‘Sponge cities’ soak up rain, pain

Early in­di­ca­tions sug­gest that a gov­ern­ment-backed cam­paign to in­crease the use of per­me­able ma­te­ri­als in con­struc­tion will help re­duce flood­ing af­ter storms, re­portHuMei­dong in Fuzhou, Liu Kun in­Wuhan and Hou Liqiang in Bei­jing.

China Daily (USA) - - CHINA - Con­tact the writ­ers through houliqiang@ chi­nadaily.com.cn

n ad­di­tion toana­part­men­tanda car, new­ly­weds in Wuhan have just one more ‘musthave’ item for their new lives: a boat.”

That’s just one of dozens of jokes that went vi­ral on the in­ter­net af­ter down­pours on July 6 flooded the cap­i­tal of Hubei prov­ince, leav­ing many roads im­pass­able. Pumps at 38 sta­tions across the city worked around the clock to drain about 100 mil­lion cu­bic me­ters of wa­ter, but still failed to pre­vent se­vere flood­ing.

On av­er­age, from 2013 to 2015 about 180 cities na­tion­wide suf­fered sim­i­lar floods, so a se­ri­ous ques­tion un­der­pins all the jokes: How­can we solve the prob­lem?

Tests in pi­lot ar­eas of Wuhan’s “Sponge City” pro­gram, launched last year, sug­gest the pro­ject­mayprovidean an­swer, but more still needs to be done, ac­cord­ing to ex­perts.

The pro­gram aims to al­low at least 70 per­cent of rain­wa­ter to soak into the ground in­stead of be­ing dis­charged into rivers. The de­sign­ers plan to achieve the tar­get by de­vel­op­ing res­i­den­tial com­mu­ni­ties fit­ted with stor­age tanks, fil­tra­tion pools and wet­lands, and by build­ing roads, side­walks and squares from per­me­able ma­te­ri­als.

In April last year, the cen­tral gov­ern­ment se­lected 16 cities and dis­tricts across the coun­try in­clud­ing Xi­a­men, Fu­jian prov­ince, and Wuhan as test grounds for the pro­gram. Each city was granted an an­nual sub­sidy of at least 400 mil­lion yuan ($60 mil­lion) over a three-year pe­riod. A fur­ther 14 cities were added to the pro­gram in April.

The pi­lot ar­eas in Xi­a­men and Wuhan have re­ported good feed­back. In­Wuhan, the con­struc­tion of 104 projects has started, buoyed by the in­vest­ment of 2 bil­lion yuan. Peng Bo, an of­fi­cial with the Wuhan com­mis­sion of hous­ing and ur­ban-ru­ral de­vel­op­ment, said the com­pleted sec­tions of the pro­ject per­formed ef­fi­ciently dur­ing a heavy storm on June 11.

“The rain started at 8 am. By about 10amithadesca­lated to a rain­storm that lasted un­til 2 or 3 pm. With­out the sponge city fa­cil­i­ties, the ac­cu­mu­lated wa­ter would have started flow­ing from the area about 10 to 15 min­utes af­ter the rain­storm, but our mon­i­tor­ing foundthat the­wa­teronly ob­vi­ously be­gan flow­ing out af­ter 11:30 am,” said Peng, quoted by Chi­naNewsweek.

If rain­wa­ter could be pre­vented Zhang Jian­ming, from flow­ing out for an hour or even 30 min­utes af­ter a storm, it would help to re­duce the amount of flood­ing, he added.

Ac­cord­ing to Zhang Jian­ming, deputy di­rec­tor of the sponge city de­vel­op­ment of­fice in Xi­a­men, 236 projects are sched­uled for com­ple­tion by the end of next year, at a cost of more than 7,200 mil­lion yuan. By the end ofMay, a com­bined 2.96 square kilo­me­ters in 59 projects had been com­pleted.

Wa­ter gar­dens

“No wa­ter­log­ging has oc­curred in the re­con­structed ar­eas dur­ing the heavy rains so far this year, even though Xi­a­men was hit by Typhoon Nepar­tak (a cat­e­gory-5 su­per typhoon),” Zhang said.

“The func­tion of the sponge city is huge in cop­ing with ur­ban flood­ing,” he said.

As an ex­am­ple, he cited a pro­ject near­ing com­ple­tion.

On Dec 9, the area around Xin­jing Road, which has been re­built with per­me­able ma­te­ri­als and wa­ter gar­dens that op­er­ate as stor­age ponds, was hit by a lengthy down­pour. While many roads in the area were­flooded, the­wa­t­er­around Xin­jing Road sub­sided quickly.

“To pro­mote the sponge city con­cept, we in­clude in­for­ma­tion about it in pri­mary school na­ture cour­ses, with spe­cially de­vel­oped note­books and dis­play boards,” Zhang said, adding that school-based fa­cil­i­ties will be used to pro­mote the pro­ject and en­cour­age stu­dents to ex­plore new ap­proaches to sponge city con­struc­tion.

Al­though Zhang stressed that the pro­ject will have to be com­pleted be­fore its ef­fec­tive­ness can be as­sessed, Peng, the of­fi­cial from Wuhan, was not op­ti­mistic about its abil­ity to cope with se­vere storms.

He agreed that the ini­tia­tive has been ef­fec­tive in relieving wa­ter­log­ging in some cities, but said the prob­lem will only re­ally be solved by im­prove­ments in the de­sign and con­struc­tion of drainage sys­tems.

“For cities in the south, whetherac­i­ty­will­be­flood­e­dor not af­ter heavy rain­storm still de­pends largely on its un­der­ground drainage sys­tem,” he said. Headdedthat the con­cept will only­be­truly ef­fec­tive­when rivers, lakes and wa­ter­logged ar­eas are con­nected ef­fi­ciently, al­low­ing wa­ter to flow away from flooded dis­tricts.

“The con­tri­bu­tion of each sponge in relieving wa­ter­log­ging is lim­ited, but if we can en­sure they are well con­nected, ev­ery sponge could play its role,” he said.

Peng’s re­marks were echoed byWang Ji­azhuo, a re­searcher with the China Academy of Ur­ban Plan­ning and De­sign, who is also a mem­ber of the ex­pert com­mit­tee guid­ing the con­struc­tion of sponge cities. “While pro­mot­ing the con­struc­tion of sponge cities, we should also pro­mote the con­struc­tion of drainage sys­tems and flood-preven­tion fa­cil­i­ties,” he told the busi­ness mag­a­zine Cai­jing.

Only the use of both mea­sures would re­duce ur­ban flood­ing ef­fec­tively, he said.

The func­tion of the sponge city is huge in cop­ing with ur­ban flood­ing.”

deputy di­rec­tor of the sponge city de­vel­op­ment of­fice in Xi­a­men, Fu­jian prov­ince

CHEN ZHUO / FOR CHINA DAILY

A man stands on top of a bro­ken-down car while pedes­tri­ans wade across a flooded road in Wuhan, Hubei prov­ince, af­ter a rain­storm on June 1.

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