Climate adaptation in urban areas: Water as a central building block

Cli­mate change pos­es a huge chal­lenge for munic­i­pal­i­ties. Flood­ing due to heavy pre­cip­i­ta­tion is becom­ing more fre­quent, while at the same time there is a threat of pro­longed peri­ods of heat and drought. Water plays a cen­tral role in the nec­es­sary adap­ta­tion to cli­mate change, espe­cial­ly in urban areas. The cre­ation of a nat­ur­al water bal­ance is just as much a focus as intel­li­gent water man­age­ment with a blue-green infra­struc­ture. The stor­age of water on mul­ti­func­tion­al sur­faces, in infil­tra­tion sys­tems and with green roofs and facades not only pro­tects against flood­ing dur­ing heavy pre­cip­i­ta­tion, but also secures the water sup­ply for parks, street trees and inner-city green spaces dur­ing dry periods.

Evap­o­ra­tive cool­ing con­tributes sig­nif­i­cant­ly to mit­i­gat­ing heat stress. “Water and urban green­ery are cen­tral build­ing blocks of cli­mate adap­ta­tion, for a healthy and liv­able urban land­scape, and for the preser­va­tion and enhance­ment of bio­di­ver­si­ty,” empha­sized Prof. Uli Paet­zel, Pres­i­dent of the DWA Ger­man Asso­ci­a­tion for Water, Waste­water and Waste, on the occa­sion of the pre­sen­ta­tion of the DWA posi­tion Water-con­scious devel­op­ment of our cities.

Design­ing the cities of the future in a water-con­scious way means a secure sup­ply of high-qual­i­ty and suf­fi­cient water, inten­si­fied green­ing as a heat and cli­mate pre­cau­tion and a man­age­ment of pre­cip­i­ta­tion water ori­ent­ed to the nat­ur­al water bal­ance with blue-green infra­struc­ture and mul­ti­func­tion­al land use. The water-con­scious city of the future clev­er­ly com­bines the inter­ests of water man­age­ment, urban devel­op­ment, road and open space plan­ning and cli­mate pro­tec­tion in terms of func­tion and design. Eco­log­i­cal­ly enhanced water bod­ies, banks and flood­plains are part of an attrac­tive urban landscape.

 

“Appro­pri­ate urban rede­vel­op­ment mea­sures are tech­ni­cal­ly fea­si­ble, eco­nom­i­cal­ly and eco­log­i­cal­ly ben­e­fi­cial, and legal­ly possible.”

- Prof. Math­ias Uhl, Chair­man of the DWA Coor­di­na­tion Group “Water Aware City of the Future”

 

This has been demon­strat­ed in numer­ous pilot projects through­out Ger­many. How­ev­er, real­iza­tion on a large scale often fails due to a lack of coop­er­a­tion between poten­tial project part­ners, legal uncer­tain­ties and fuzzy def­i­n­i­tions of finan­cial responsibilities.

One focus of the water-con­scious city of the future is the nat­ur­al water bal­ance. Ground­wa­ter recharge and evap­o­ra­tion must be strength­ened, and runoff from the city must be lim­it­ed to lev­els typ­i­cal of the land­scape. Land-sav­ing forms of devel­op­ment, water-per­me­able sur­faces, infil­tra­tion sys­tems, street and build­ing green­ery, cis­terns, and reten­tion ditch­es and basins are proven stormwa­ter man­age­ment mea­sures and must be giv­en greater con­sid­er­a­tion. Heavy rains and flood events require clear­ly iden­ti­fi­able emer­gency runoff paths in the ter­rain. In the future, green spaces, squares and sports facil­i­ties should be usable in a mul­ti­func­tion­al man­ner, includ­ing for the short-term reten­tion of stormwa­ter runoff.

Small-scale and usable pub­lic water areas in parks and in streets or even small flow­ing bod­ies of water, wet­lands simul­ta­ne­ous­ly bring qual­i­ty of stay, cool­ness and bio­di­ver­si­ty to the cities. Rain­wa­ter and also hygien­i­cal­ly safe waste­water treat­ed for spe­cif­ic uses can be used as water resources for irri­ga­tion. Green roofs or facades, tree plant­i­ngs, or water stor­age in open reten­tion areas can reduce par­tic­u­late mat­ter and increase cool­ing through evap­o­ra­tion. Alter­na­tive water resources can be used to irri­gate healthy veg­e­ta­tion with high evapotranspiration.

The appro­pri­ate mea­sures are already pos­si­ble on the basis of cur­rent law. The waste­water laws of the Fed­er­al Water Act and the state water laws give pri­or­i­ty to decen­tral­ized pre­cip­i­ta­tion water man­age­ment. Most of the fed­er­al states have stan­dard­ized con­crete require­ments for the per­mis­si­bil­i­ty or exemp­tion from per­mis­sion of pre­cip­i­ta­tion water infil­tra­tion and autho­rized the munic­i­pal­i­ties to order decen­tral­ized pre­cip­i­ta­tion water dis­pos­al. The Ger­man Build­ing Code opens up far-reach­ing pos­si­bil­i­ties for plan­ning urban green cor­ri­dors, also for the pur­pose of water-con­scious urban devel­op­ment, and for estab­lish­ing the nec­es­sary green spaces and plant­i­ngs in a bind­ing man­ner with regard to new devel­op­ment, also as com­pen­sa­tion for impact under nature con­ser­va­tion law. Urban devel­op­ment con­tracts offer exten­sive pos­si­bil­i­ties for reg­u­lat­ing water-con­scious design in large-scale projects.

Although the exist­ing law already opens up many pos­si­bil­i­ties, it must be fur­ther opti­mized in the sense of a water-con­scious city of the future. Among oth­er things, a clear legal man­date for the devel­op­ment of decen­tral­ized pre­cip­i­ta­tion man­age­ment should be stan­dard­ized in the Water Resources Act. In addi­tion, the fed­er­al states should cre­ate water law options for (co-)financing heavy rain­fall risk man­age­ment. This pos­si­bil­i­ty is not yet suf­fi­cient­ly pro­vid­ed for in the state water laws. In addi­tion, suf­fi­cient finan­cial resources must be made avail­able both for the plan­ning and con­struc­tion of the cor­re­spond­ing blue-green infra­struc­ture and for its long-term operation.