 19 November 2010 emergencymapping@unosat.org Area of likely future meander land removal Area of active meander land removal & river redirection (Between Nov.-Dec 2010) Tree cover removed (recent) before 8 August 2010 The depiction and use of boundaries, geographic for Training and Research (UNITAR), providing names and related data shown here are not satellite imagery and related geographic information, warranted to be error-free nor do they imply official research and analysis to UN humanitarian & endorsement or acceptance by the United Nations. development agencies & their implementing partners. Map Scale for A4: 1:10,000 Tree cover removed between 8 August - 19 November 2010 Meters Protected Data: WDPA 2010 (UNEP) Report Analysis: Projection: UTM Zone 16N WGS-84

5 10 55'40"N 14 DECEMBER 2010 (IKONOS IMAGERY) Laguna Los Portillos Sediment washout from San Juan River visible 1.77 ha of tree cover 0.43 ha of tree cover River channel partially obstructed by tree cover here Evidence of recent tee cover removal before 8 August Vegetation has begun to re-establish; likely removed between May-Aug.10 New river channel likely diverting portion of San Juan river flow northward into the Laguna Los Portillos San Juan River No evidence of an ephemeral stream channel in area as of 8 August 2010 New river channel (approx. 15m diameter) likely constructed between 8 August and 19 November 2010 Increased erosion along channel bank was apparent between 19 Nov & 14 Dec. 2010, as channel water levels increased Shape and size of new entry point is consistent with pattern of where vegetation removal occurred at the river bank. No significant increase in river water level is apparent (8 Aug.-14 December 10) C a n o S u c i o 3.46 ha of tree cover Mass removal of soil and dredging occurring along vegetation cleared area which will straighten the river meander. Trench increased 22m in length between 19 Nov & 14 Dec Approximately 125m of land remains to be removed before the meander will be breached, thus diverting the San Juan River approximately 175m further west. Map Scale for A4: 1:10,000 Meters The depiction and use of boundaries, geographic names and related data shown here are not warranted to be error-free nor do they imply official endorsement or acceptance by the United Nations. for Training and Research (UNITAR), providing satellite imagery and related geographic information, research and analysis to UN humanitarian & development agencies & their implementing partners. Protected Data: WDPA 2010 (UNEP) Report Analysis: Projection: UTM Zone 16N WGS-84

6 10 55'40"N 1 NO EMBER 2010 (IKONOS IMAGERY) Laguna Los Portillos 1.77 ha of tree cover 0.43 ha of tree cover Evidence of recent tee cover removal before 8 August Vegetation has begun to re-establish; likely removed between May-Aug.10 New river channel likely diverting portion of San Juan river flow northward into the Laguna Los Portillos San Juan River No evidence of an ephemeral stream channel in area as of 8 August 2010 New river channel (approx. 15m diameter) likely constructed between 8 August and 19 November 2010 Shape and size of new entry point is consistent with pattern of where vegetation removal occurred at the river bank. C a n o S u c i o 3.46 ha of tree cover Mass removal of soil and dredging occurring along vegetation cleared area which will straighten the river meander. Approximately 125m of land remains to be removed before the meander will be breached, thus diverting the San Juan River approximately 175m further west. Map Scale for A4: 1:10,000 Meters The depiction and use of boundaries, geographic names and related data shown here are not warranted to be error-free nor do they imply official endorsement or acceptance by the United Nations. for Training and Research (UNITAR), providing satellite imagery and related geographic information, research and analysis to UN humanitarian & development agencies & their implementing partners. Protected Data: WDPA 2010 (UNEP) Report Analysis: Projection: UTM Zone 16N WGS-84

7 10 55'40"N A G S 2010 (GEOEYE IMAGERY) Laguna Los Portillos San Juan River Evidence of recent tee cover removal before 8 August Vegetation has begun to re-establish; likely removed between May-Aug.10 No evidence of an ephemeral stream channel in area as of 8 August 2010 C a n o S u c i o Map Scale for A4: 1:10,000 Meters The depiction and use of boundaries, geographic names and related data shown here are not warranted to be error-free nor do they imply official endorsement or acceptance by the United Nations. for Training and Research (UNITAR), providing satellite imagery and related geographic information, research and analysis to UN humanitarian & development agencies & their implementing partners. Protected Data: WDPA 2010 (UNEP) Report Analysis: Projection: UTM Zone 16N WGS-84

8 UNITAR/UNOSAT satellite solutions The UNITAR advantage Since its establishment in 1965, UNITAR has built a unique set of expertise, experience, knowledge and capacities to design and implement a variety of research and training activities. In keeping with its mandate to enhance the effectiveness of the United Nations in achieving the major objectives of the Organization the Institute contributes with concrete actions to developing the capacities of Member States in the fields of economic and social development, diplomacy, and peace and security Reaching out to beneficiaries UNITAR programmes provide training to approximately 80,000 professionals every year in some 200 different types of training activities, applying both face-to-face and distance-learning methodologies. Technology and satellite applications are gaining an important place in these activities as a growing number of UN and national entities adopt satellite derived geographic information methodologies in which UNOSAT, the Operational Satellite Applications Programme of UNITAR, excels since 2001 A challenging mission UNITAR mission is to deliver innovative training and conduct research on knowledge systems to develop the capacity of beneficiaries. Building on our experience, we optimize expertise, information and knowledge-sharing to achieve this mission. The specific mission of UNOSAT is to develop applied solutions and use training to make the UN system and member states benefit from space technology in the areas of human security and humanitarian relief, disaster prevention and territorial planning, and all other relevant areas UNOSAT: setting a new paradigm in satellite applications Since 2001, UNOSAT has delivered satellite solutions to relief and development organisations within and outside the UN system and member states to help make a difference in the life of communities exposed to poverty, hazards, and conflict or affected by humanitarian and other crises. Our skills are focused on satellite derived geographic information and data analysis. Our work record includes over 1000 analyses since 200, and 150 activations during humanitarian crises since UNOSAT is also a specialised training force with capacity to train national experts in situ or at headquarters in Geneva. For information and contacts: Unosat@unitar.org or