Hope’s Property Management Department services and
Ascendant Neighborhood Development (AND) are two community-based not-for-profit affordable housing organization based in East and Central Harlem. Both organizations advocate for the preservation of affordable housing in New York City, "as rapid increases in market-rate residential and commercial development propel speculation, drive up rents, and encourage tenant harassment and displacement" (AND website). Just 22 percent of rental units in New York City are affordable to households whose annual income is below $30,000. Both organizations also work to strengthening the neighborhood's social fabric by assisting in the growth and success of local businesses, by assisting residents to enhance their lives and incomes, and by sponsoring community programs.
Hope owns over 1,300 affordable apartments in more than 78 buildings throughout Central and East Harlem (Community District 10 and 11). AND owns over 628 apartments in 28 buildings. During a meeting at the New School both Hope and AND expressed the need for evidence-based mapping to understand the exposure to flooding to their properties. Following a meeting with Hope, one of the main problems seems to be ‘blue sky flooding’, the type of flooding occurring without stormy weather and influenced by high tides at seas, high ground water table and surface elevation. There is evidence that this type of flooding affects basements, which are recurrently flooded, but for which Hope has very little funding for left over after what goes towards regular building maintenance. Moreover, Hope has been receiving a number of
violations from the ConEd, NYC's energy company, because as flooding affects basements, officers cannot access gas and water readings stored there. Because of these violations, Hope has been unable to close housing retrofitting deals with the for-profit-banks they partner with. At the same time Hope has been an early adopter of green rooftops thanks to funding made available by the city, however green rooftops address a different problem: they slow down excess rainfall but they do not slow down water coming from below.
GIS and remote sensing are critical tools for analyzing, preparing for, mitigating, and responding to natural and human-induced disasters, including from flooding events \cite{Huang_2009}\cite{Strobl_2012}. Geo-spatial technologies are used to estimate the risk of occurrence of a disaster based on physical and/or social dimensions. These two dimension are brought together in the concept of risk, which is a function of exposure, social vulnerability and the ability to recover of different social groups to flooding \cite{Ka_mierczak_2011}. Although there may be many variables influencing exposure to floods, here I refer to exposure as the susceptibility to being affected by an environmental related hazard \cite{Cutter_2005,Cutter_2012}, such as a flood event, based on area topography, proximity to the floodplain and rainfall trends.
An evidence-based small-scale mapping exercise for Hope would then need to make a case for the problems encountered by Hope by visualizing the hidden recurrent costs due to basement flooding as well as regular maintenance costs.